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1934-46 Tech Talk

1934 – 1946 Chevy and GMC Technical Article Listings

Wednesday, March 28th, 2018

 

Accessories

Bed

Brake Cables, Drum Wear, System Changes

Cabs, Heaters, Dash Panels and More

Door Handles, Panels, More

Electrical, Horns, Ignitions, 6 Volt Starting

Frame and Chassis

Gas Tanks

Grilles

Interiors

Lighting, Switches, Bulbs

Mechanical, Engines, Timing Gear, More

Military

Misc., Headers, Long Beds, More

Paint Colors, More

Sheet Metal, Fenders, More

Side Mount Spares

Speedometer and Gauges

Speedometers to Go…

Split Rims

Suburban/Panel Truck

Suspension, Shocks, Axle, More

Trim, Hub Caps, More

Upholstery, Seat Covers, More

Wheels, More

Windows, More

Wipers

The 20 Year Chevrolet Horn

Wednesday, April 16th, 2014


This new horn design was introduced in 1934. It is attached direct to the 207 six cylinder engine and was so successful there was almost no changes through 1952.
As shown in these photos this 1934-36 horn was attached to a flat foot that secured it to the center of the intake manifold. A long nose directs the sound to the area very close to the radiator cooling fan.
A slight change to the exterior appearance occurred with the new 1937 216 cubic inch engine. Possibly to keep it away from the high temperatures of the exhaust manifold, the horn was relocated. It now was attached to the forward leg of the intake away from engine heat.
The “bell” part of the horn was shortened to keep it the same distance from the fan. There, it remained on cars and trucks with the 216 engine through late 1952.
It was so well designed it rarely required attention. A single screw secures the rear half circle cover. When removed the inner workings are exposed for an occasional tone adjustment.
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1934 – 36
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1937 – 52

Short Shaft Water Pump Discussion

Monday, March 17th, 2014


The revised Chevrolet 235 and 261 high pressure inline six cylinder engine (1955 through 1962) was given a much better cooling system than prior years. This was due to a big change in the water pump and how it attached the front of the engine block.
The prior 216 and early 235 design pulled coolant out of the engine block through two quarter size holes, into an exterior pump, then forced it through the lower radiator hose and back into the engine block. This system worked well for millions of Chevrolet cars and trucks for at least 16 years.
One of the difficulties began to develop as these vehicles became older and were exposed to faster speeds of more modern roads and radiator coolant water contained a high calcium content.
Calcium started to slowly accumulate inside the block but even more in the radiator cooling tubes. The coolant temperature would rise in the block due to slower water circulation.
This was first noticed in the low geared 1 ½ and 2 tons, even with their extra row of radiator cooling tubes. Local radiator shops would remove the top radiator tank and “rod out” the cooling tubes to restore most of the original radiators ability.
With the introduction of 2 new Chevy six cylinder in 1955, General Motors made a change in the water pump that would at least postpone this over-heating problem for many more years than the earlier engines.
Now, the water pump propeller actually was inside a 4” hole in the front of the block. It could move a higher volume of coolant through the block. Chevrolet cars and trucks could now be used so many more miles before this rodding of the tubes was necessary.
With General Motors wisdom, they designed their new high pressure 235 and 261 engine to easily fit in the place of a failing earlier 216 engine. The main problem with this engine exchange was the longer length of the new water pump shaft.
Local mechanics would then either cut some metal from the upper and lower air dam to move this radiator forward a few inches or shorten the pump shaft to provide radiator clearance for the fan on a new 7” pulley.

The word spread quickly that the shaft could be cut and the 4” diameter pulley from a 1953-1954 would press in the proper position. (Most shops could find one of these pulleys on a nearby used engine)
All fit well but the rotating RPM speed of this small 4” pulley turned the fan and pump 20% faster at the same vehicle speed. Because of the low engine gearing of the larger 1 ½ – 2 ton trucks we have heard owners feel their water pump experienced “cavitation” (the fan is turning so fast water flow will almost come to a stop). It may not boil the coolant but it just might! At slower road speeds the water temperature returns close to normal. A small 18” fan from an early 216 donor engine was also required to prevent contacting the lower radiator tank.

NOW enters another modified water pump that has a much flatter 7” diameter pulley. This lowers the fan speed to the correct RPM that GM intended to be used on ½ ton up to the 2 tons. It was a one size fits all!
It is the other short shaft pump design! You can easily install this modified 235 and 261 engine in the 1953 and older truck (and cars). It is strongly recommended that you use this pulley pump for Chevy trucks rated over ½ tons!
It requires the correct wider four blade 235 fan, however the blades must be bent slightly forward to miss the lower radiator tank.

