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Mechanical

1954-62 Chevrolet 235 Power Glide Hydraulic Valve Lifters

Tuesday, January 30th, 2018

Very Important Cam Shaft and Valve Data

Occasionally when purchasing a used 235 high oil pressure engine, it may have been originally in a Chevy car with a Power Glide transmission. This will have a different cam shaft due to the Power Glide engine having hydraulic lifters. The lobes on the cam shaft must be a different height because of the lifters. In fact, hydraulic and solid lifters cannot be interchanged with non-related cam shafts!

To be absolutely sure if your 235 engine was originally from a Power Glide car do the following:

1. Remove the short side plate on the right side of the block.
2. Remove valve cover.
3. Loosen a rocker arm enough so one push rod can be removed.
4. Raise a valve lifter out of its resting place.
5. Place your finger in the valve lifter hole you have just created and feel for a
3/8” diameter hole on either side. Holes allow motor oil to lubricate and fill
the hydraulic valve lifter.

Engines with factory solid lifters will not have these 3/8” holes.

FYI: You can place a set of truck solid lifters with matching cam shaft in a 235 that originally came with hydraulic lifters. However, the reverse will never work! Without the 3/8” holes beside the hydraulics the lifters will not oil.

Valve Cover Trivia

Tuesday, January 30th, 2018

If you really like learning about old Chevy truck six cylinder history, this article is for you.

We recently visited Jerry’s Chevy Restorations in Independence, Missouri and noticed an interesting display on a side wall of his shop. Jerry has the complete series of Chevrolet “Stovebolt” six cylinder valve covers used on cars and trucks between 1937 and 1962. This 25 year display is even painted the correct gray color for trucks.

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No doubt it took much time cleaning, repairing, and painting to make them ready for their place in his restoration shop. Here is the order they were used in Chevrolet vehicles.

1937-38

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The two mounting stud grommets fit in a pocket below the surface of the cover. The valve cover must be removed to replace them. See the backside where the small metal strip secures the rubber grommet. (Not on 1940 and newer) Three necessary venting slots are on the top to allow the engine to breathe.

1939-48

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Redesigned with two larger attaching holes in cover so it is not removed to replace the mounting stud grommets.

1949-53

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New Idea: For the first time the add-oil hole is on the top of the valve cover. Now the mechanic did not add oil through the side engine draft tube. Good change! Less chance of some oil spilling as the oil container was placed down to the draft tube on the side of engine.

1949-53 – COE Trucks

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This different valve cover is used on the cab-over-engine “COE” trucks. Because the engine is under the cab, oil cannot be added through the top of the valve cover as with a conventional cab. Therefore, add oil hole is not punched but the spot remains where it is placed in a conventional cab of the same years. GM wanted no part of a gradual oil leak from a capped hole and it being so difficult to reach. The continual oil seeping would not be good for the truck owner or repeat new COE sales.

NOTE: The Chevrolet Master Parts Catalog for April 1, 1950 shows the buyer of a COE valve cover must purchase one for a conventional cab. The manual states it will be necessary to seal the oil filter hole with a thin sheet metal disc to provide clearance. Therefore, the photo in this article is of a pure factory GMC valve cover, not a modified unit altered by a dealer.

Of course, the Chevrolet Motor Division knew the chance of a protected valve cover under the COE cab would probably never need replacing. This pure COE valve cover was probably never not available!

1954-Early 55

The new high oil pressure 235 engine is introduced in trucks! Oil cap continues to be sealed as 4 small breathing slots are in a different position and are front to back on the top. This gives a place for the Chevrolet script lettering to be stamped on top. Good advertising.

Now, instead of 2 vertical studs with nuts for keeping the cover attached to the engine head, an overdue improvement is introduced. Four short machine screws press directly down on the new perimeter lip surrounding the valve cover. This presses on the valve cover gasket and stops oil leaks that occurred on the earlier design when the two studs were over tightened.

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Late 1955-57

More technology! To stop engines from sometimes leaking oil out of the 4 breathing holes on top of the cover they were removed! Breathing now occurred through a redesigned add-oil cap. It was used through the end of the series in 1962.

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1958-62

The add-oil cap is moved from the front to the middle. Because this 235 engine is tapered in its mounts to the rear and the new 1958 cars have a lower hood, GM moved it. This gave just a little more space and prevented hood contact with the oil cap.

NOTE: Because of the new center location of the add-oil hole, the Chevrolet script must be “half the size” on the valve cover top.

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Fan Blade Trivia for Most 216 Engines

Thursday, November 16th, 2017

One of the most important factors in successful engine operation is to keep the water at far below the boiling temperature. This is best done by matching the radiator with the fan blade.

On 1939-53 Chevrolet trucks there was a change in cooling fans depending on the demands the truck might have. The following three fan blade assemblies were as follows:

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15“ Diameter 4 Blades

Standard equipment on ½, ¾, and one ton. Matched with 3 core radiators.

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Before Restoration

18” Diameter 4 Blades

Placed on most 1 ½ and 2 tons. Matched with 4 core radiators.

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After Restoration

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18” Diameter Heavy Duty 6 Blade – Optional

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The Chevrolet Master Parts Catalog defines this fan “for use in low speed operations”. It was available on 1 ½ and 2 ton that would require slow moving or much of their RPM’s at idle speed.

Examples: A fire truck setting at idle speed while running the pumps to furnish water through their long hoses.

A flat bed farm truck during hot summer days. It slowly moves in a field while hay bales are loaded at almost idle speed.

No doubt at higher RPM’s this 6 blade fan would create extra wind noise under the hood but, after all, it was the price you paid to have a non-boiling radiator. (And it did the job successfully)

TEMPERARY FIX

Overheating ½ or ¾ ton? As calcium builds up over the years in engine and radiator, heating problems may surface. As a “Band-Aid” to get by for a while, some owners install the larger 18” fan. With more air passing through the radiator core, major repairs can sometimes be postponed.

1937 GMC Pickups, US and Canadian Differences

Friday, August 4th, 2017

Though 1937 GMC pickups were made in both Canada and the US, there is one major difference between them. They have very different engines. Here are some facts:

The 1937 US made GMC ½ tons used a flat head six cylinder engine from an Oldsmobile and in 1938 a flat head from Pontiac. These automobile engines were dependable with a proven record. This saved the egos of the US GMC dealers from trying to explain to customers why these “high-end” pickups were using the competitor’s engine.