Therefore, if you want to operate your 235 and 261 engines water pump at a slower speed as GM intended, the 7 inch pulley design is the way to proceed. It will cool ¾ to 2 tons with lower differential gearing at high speeds with no boiling, just as the vehicles were designed. Yes, Jim Carter Truck Parts has the new updated pump assemblies available at a price of $159.00 (a used original wide blade fan is by another order).
A small 4 inch diameter pulley water pump have been placed on a 235 or 261 engine since they were first introduced. They usually work well with vehicles with clean radiators on cars and ½ ton light vehicles that have been given a higher speed differential. Not recommended for larger trucks as water temperature will raise at higher speeds! We have these that operate well (without add-on air conditioning) at our company at $130.00.
As the owner of Jim Carters Truck Parts, I can assure you we have sold over 500 short shaft water pumps with 4 inch pulleys in the last 10 years. Return rate is about 4%. I suspect it is rarely due to an inefficient pump but rather the new customer not aware of the difference between a 216 and later 235 six cylinder. Maybe a few were using them on a low differential ratio ¾ to 2 ton truck.
Does the 4 inch pulley cool as well as the 7 inch design? Probably not on larger trucks! In some situations, if your radiator has calcium build-up, the coolant flow can be so restricted, your temperature gauge will show an increase at highway speeds. The 4 inch pulley turns the water pump much faster than GM intended!
With the low differential gearing (as in the ¾ ton to a 2 ton) plus driving higher speeds, the increase engine RPM will definitely cause temperature increase. It can go so far at very high speeds causing the water to cavitate and the coolant circulation will almost come to a stop! It may not boil the coolant but it just might!

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4 inch pulley

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7 inch pulley

1940-46 Map Lights, All Trucks Had Them!

Wednesday, December 11th, 2013

 Within 10 to 15 years the delicate factory three position light switch under dash usually broke.  Replacing this switch on a working truck in the 1940’s was usually not an option.  Now almost 70 years later few owners of these early GM trucks even know the light switch existed.  In most cases the little single filament light bulb and socket still remains hidden behind the middle of the dash panel.  A horizontal slot in the dash once allowed light to be emitted into the cab area.  Just right for reading a map!

NOW, they are once again available.   Various tooling was made so all parts of the switch would fit together.  One side illuminates the dash cluster, one side is for the map light and the middle position is off. Just like GM did it!  All 1940-46 Chevrolet and GMC trucks have the factory under dash holes for installation.  Contact Jim Carters Truck Parts at 1-800-842-1913 or check on line at www.oldchevytrucks.com. Mention item # EL157.  Price $29.50

 

Accessory GM Reflector

Thursday, October 24th, 2013

To add better night visibility to all trucks, Suburbans and panel trucks, General Motors offered a 4 inch diameter reflector as a dealer installed accessory.   With the single small factory taillight, seeing of these vehicles on the road could be difficult especially if their one bulb burned out.  To help correct this problem GM offered a larger reflector that could be attached to the rear license plate bracket.  It greatly improved visibility to others at the rear during night driving.

This was a time when town street lights were limited.  Of course, on the open road these were no lighting along the highways!  This simple GM reflector was offered by the dealers to prevent rear end accidents.  The customer could buy this dealer accessory from about 1940 through 1953. One of the attached photos is taken from a 1949 Chevrolet Truck Data Book. The 4 inch lens is a Stimsonite # 24 and the metal Guide ring has a stamping of X-19.

Jim Winters of Rochester, Minnesota has both a restored 1946 panel truck and ½ ton pickup.  He found these reflectors for both his vehicles at local swap meets.  Few people recognize what these reflectors were used for.   Jim found his in a box of miscellaneous unmarked parts.

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1939-46 Panel Truck Rear Windows

Friday, October 11th, 2013

General Motors made it very simple to replace the two small windows in the rear doors of these early panel trucks.  It made it especially fast on the factory assembly line.

Simply place the rubber seal (now available from full stocking early GM Truck Dealers) around the pre-cut glass.  Press into the inside window opening. Three special clips secure it in place. It could not be easier! See Photos.

Oops, one big problem. If you don’t have the special clips, Good Luck!
This 1941 Chevrolet Panel Truck owned & totally restored by Jim Winters, Rochester, Minnesota.


Outside of door

Inside of Door

1946 Chevrolet 2 Ton with Thornton Drive

Monday, July 8th, 2013


Owner: Howard Jones

During the recent annual convention of the American Truck Historical Society in Yakama, Washington we noticed that among the 813 registered trucks there was a Chevrolet that may be the only survivor of this design.

The vehicle was a 1946 Chevrolet 2 ton with a Thornton dual rear drive. How unusual! This non-General Motors accessory allowed all four rear wheels to give pulling power. There is no disconnecting two wheels when on a highway!

This was featured in the 1946 “Chevrolet Silver Book” which has pages of accessories that were not dealer or manufacturer’s products. Sorry, the pages from this book are so small in the Thornton photos. A few other photos taken at the convention are also included.

The owner had made an opening in the new bed so there was a good view of the differential by the general public.

This particular Chevy with Thornton drive is said to have carried a D-6 Caterpillar dozer off road in the 1950’s to clear the right of ways for local power lines. It also had a large water tank mounted to the front of the bed.

The odometer reads 15,775 miles. It will reach a speed of 40mph on level ground.

More details on the Thornton Drive and its current owner will be with our August 2013 Feature Truck of the Month.

A Real 4 X 4!

–>

1939-46 3/4 Ton Rear Bumper Braces

Wednesday, June 12th, 2013


Yes, they are different than 1/2 ton!  Though the “C” shaped brace that attaches to the bumper is like the 1/2 ton, the brace from there to the frame is much different.  A curved single heavy brace connects to the frame rail in place of the pair on the 1/2 ton.  Of course, all are of spring steel to prevent distortions when occasionally hit in daily use.

Before Dual Filament Headlights

Thursday, April 11th, 2013


During the early years of automotive history, the invention of the dual filament light bulb had not emerged.  Therefore, there was no high and low beam headlight bulb on cars and trucks.  Only one beam existed for night driving.

This created a problem with the headlight beam from an on-coming vehicle on the narrow roads in town and country driving.  It was not until the late 1920’s that the two filament headlight bulbs came from the factory on new vehicles.

The attached photos show a great example of American Ingenuity sold in some vehicle parts stores during the 1920’s.  It is an electrical rheostat that allowed the driver to lessen the amount of light from the headlight.  This accessory was mounted on the steering column.  By moving the long lever with a finger, the driver could regulate bulb lighting.  How ingenious!  This very attractive assembly was recently found in an old trunk.   The unit is nickel plated as chrome was not yet available during these early years.  It is a very high quality part.

The price was $7.50, very expensive considering most workers made less than $1.00 per hour.   The sales company is shown to be the Universal Distributing Company of Tulsa, Oklahoma.

No doubt, the sales were limited due to the price but also because of a human trait.  Yes, the vehicle owner could lessen his light on the road but chances are good, the on-coming vehicle did not have one of these inventions.  The person that had spent the money on this accessory still received just as much light in his eyes from on-coming vehicles while he suddenly had less lighting from his vehicle!

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.

Installing an Updated Duel Chambered Master Cylinder

Thursday, August 16th, 2012

Warning:  When installing an updated duel chambered master cylinder under the floor of an older GM truck, a brake line modification may be necessary.

It is not acceptable to allow the modified brake line to touch or be very close to the exhaust pipe.  During long trips, the exhaust heat can cause a rise in the brake fluid temperature to near boiling level.  Modern master cylinders do not have a vented cap to release line pressure so fluid will be forced out through wheel cylinders.  The early single chambered caps are vented to prevent this.

Check your brake lines on non-original trucks.  Do not allow a safer system to leave you without brakes.

1941 – 1946 Chevy / GMC Steering Wheel

Wednesday, December 21st, 2011


We have received so many requests over the years for the 1940 – 1946 Chevrolet / GMC steering wheels, we decided to make an exact replica. They are now finished and soon to be shipped from the factory. These steering wheels are complete with correct metal internal parts, non-metal exterior with ridges, and even the two proper colors available 65 years ago.

The result is a show quality copy of the GM original steering wheels. We already have complete the horn parts that fit in the steering wheel hubs.

To go directly to the steering wheel on our website, please click the buy parts now button.