In the US, the first year for the GMC ½ ton was 1936. They were all the longer 125 inch wheel base. The following year the GMC pickup was introduced in Canada and were made in the GM assembly plant in Oshawa, Ontario Canada. Just like GMC in the US in 1937, Canada offered a short wheel base 112” and optional long bed 125” wheel base. The Canadian Pontiac dealers were given this pickup to market alongside their car line. Unlike the US, there were no stand-alone dealerships for these new GMC pickups!

The long awaited introduction of the 216 six cylinder overhead valve engine was in 1937. It was used in Chevrolet cars and trucks in Canada and the US. This engine was quite successful for the existing roads in both countries. It was used in production Chevrolet vehicles 16 years.

When the GMC pickup first came on the market in Canada, it was given more horsepower than Chevys ½ ton. GM did this by adding a 216 Chevrolet engine with bored cylinders to create 224 cubic inches. This bore sizes increased from 3 ½” to 3 9/16”. Aluminum pistons also added more power over the Chevy cast iron units.

It appears the engineers designing the GMC pickup in the US wanted no part of using a Chevy engine for their first introduction into the pickup truck market. (GMC had previously been the big truck arm of General Motors). Because the Great Depression of the mid 1930’s GM needed to make emergency changes. Big truck sales in the US had reached such low numbers that something (a small pickup truck) had to happen quickly. Many US GMC dealers had gone out of business. Some were surviving only by repair work or selling additional products such as farm equipment, used cars and laying off employees.

In Canada financial disaster was not as imminent as there were no dealerships that sold only large GMC trucks. The newly introduced 1937 GMC pickup would not be marketed in a one marque location. GM of Canada used the new GMC to help the Pontiac dealers that were also feeling low sales. These dealers would probably be required to stock only a few GMC pickups and a basic supply of repair parts. After all, the Canadian Chevrolet car and truck dealer would also have a supply of new mechanical parts that covered all the items that the GMC pickup needed, except for aluminum pistons. Many of the Pontiac / GMC dealers would probably obtain the mechanical parts from local Chevy dealer and not wait for an order from Oshawa, Ontario of a week or more.

The big engine change for GMC in the USA was in 1939. Now GMC had developed their own six cylinder engine. All GMC pickups came with a 228 cubic inch power plant had overhead valves in the head.

1938-1953 Clutch Pressure Plate – WARNING

Wednesday, June 1st, 2016

When sending in your early GM truck pressure plate for rebuilding it is important to check the center of the spring diaphragm. It is amazing how many have been damaged beyond repair.

WHAT IS THE PROBLEM?

The sealed throw-out bearing is pressed against the center of the spring diaphragm each time the driver presses down on the clutch pedal. All operates just right as per the GM design until the throw-out bearing seizes internally. Now the face of the bearing cannot spin internally. The bearing face starts turning when it is pressed against the diaphragm. NOT GOOD! This metal to metal rubbing wears down the pressure plate. It can just go so long before even breaking a few of the 18 tips on the diaphragm. It the diaphragm tips wear unevenly, the total unit is a loss.

Check your diaphragm for damage in this area when it is removed from the vehicle. The attached photos show a worn diaphragm where the shiny metal is exposed. The shine is usually not a problem if created by a good throw-out bearing. This diaphragm was never made to be rubbed by a seized bearing. We suggest you always replace the throw-out bearing during clutch replacing. The older bearing may be ready to seize and begin ruining your pressure plate!!

IMPORTANT: The opening on the ends of a used diaphragm pressure plate will always have a shine. This is caused when the stopped throw out bearing makes contact with the fast rotating pressure plate diaphragm. For a split second the bearing is rubbing the diaphragm as “total contact” is made. If the bearing never seizes, there will be little more than a shine on the opening at the hole with diaphragm. It is the cut curve in the diaphragm tip that warns of a possible totaled assembly.

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Total Assembly

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Close up of the spring diaphragm

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“Shine” where bearing has rubbed diaphragm

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FYI:  The diaphragm out of the assembly

Engine Vacuum Leaks

Thursday, June 4th, 2015


Even the smallest vacuum leak on an internal combustion engine can prevent it operating to the level of its capability.

No matter how well you rebuild the carburetor, adjust the timing, or clean the gas tank, the engine will continue to operate below what it should even with a small vacuum leak.

On older engines a quick, easy way to check for leaks near the cast iron manifold will often uncover the problem.

    1. Place a large piece of cardboard behind the radiator cooling fan. See photo. This stops fan air flow in the area of the meeting point of the manifold, carburetor and engine head.1
    2. Use a spray can of starting fluid (available at auto parts stores). Let engine idle, and lightly spray in areas of where air flow will let into the carburetor through.2
    3. If you have even a small vacuum leak the starting fluid will be pulled incorrectly into the engine combustion chamber. The engine RPM will instantly increase. Your engine problem has been found! A new gasket or insulator plate will usually make all well.3

COE Shift Lever

Wednesday, June 18th, 2014

As vehicle owners begin to use their truck (cars as well) they report to local dealers of developing problems. Many things show up in long field use and not during short laboratory tests.
An excellent example is the 4 speed shift lever on the 1947-55 Chevrolet and GMC Cab over Engine “COE”. It was found that wear in the lower end of the vertical lever would develop. Even a little wear moved the top end of the lever closer to the dash until finally a drivers knuckle could actually touch the dash!
By 1950, a factory correction was made. The lever was shortened and moved away from the dash. Photos by Kent Zimmerman – Mesa, Arizona
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1947 – 50
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1951 – 55

Photos by Kent Zimmerman, Mesa, Arizona

1936 – 1938 Rear End Update

Friday, August 17th, 2012

A customer recently came to our shop with a big smile about his discovery on the changeover for his 1937 Chevy 1/2 ton. He had changed his engine to either a V8 or a 235 six-cylinder. The closed drive shaft system had to be removed!

After researching the local salvage yards, he discovered the perfect replacement. On a 2005 Chevrolet Colorado pickup, he found a rear end with 6 bolt drums to match his front originals. The leaf spring saddles were in the correct position. The backing plate to backing plate was only one inch wider (1/2 inch per side).