Early Dash Gauges

Thursday, February 11th, 2010

Gauges in Chevrolet truck dash panels during the mid through late 1930’s are very similar and are spaced, from each other, almost the same. Even their smaller chrome gauge rings interchange. The 1934-35 gauges are in the middle of the dash and there is no glove box. The 1936-39 instruments are centered above the steering column with the glove box on the right side.

Early Dash 1

When restoring these rare gauges, waterless decals are now available to help make them look like new. They are available from Jim Carter’s Classic Truck Parts as well as a few other full stocking dealers.

Early Dash 2

1936-1939 Glove Box Lock

Thursday, February 11th, 2010

This early glove box lock assembly has a weak point that makes it difficult to find complete. Its die-cast vertical pointer is held in place by a small steel tension spring. After the truck sets outside abandoned several years the spring rusts, breaks, or otherwise looses its tension. This allows the pointer to fall out and the glove box lid will no longer stay closed.

Most all locks you find will be without their pointer. The enclosed photos show a complete lock with pointer as it must be to operate.

Glove Box Lock 1

These locks do not have the ‘push button’ mechanism as the later design.  A small spring button attached to the dash moves. With this style, you pull on the key knob in the door when it is unlocked to overcome this spring button.  You don’t have to use the key to open the door.  Just pull the lock knob.  To lock the glove box door, just turn the key and the pointer moves forward.  The door is now locked.

During the beginning months of this 1936-39 lock, a double sided key blank was used. This blank has not been available for many years. If you need the early style your local locksmith may not be able to provide a key! (And the search begins.)

  • Painting your glove box door? You will need to remove this lock assembly. Here’s how: Turn the key to the right while pulling up on the pointer. You may have to jiggle it as you pull. Out it comes including the small tension spring! Now the large retaining nut can be loosened and the remainder of the assembly can be removed.
  • Lock removing tip from Scott Phaneuf, Hatfield, MA.

Glove Box Lock 2

Glove Box Lock 3

Hammered Interior Paint, 1940-46

Thursday, February 11th, 2010

During 1940-46 the Chevrolet GMC trucks came standard with an unusual interior paint. It added a little extra appearance with minimum extra expense. This has been referred to as “Hammered Paint”. While drying this paint develops a fish eye appearance. This helped make up just a small amount for no cloth door panels or related extras found on GM cars. After all, trucks were for work.

On these years of GM trucks all removable interior sheet metal is given this hammered paint. It includes the dash, windshield posts, door panels, rear cab sheet metal, Etc. The specialty paint is available from Jim Carters Classic Truck Parts and a few other full stocking dealers as follows using our part numbers:  Chevrolet PT106  –  GMC PT133.

Here is the story on our 1940-46 interior paint. Thought I should share some of the facts of how it happened. About 25 years ago I purchased a NOS glove box door. If I was ever going to match the color, this is what I would need. (Possibly just setting in a dark store room for 50 years might cause a chemical change to the paint pigment. Don’t know) No other parts supplier, then or now, wanted any part of making hammered paint. No takers when we ask anyone to do it. Finally, the Randolph Paint Co. in New Jersey almost 25 years ago, offered to try to produce it in quarts with very high quantities.

The product they created seemed to be very close. Maybe within 10% of the NOS glove box lid. Our relationship lasted well until 2014 when they either went out of business or just no longer had an interest. The paint hunt was on again!

By then we discovered a national brand starting to produce hammered paint in quarts in several colors. One they called bronze and we used it! It later was found to have a little too much silver but it was all there was. We marketed many quarts for several years, however some perfectionists made negative comments about the extra silver in the hammered texture.

One last attempt would be made to be correct: Then a new idea emerged. A quart was taken to a local auto body paint store with a slight color change in mind. The employees had not heard of hammered paint and wanted no part of the project. Fortunately, the owner was in and we had bought from him for 30 years. So at our cost, he would give it a try with an additive.

Wow, with added tints, we met with what we felt was a success. The NOS glove box door was sold almost 20 years ago however, the color seemed very close. No perfect examples we can trust remain that we have found.

So this is what we market today. Much better than the Randolph Paint Co. days. Is it perfect? Probably not. Seventy year old NOS parts could have faded slightly even in a box. It is all we have but we think it is near show quality. We have made quantities in quarts and now spray cans. It only receives compliments from our customers! It is just “slightly” darker than the two photos of the old Randolph Paint shown in this article.

NOTE: It appears GMC wanted to be just a little different on their interior color. We finally created this tint in a separate part#. See Above.

hammered 1

hammered 2

hammered 3