It worked for him, it should be correct for you if you update your driveline.

1938 GMC 1/2 Ton Engine

Tuesday, March 20th, 2012

It’s 1938 and the GMC division of General Motors is entering its third year of small truck production.  Prior to 1936, the GMC line consisted of only larger trucks normally bought by businesses and government agencies for heavy hauling.  The Great Depression was in full swing and GMC needed more sales to add to their financial bottom line.  To help sales and even save some of their dealers from bankruptcy, GMC began to market light trucks in 1936.

When GMC developed their first 1/2 and 3/4 ton pickups (T14 and T16), they had no smaller engines that would fit these light weight trucks.  They wanted no part of using the low oil pressure six cylinder engine in the Chevrolet trucks.  Knowing their own small light weight full oil pressure six cylinder was under development (to be introduced in 1939) they had to find a temporary engine.

The answer was in the Oldsmobile Division.  Their strong inline six cylinder flat head engine was just what GMC needed.  It was used for the three years prior to the introduction of GMC’s own overhead valve full pressure engine in 1939.

One exception to this rule was in the 1/2 ton 1938 pickup.  Possibly for economic reasons, the Pontiac inline six cylinder flat head engine was used in the small 1/2 ton during 1938.  It was hoped this would lower the retail price on the 1/2 ton just enough to help GMC dealers better compete with the small pickup competition that were all fighting for the limited sales during the depression years.

The following two photos show a rebuilt 1938 GMC engine owned by Ron Loos of Redding, California.  This Pontiac engine will soon be returned to his 1938 GMC.  The most interesting part of this engine block is the Pontiac Indian head crest cast in the right side.  GMC used it just as they bought it from the Pontiac Division of General Motors in 1938!

Photos by Ron Loos, Redding, CA

1938 GMC 1/2 Ton Engine 1938 GMC 1/2 Ton Engine

Chevrolet Engine Oil Pump Screens

Thursday, October 27th, 2011

In the days when car and truck owners as well as mechanics did maintenance, GM made these responsibilities much less complicated.  An excellent example was the screen below the engine oil pump.

Due to no oil filters and no detergent additive in the motor oil (to keep dirt in suspension), the oil pump screen was necessary.  Tiny dirt particles settled to the bottom of the oil pan as was expected.  The small dirt particles finally became dirt chunks stuck to the bottom of the oil pan.

GM wanted no chance that a chunk or clot of dirt might be drawn to the pump.  Thus, oil pulled into the pump had to pass through this screen.

These photos show several early screens used by various Chevrolet six cylinder engines.  Note the used screen on the 1937-53  216 engine.  Its rounded screen is held in place by a single wire.  The wire can easily be unhooked from the housing.  The screen then drops out for easy cleaning.

Chevrolet Engine Oil Pump Screens
1929-36
Chevrolet Engine Oil Pump Screens Chevrolet Engine Oil Pump Screens
1937-53 wire holding screen 1937-53 wire unhooked to remove screen

Casting Numbers

Thursday, February 11th, 2010
Casting Number Make Year CID
1970 Chevrolet 1964-1967 292
2135412 GMC 1946-1954 248,270
2193980 GMC 1952-1954 302
2324003 GMC 1955-1963 270
2324004 GMC 1955-1962 302
2404929 GMC 1955-1963 270
2192402 GMC Military 302
289890 Chevrolet 1963-1977 292
328575 Chev/Buick/Olds/Pontiac 1968-1984 250
328576 Chev/Buick/Pontiac 1968-1976 250
328880 Chevrolet 1963-1977 292
329990 Chevrolet 1963-1977 292
358825 Chevrolet 1966-1976 250
3629703 Chevrolet 1950-1952 235
366855 Chev/Buick/Olds/Pontiac 1966-1984 250
3692703 Chevrolet 1950-1952 235
3692708 Chevrolet 1950-1952 235
3692713 Chevrolet 1950-1952 235
3693374 Chevrolet 1942-1949 235
37001481 Chevrolet 1953-1955 235
3701946 Chevrolet 1953 235
3703414 Chevrolet 1954-1956 261
3733340 Chevrolet 1955-1957 261
3733813 Chevrolet 1958 261
3733946 Chevrolet 1954-1955 235
3733949 Chevrolet 1953-1955 235
3733950 Chevrolet 1954-1955 261
3737012  Chevrolet 1955-1957 261
3738307  Chevrolet 1958-1962 235
3738365 Chevrolet 1960-1962 261
3738476 Chevrolet 1958-1962 235
3738813 Chevrolet 1955-1963 261
3739365 Chevrolet 1958-1962 261
3739716  Chevrolet 1958-1962 235
3759365  Chevrolet 1959 261
3764476  Chevrolet 1958-1962 235
3769716  Chevrolet 1958-1962 235
3769717  Chevrolet 1959-1962 261
3769925  Chevrolet 1958-1962 261
3773949  Chevrolet 1954 235
3782856  Chevrolet 1962-1967 194
3782858  Chevrolet 1962-1967 194
378307  Chevrolet 1960-1962 235
3783949  Chevrolet 1953-1954 235
3788378  Chevrolet 1962-1974 292
3788406  Chevrolet 1962-1969 230
3788514  Chevrolet 1962-1970 153
3788813  Chevrolet 1955-1959 261
3789404  Chevrolet 1963-1976 292
3789412  Chevrolet 1963-1966 292
3789716  Chevrolet 1963-1972 292
3792852  GMC 1962-1966 194
3792858  Chevrolet 1962-1967 194
3821970  GMC 1967-1972 292
3833057  Chevrolet 1962-1970 191
3833067  Chevrolet 1963-1970 194
3833340  Chevrolet 1955-1957 261
383340  Chevrolet 1955-1957 261
3835253  Chevrolet 1942-1953 216
3835309 Chevrolet 1942-1949 235
3835335  Chevrolet 1942-1949 235
3835353 Chevrolet 1948-1952 216
3835363  Chevrolet 1954 235
3835374  Chevrolet 1942-1949 235
3835491  Chevrolet 1954 235
3835497  Chevrolet 1942-1953 216
3835527  Chevrolet 1951 216
3835692 Chevrolet 1950-1952 235
3835794  Chevrolet 1942-1953 216
3835846  Chevrolet 1953 235
3835849  Chevrolet 1942-1953 216
3835894  Chevrolet 1953 216
3835911  Chevrolet 1953-1955 235
3835917  Chevrolet 1954-1955 235
3835946  Chevrolet 1953 235
3835949  Chevrolet 1954 235
3836012  Chevrolet 1955-1957 261
3836223  Chevrolet 1955-1957 235
3836233  Chevrolet 1955-1957 235
3836340  Chevrolet 1955-1958 261
3836386  Chevrolet 1955-1957 235
3837004  Chevrolet 1955-1957 235-261
3837012  Chevrolet 1955-1957 261
3843363  Chevrolet 1953-1955 235
3850817  Chevrolet 1962-1978 230-250
3851656  Chevrolet 1963-1972 292
3851659  Chevrolet 1963-1976 292
3851859  Chevrolet 1963-1972 292
3854036  Chevrolet/Olds/Pontiac 1962-1976 230-250
3855914  Chevrolet 1963-1966 292
3855987  Chevrolet 1963-1971 292
3855991  Chevrolet 1963-1970 230
3856233  Chevrolet 1955 235
3858190  Chevrolet 1954-1955 235
3877178  Buick/Olds/Chev/Pont/GMC 1962-1978 230-250
3879875  Chevrolet 1962-1970 194
3886061  Chevrolet 1963-1966 292
3890011  Buick/Chev/Olds/Pontiac 1968-1972 250
3890013  Chevrolet 1968-1972 250
3892858  Chevrolet 1964-1967 194
389770  Chevrolet 1942-1951 216
3897702  Chevrolet 1942-1953 216
3921770  Chevrolet 1966-1976 292
3921967  Chevrolet 1964-1969 230
3921968  Chevrolet 1964-1976 230-150
3921970  Chevrolet 1963-1976 292
828575  Chevrolet 1972-1977 250
837751  Chevrolet 1942-1949 235
839770  Chevrolet 1942-1953 216
8397715  Chevrolet 1942-1949 235
839910  Chevrolet 1942-1951 216
839931  Chevrolet 1942-1949 235
8994256  Chevrolet 1964-1977 292
9890043 Pontiac 1968-1969 250

Fan Blade Change

Thursday, February 11th, 2010

At the beginning years of the 216 engine (1937-1938) the fan blade that cooled the radiator was made with a center hub plus four blades. Each blade was attached to the hub with three rivets.

This combination worked well when new, however, it was certainly more expensive to produce. A dangerous part of the design was the blades attached by rivets. Rain water while driving and sometimes a leaking radiator allowed dampness to get between the blades where they overlapped the center hub. As rust continued, the chance of a blade coming loose increased. Even with deterioration, the four blades stayed in balance while the vehicle was moving. Then all #*!# broke loose when a blade went through the hood, radiator, or where-ever!

A new design fan was introduced in 1939 and used through all the remaining 216 years and early 235 year, 1954. This blade was used on Chevrolet cars and pickup trucks. It is simply two identical blades welded together that held tight against the water pump with four fasteners. Much less expensive to produce and so much safer!!!

fan blade

Close-Up of 1937-1938 Fan Blade with Rivets.

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1937-1938 Fan Blade with rivets.

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Close-Up of the new improved safer 1939-1954 Fan Blade

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1939-1954 Fan Blade

1936 – 1946 Engine Dust Pans…Pure GM

Thursday, February 11th, 2010

1936 - 1946 GM

During the 1930’s and 1940’s our Nations roads were dirt and gravel. Paving had been underway for many years but there was still a long way to go.

To protect engine componants from a constant attack of dirt, GM designed metal stamped panels that attached to an area where the engine block and oil pan connect. This slowed dust from collecting on moving parts and for certain around the engine air breather.

1936 1946 engine dust pan 1936 1946 engine dust pan 1936 1946 engine dust pan 1936 1946 engine dust pan
1936
1936 ?
1937- 1938
1939-1946


Over the years, these gradually fell from their attaching fasteners and found their way to the roads. Potholes and ruts were often the culprits. The vehicle owners and even hired mechanics tended to remove them during maintenance. They were rarely paced back into position.

Today finding a pair of these engine dust pans is almost impossible. Newer generations have no knowledge of their existance. These photos of the different years should be about 1936 and 1946.

If someone is in disagreement on the years, email us at info@jimcartertruckparts.com

Early Gas Tank Changes

Thursday, February 11th, 2010

During the three years of this cab design, subtle changes occurred as GM engineers learned better ways to construct this truck. The gas tank changes on the pickup body style was probably the most obvious and it was different each of the three years.

In 1936, the new mid year low cab pickup continued with the earlier practice of securing the tank under the bed and behind the rear axle. The gas add spout extended through a hole in the lower bed side behind the right rear fender. Thought it might seem like a good location, it was not. Considering the trucks stiff suspension the poor roads of the 1930’s, and how rough trucks were treated, this location resulted in tanks leaks and cracked fuel lines that were over 6 feet from the engine.

The answer to this problem came out in the 1937 trucks. The tank was moved to the protected area under the cab seat cushion. This solved prior problems but the improvement did not go far enough. The fuel add hole was in the top of the tank on the passenger side. To gain access to the threaded plug to add fuel, the right side of a new split bottom cushion was raised or removed. Rain or shine, the passenger would stand outside and wait for fueling so the seat cushion could be replaced. Of course, any accidental spills or splashing from the spout would give fumes within the cab till the evaporation was complete. What if you lit a cigarette out of habit? What about a small electrical short under the dash? Your imagination can tell you what probably happened a few times over the years.

The engineers seem to have got it together in mid 1938. They redesigned the 1937 tank and cab so that gasoline was added through a spout that now extended out the cab corner. The bottom seat cushion was then one piece, however, for several months two piece bottoms were still used on the assembly line until supplies were exhausted. Therefore, the late 1938 tank was used less than one year and is very rare today. The new designed 1939 body style continued with this type tank and cab design but the 39 tank will not interchange in the earlier cab.

early gas tank changes 1

1937 ( above)

early gas tank changes 2

1937 (above)

early gas tank changes 3

1937 (above)

early gas tank changes 4

1937 (above)

early gas tank changes 5

1938 (above)

early gas tank changes 6

1938 (above)

early gas tank changes 7

Gas Spout Hole from Outside

early gas tank changes 8

Gas Spout Hole from Inside

Chevy and GMC Engines

Thursday, February 11th, 2010

Though the major cab and fender sheet metal change began in mid 1947 (Advance Design), both the Chevrolet and GMC trucks kept their same proven six cylinder engines as used in prior years.

The base engine in GMC light trucks was the 228 cubic inch inline six introduced in 1939. This overhead valve unit had a full pressure oil system with its rod and main bearings lubricated from drilled lines within the crankshaft. This high pressure is reflected on the dash gauge reading 0-50 pounds.

This family of engines during the Advance Design years also produced the 248 and 270 cubic inch units. The cylinder diameter in their main difference. They all share the same overhaul gaskets, water pumps, oil pans, distributors and side plates. On GMC, not Chevrolet, the cubic inch is the first three digits of the stamped serial number on the flat surface behind the distributor.

Chevrolet’s six cylinder used during most of the Advance Design years was very different from that in the GMC. Its standard 216 cubic inch engine was a result of continual improvements since the first Chevrolet six cylinder began in 1929. The 1940’s 216 truck engines were almost identical to that in the Chevrolet car. Therefore, millions of 216’s were on the road by the beginning of 1947. Their basic design and easy maintenance made them one of the greats in lower priced vehicles. When used on the roads of that era, they provided dependable service both on the farm and in the city.

The 216 was the standard power plant in the 3000 and 4000 series trucks. Its big brother, the 235 was optional on the 4000 series and standard on the 5000 and 6000 series. It is almost identical to the 216 but the increased displacement gave the needed extra power to work trucks. The 235 truck engine was not used in pickups, however, was matched to the Powerglide transmission cars with some modifications between 1950-53.

These 216 and early 235 are designed to operate without oil lines drilled in the crankshaft to lubricate their bearings.

The early 235 is not to be confused with the more famous later 235 full pressure engine first introduced in Powerglide Chevrolet cars and the Corvette in 1953. During this transition year trucks continued to have the lower pressure design. By 1954 the full oil pressure 235 became the standard of the Chevrolet fleet. It was modified for trucks by using solid valve lifters in place of the hydraulics in cars. The camshaft gear was changed from fiber to aluminum.

Closed Drive Shafts

Thursday, February 11th, 2010

Occasionally we hear owners condemning the closed drive shaft system used in the 1/2 ton trucks prior to 1955. After questioning the negative comment, we almost always discover the real criticism is the low gearing of the ring and pinion in the differential. Yes, this lower gear ratio was created more for slower roads of year gone by, but it is by far not a poorly designed system. In fact, it is questioned if there has ever been drive shaft and u-joint combinations that exceed the durability of this GM quality engineered closed unit.

Over 50% of the surviving older 1/2 ton pickups continue to use their original closed systems. Of these, the majority have had little or no servicing other than keeping lubrications in the transmission and differential.

Consider this when you realize the last GM closed drive shaft system was produced in 1954. Many others have been in irregular service prior to the 1920’s. Also remember that many 1/2 ton pickups were often given abuse far in excess of the manufacturer’s recommendations.

What modern open drive shaft system has been able to compare with this unsurpassed record? None!! Sure, the newer open u-joints are easier to change. They better be. They require attention or replacement so much more frequently!

Another Example of GM Quality!!!

We recently received the following comment from John Berkeley Ball. He also confirms the quality of the General Motor’s 1/2 ton closed drive shaft and differential.

Dear Jim Carter

Thanks for your excellent articles. One very pertinent point I feel that you should mention about closed drive shafts is their absolute impervability to rear spring wind up. Used on the farm over soft ground with heavy loads, you could not afford to send your rear end into drive breaking pulsations every time you lost traction, whether the shocks were worn out or not (some were single action any way). What a huge advantage over the Hotchkiss rear end! this is an often unknown design attribute that Chevy engineers were unfoundedly maligned for – at least by today’s city slickers…

John Ball

You may relate comments to this web site or Mr. Ball direct at john_ball@telus.net.

216 Oil Leaks

Thursday, February 11th, 2010

And now we’ve seen it all! A real example of American ingenuity.

Designed by an aftermarket company to keep an over tightened valve cover from leaking motor oil down the engine sides.  A metal band is pushed over and around the base of the valve cover.  Brass U-brackets are then secured by the two valve cover studs.  This creates equal pressure around the valve cover perimeter to stop the leaks down the side of the engine. 

Scott states he has seen these brackets on another 216 engine. Maybe a company in that area once offered them at local auto parts stores.

This photo was taken by Scott Golding, a resident of Western Nebraska.

216 Oil Leaks

E-mail scottandbetty@hotmail.com. Scott states he has seen these brackets on another 216 engine. Maybe a company in that area once offered them at local auto parts stores.

Your opinion is welcomed.

 

1937 or Older Chevrolet Pressure Plate

Thursday, February 11th, 2010

1937 Chevrolet

Rebuilding the 1937 and older pressure plate can be a little tricky. The early design (activated with a carbon throw out bearing under pressure) requires extra steps when being rebuilt. With the help of an older shop manual (see below) the final details can be successful.

The personal letter is from Richard Wright of Westtown, NY. He did not receive the necessary final touches in the rebuilding procedure and he made the final adjustments. Fortunately, the 1935 Chevrolet shop manual has a description of how to complete this procedure. The following letter, pictures and shop manual page should be of help in the rebuilding procedure. A more advanced pressure plate was introduced in 1938. A new diaphragm design then became a standard in Chevrolet for 30 years.

NOTE:

The “X” mark on the clutch cover should be lined up as near as is possible with the “X” mark on the flywheel. These “X” marks are balance marks.

Place clutch pilot tool, Fig.99 into position. This tool properly lines up to the disc so that when the transmission is assembled the splines on the main drive gear shaft will line up and enter easily the splines in the clutch disc.

Assemble the nine cap screws holding the clutch cover to the flywheel, tightening each one , one turn at a time until the cover is assembled into position. Remove the clutch disc aligning tool. Assemble throwout bearing sleeve.

CLUTCH LEVER HEIGHTS

It is very important that the clutch levers be of the same height to assure correct clutch operation. In addition to the clutch levers being the same height, the maximum run-out of the clutch throw-out bearing plate should not exceed .020″ when measured with an indicator guage placed on the clutch housing.

clutch adjustments 1937 chevrolet

The checking and correcting may be done after the transmission and clutch throw-out collar have been removed.

To check run-out, place the indicator guage on the clutch housing through the transmission hole as shown in Fig 100. Set the dial guage at zero and check run-out while turning engine. If run-out exceeds .020″ the high lever plate should be shimmed-up by placing a shim under each side of the plate at the attaching bolts, which will result in dropping the high finger. Connecting rod shims with the ends trimmed may be used.

REPLACEMENT OF TRANSMISSION

These operations are just the reverse of the removal operations. The tool shown in Fig 101 can be used to hold the universal joint rings in position while assembling the nuts.

1937 clutch adjustments chevrolet

CLUTCH PEDAL ADJUSTMENT

There are two very important adjustments to the clutch pedal. The first is for obtaining the proper clearance between the clutch pedal and the floor board and the second for obtaining 1″ of the pedal travel before the clutch begins to disengage. These two adjustments compensate for wear of the clutch parts, and if these two operations are performed when necessary, long trouble free clutch operation can be expected.

1937 clutch adjustments chevrolet

To obtain 1/2″ clearance between the clutch pedal and the floor board, loosen nuts “A” and “B” in Fig 102 and move the pedal stop either forward or backward until the clutch pedal clears the floor board 1/2″


1937 Chevrolet 1

1937 Chevrolet 2

1937 Chevrolet 3


Below is a letter from Richard Wright of Westtown, NY.

1937 Chevrolet 1937 Chevrolet

1938-1953 Clutch Disc

Thursday, February 11th, 2010

Chevrolet introduced their basic nine inch single disc clutch and corresponding diaphragm pressure plate in 1938. This pair was used in their cars and most 1/2 ton pickups with three speed transmissions through 1953. With about one million of these vehicles sold annually, one can quickly realize the high numbers of this clutch system that was at one time on the highway.

Even in 1954 with the introduction of the larger 10 inch clutch disc and modified pressure plate on the new 235 six cylinder, the original design continued to sell very well as aftermarket replacements. Today, they still have a strong demand even though the majority of these over fifty year old vehicles are history. Most auto part stores now keep a pair in inventory for their walk-in customers.

1938-1953 Clutch

To add even more validity to this clutch’s durability, GM reintroduced it in the late 1960’s. General Motors was a major producer of full size passenger buses and the demand for most having the optional air conditioning was becoming strong. Almost all new buses would now be equipped with the option. The original small nine inch clutch was combined with the newly engineered large bus AC compressor. Once again, this proven clutch was serving automotive needs!

Therefore, if you find a source for new or core clutch assemblies used from the late 1960’s to at least the mid 1970’s in GM buses, they will also fit 1938-53 cars and small trucks.

Non Detergent Motor Oil in Older Engines – A Must!

Thursday, February 11th, 2010

Prior to about the mid 1950’s, motor oil did not have the modern detergent additive we have today.  Therefore this type engine oil didn’t keep dirt particles in suspension. Foreign material would slowly settle to the bottom of the oil pan and on other flat surfaces such as the valley of the head.

If you ever removed an oil pan from a 60 year old engine that has been setting, chances are good there can be up to 1/4 inch of sludge in the bottom. This is not a bad thing! The non detergent oil has allowed the dirt to settle. As most 60 year old engines did not have an oil filter, this dirt settling was what should happen to increase the engine life.

The problem begins when a new owner wants to get his old vehicle running. He installs plugs, points, back-flushes the cooling system and changes oil. Oops, he probably adds detergent motor oil! The dirt deposits now begin to slowly go back into suspension and your engine life is shortened. Unfortunately with no oil filter the dirt stays in the oil and shortens the remaining life of the engine.

Moral: Always use non-detergent oil if the engine has no oil filter.  Most auto parts stores carry this type oil, however they usually keep it on a back shelf.  Ask the counterman what you want.  The price is even less than detergent oil!

Muffler Tech

Thursday, February 11th, 2010

muffler tech

Prior to about 1962, Chevrolet trucks were equipped with round straight through mufflers. These units reduced back pressure and allowed the engine to breathe to its full potential. This caused a little extra exhaust noise in comparison to the larger more engineered oval car mufflers but trucks were for work and power.

About 1950 truck mufflers were given slightly larger inlet and outlet pipes. This allowed increased air flow which related to the slightly larger carburetor installed that year.

During the late 1960’s the Chevrolet truck Master Parts Catalog no longer listed mufflers. It appears they discontinued these units and left them to be provided by auto parts stores. By about 1995 the larger 1950’s straight through muffler was the one style available and any remaining older pipes were modified to fit 2″ inlet and 1 7/8″ outlets. Length is about 20 ½ inches.

The cars were lower to the ground and thus, required an oval muffler.  This oval shape allowed it to be higher and less likely to hit an object on the road.  Trucks were high and a round muffler was satisfactory.

Correct copies of these mufflers are available from Jim Carter’s Classic Truck Parts and a few other full stocking GM truck dealers.

 

Okie Bushing Installation (Just Before Installing)

Thursday, February 11th, 2010

okie bushing

The Problem

The closed drive shaft ( on GM 1/2 ton, 1937-54) is supported at the front by two bushings. As these wear egg shaped over many miles, the drive shaft begins to move up and down. This ruins the grease seal and causes the u-joint to begin rubbing the “bell”. Thus noise and vibration!

Finally, with a bad seal, the differential fills with transmission grease running down the drive shaft starving the shifting gears. Then, the rear wheel seals leak, the brake shoes become oil soaked, and finally the u-joint flies apart from rubbing the bell.

The Solution

Catch the developing problem early and save much expense and down time. Install what is sometimes called an “Okie Bushing”, an aftermarket, produced originally in Oklahoma. This is a non-GM repair used successfully since the 1950’s.  This is a quick, permanent fix that does not require tearing down the differential!

Instructions

Remove the u-joint bell retainer and slide this bell back, exposing the u-joint assembly. Disassemble the u-joint by removing the four bolts. The rear u-joint yolk can now be slid off the 17 drive shaft splines, exposing the grease seal in the drive shaft.

Pull out this seal and the front egg shaped bushing from the torque tube. Sometimes this bushing is difficult to remove and special pullers can be rented. Otherwise, call Jim Carter’s Truck Parts at (800) 842-1913.  They have these pullers made.

Press in the long Okie bushing – seal first. Placing a wood block over the bushing end and tap into the drive shaft housing (torque tube) with a hammer.  This action will then press the other original rear bushing back out of position. The new Okie bushing will now hold the drive shaft in perfect alignment, as when the vehicle was new.

The original factory advertised this as a permanent half-hour fix.  This is optimistic but so much easier than disassembling the differential as the Chevrolet dealers did 50 years ago.

 

Original Engines Must Breathe

Thursday, February 11th, 2010

Before the modern Positive Crankcase Ventilating System (PCV) most automotive engines breathed externally and removed their excess products of combustion into the atmosphere. It was a standard of the industry!

The lower end of the engine (below the pistons) had an attached draft tube that extended outside and below the block. It released blow-by from worn piston rings and other pollutants created from the crankshaft turning in hot motor oil.

The upper end of the overhead valve engine also must breathe. On early Chevrolet and GMC inline six cylinder engines, the venting is usually in the valve cover through factory slots. When an add-oil cap exists on this cover, it seals tight. It does no breathing.

On 1955-62 Chevrolet 235 six cylinders the valve cover slots were illuminated. It is assumed badly worn engines at high RPM leaked oil at these slots. The venting requirement was now moved to the oil cap. These redesigned caps have two features. They cover the add oil hole and vent the upper end of the engine. Their disadvantage is their internal filter can clog with oil vapors and dirt from a badly worn engine. This type venting cap must be kept clean!

The following photos show venting methods on early Chevrolet and GMC engines. Note the oil and breathing cap on the later six cylinder Chevrolet engines.

original engine 1

1937 through 1953 216 sealed oil cap (above)

original engine 2

216 valve cover vent slot (above)

original engine 3

1954 Chevrlot Vents (above)

original engine 4

1955-1962 non vented cover (above)

original engine 5

1955-1962 vented oil cap (above)

original engine 6

1963-1972… 230 and 250 with PVC system (above)

Sloppy Floor Shift Lever

Thursday, February 11th, 2010

sloppy floor shift lever

Problem: Slop in the shift pattern on 1937-47 Chevrolet 3 speed transmissions.

When shifting into 2nd gear finds your knuckles contacting the glove box door, repairs are needed

Repairs:

Chevrolet did not plan on these 3 speed transmissions to be in use over 50 years so repairs in this area were not often discussed by GM. You can fix it anyway!

Remove the flat plate with the shift lever from transmission by taking out the 4 retaining bolts. (Be sure to replace this plate with cloth or cardboard so no foreign object falls inside.) Take the shift tower from the flat plate top by removing four retaining bolts. The shift lever and its 2 1/4 inch tension spring can now be taken from the tower.

Inside the top of the tower is the worn brass bushing causing most of the shift lever slop. A replacement with tension spring can be obtained from Jim Carter’s Truck Parts and most of their full stocking dealers.

1937-1947 3 Speed Shift Repair

Shift Pin

Sorry, exchanging the brass bushing will not solve all the problem. The long horizontal pin, through the shift lever ball, needs to be replaced. The pin will probably be worn on each end and needs replacement.

Using a drill bit is a good option for a new pin. If a 1/4 inch drill bit easily moves into the shift lever ball, move up to the next size. (Maybe as much as 9/32 inch drill bit). Use it to drill the hole oversize, then use this same drill bit as the new pin. After drilling, remove the drill portion on the bit, and you have a nice hardened pin! Note: do not cut the drill bit until you know the exact length needed. Get a correct size by turning the shift tower upside down and measuring the distance between the two notches to the tower walls.

Timing Gear

Thursday, February 11th, 2010

About 10 years after the introduction of GMC’s new inline six cylinder engine in 1939, General Motors issued a ‘Product Service Bulletin’ in regards to a recommended improvement on the 228, 248, and 270. It appears the manufacturer discovered a weakness that shortened the life of the engine timing gears. This recommendation was made for enlarging the oil supply hole leading to the meeting point of the two gears. The attached dealer bulletin was issued January 31, 1949.

This is especially interesting considering over a million GMC trucks with these engines had been built prior to this. The number includes the five years of military large trucks that were used during WWII under very abusive off road conditions!

tming gear

Water Pump Modification

Thursday, February 11th, 2010

If you use a recently manufactured 216 water pump and combine it with the optional larger OEM radiator fan, a slight modification is necessary. The fan rivets will not clear the edge of the pulley hub. You must cut four notches in the hub for rivet clearance. Water pumps in the last five years appear to lack these notches.

Note: These larger fans, 18″ long, were optional on smaller trucks and always came on the 1 1/2 ton’s. It is the 15″ fan that will usually be on small trucks and passenger cars.

Comments courtesy of:
Bob Adler, Stephentown, NY.
bobadler@nycap.rr.com

water pump modification

Notice the four notches cut on the outer rim of the hub. (above)

water pump modification

Hub and Fan. (above)

Venting the Differential

Thursday, February 11th, 2010

Sometimes overlooked by mechanics and restorers is a small vent in the rear axle housing. This part is necessary to keep internal pressure equal to the outside atmosphere. Thus, as the internal temperature of the differential warms during use, any expanding heated air is vented and no pressure occurs. This saves wheel and pinion seals from leaking.

Check for this vent in your truck. From years of abuse many vent assemblies are missing. A sliding log chain wrapped around the axle housing for pulling is a way many vent assemblies were accidentally removed. The owner usually didn’t know the damage has been done or that a vent ever existed. Now, the small hole that once held the vent assembly is able to take in water. This will certainly cause long term damage to differential parts.

Differential Vent 1

Differential Vent 2

1946-1972 3/4 Ton and 1 Ton Ring and Pinion

Thursday, February 11th, 2010

One series of the famous “drop out” GM differentials was used between 1946 and 1972 on 3/4 and 1 tons. The complete assembly (often called a pumpkin) will interchange during these years with no alteration.

The highest gearing in this series is the 4.10 ratio and is found in most 1967-72 3/4 tons with automatic transmissions. Therefore, those “low gear blues” often associated with 3/4 and 1 tons during the late 1940’s and 1950’s can be greatly improved with no visible exterior changes. Originally these older trucks had a ratio of 4.57 in the 3/4 tons and 5.14 in the 1 tons.

Once a 4.10 pumpkin is located (usually in a local wrecking yard) it is a basic interchange requiring little more than new gaskets and gear grease. Your truck’s personality is now changed!

This interchange will fit perfectly if the “complete” pumpkin is used.  The 1963-1972 carrier is necessary and it will be part of this total assembly.  The change-over will not work if you only use the ring and pinion.

The only negative to this changeover is if you are hauling a ton of gravel up a mountain road with the original smaller six cylinder!! In this example a lower geared differential is best.

Early Gas Tank Danger

Thursday, February 11th, 2010

On most all early GM trucks their fuel line exited on the bottom of the tank. It was usually attached to a brass shut-off valve which threaded into the tank. In case of fuel pump or line repair, a person had to lay under the truck to turn the tank valve and stop fuel flow.

No doubt, this design resulted in many building fires as the trucks aged. By design, the tank is above the fuel pump. Thus, an un-noticed fuel drip or worse will continue until the tank is drained by gravity. What a dangerous mix in the many homes at that time with basement garages and nearby gas fired water heaters.

In 1954 the needed change occurred. The gas pick-up line now leaves the tank on the top but extends down to almost the bottom. In this way, the gasoline does not drain due to a line leak and sediment stays in the tank bottom.

For the perfectionist wanting his truck authentic, the original system does not have to be a fire hazard. Regularly check the short neoprene flex line between the tank and fuel pump. There is a limit on how long the non-metal flex fuel line can last.

For the non-perfectionist: Use a 1954 gas sending unit in the 1949-53 behind the seat gas tank. With a few line alterations fuel can no longer drip when parked. That is “peace of mind”.

early gas tank danger 1

1954 and newer (above)

early gas tank danger 2

1953 and older (above)

1937 – 1972 In Cab Gas Tank – Friend or Foe

Thursday, February 11th, 2010

What’s this bad rap some people give the GM pickups with in-cab gas tanks? For 35 years GM protected these tanks from collisions by double wall reinforced cab metal, doors, and seat frames. The 1937-46 pickups even secured the tank under the seat and surrounded it on three sides by the welded to floor heavy metal seat riser.

If you and your truck are ever involved in a collision so major that the gas tank begins leaking, then imagine what could be occurring if the tank was in most other places on the truck. Unless you have found a narrow tank that fits inside the frame rail and away from the drive shaft, you haven’t located a safer location than what GM used between 1937 and 1972.

For approximately 18 months, beginning with the 1947, Advance Design body style, GM placed their pickup gas tanks under the bed inside the frame rail. This location, while protected from side impacts, was very susceptible to damage from road debris. Leaks from being hit by rocks and stumps soon caused GM to again place the tanks in the cab. Possibly, a protective panel would have given the tank a shield but GM did not use this option. The tank went back in the cab.

In these older trucks you instantly smelled gasoline if the sending unit gasket or gas filler hose began to fail. Trucks with under the bed tanks usually must be parked and dripping before a person smells the vapors.

Important:  If you critique the early in-cab GM gas tanks, don’t forget what General Motors did to the truck series beginning in 1973. Can you believe? They secured the tank in their pickups to the outside of the frame rail under the bed. The only separation from a broadside accident is the single layered sheet metal bedside! It doesn’t take much of a side impact to flatten the tank with disastrous results.

Currently, the nervous owners of some earlier pickups move the tank out of the cab and place it under the bed behind the rear axle. This new tank position is definitely exposed to major damage from a heavy hit at the rear. An original in-cab tank is nicely protected from most of these rear and side impacts.

Remember, a Ford Pinto car being rear-ended in the 1970’s?  Their gas tank was behind the rear axle.  The resulting explosion and fire killed the occupants.  The Ford Motor Company paid dearly for that one.

Don’t make your truck more dangerous than it was originally!!

in cab gas tank 1

An in cab underseat gas tank as used between 1937 -1946…It lays inside a metal seat riser as well as being inside a heavy guage metal cab. (above)

in cab gas tank 2

The above photo wa taken of a 1952 Chevrolet 1/2 ton daily driven pickup. The owner was so concerned about the gas tank in the cab that he placed it under the bed behind the rear axle. The non metal tank is just waiting for a rear end hit at about 20 miles per hour. The original bumper will offer little protection and the contents of the tank will fly in all directions…Is this a moving bomb ready to explode?

Leather Gas Grommets

Thursday, February 11th, 2010

The United States and its allies suffered from major rubber shortages during World War II as the Japanese had control of most Indonesian rubber tree plantations. To survive without this material, much of the world was forced to settle on a limited supply of synthetic rubber of lesser quality. This material filled some needs but lacked the strength and durability of real rubber. Synthetic tires got half the mileage and this material had limited resistance with contact to solvents such as gasoline.

Leather Gas Grommet 1

This created immediate problems with the gas tank grommets on GM trucks. (This rubber ring seals the hole around the large gasoline add-pipe extending from the tank through the right side cab corner.) A synthetic rubber grommet was not practical in this location because of occasional gasoline spills during fill-ups.

Leather Gas Grommet3 3

A solution to the problem was using a proven material that was readily available in the U.S. It was leather! On the assembly line a punched leather disc was pressed over the gas add pipe and held in place against the body with a metal attaching ring. Four screw holes were punched in the body and ring at the factory for the screws. This leather grommet was not equal to the original rubber unit, but did hold its shape against the elements.

Leather Gas Grommet 2

Therefore, you can always identify a GM truck cab from this era because of the four punched holes beside the gas hole. The rubber gas grommets used before the war and after about mid 1946 will not totally cover these four small holes. Unless they are filled, by a body shop, the cab must remain the World War II type with the leather grommet.

This is not a bad thing.  The leather fits well and you have a great conversation item on your WWII truck!