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High Performance

Fenton vs Nicson Headers

Tuesday, February 25th, 2014

As the United States entered into the 1950’s, our country’s economic growth was breaking all records. The demand for merchandise from US factories had never been stronger.  For the first time most citizens had at least some disposable income that could be spent on non-essentials.

It was then that we began to see a certain segment of our population look toward the hobby of vehicle performance.  For the average citizen doing this, modifying a family car to produce additional horsepower, became a strong motivator.  Whether on city streets or a local town dirt track, competition racing for the average person became a new fun activity.

As a result, a totally new market emerged.  Speed equipment flat-head V-8 Fords and the inline Chevrolet and GMC six cylinder lead the pack.  Plymouth, Stude baker and Hudson were close behind.

This article relates to just one segment of this new performance trend:  the duel exhaust manifold of the inline six cylinder Chevrolet and GMC engines.

With more or a longer carburetor plus the additional increase in air to match extra fuel intake, a redesigned exhaust system was required for more speed.  This, the introduction of the dual exhaust system that removed the products of combustion much faster from the engine head. No exhaust back pressure under heavy acceleration.

The two most well-known high performance headers for these early GM six cylinder are Fenton for Chevrolet and Nicson for GMC (the two designs do not interchange properly between the two engines).  The attached photos show the enlarged diameter outlet and size of the Nicson’s due to the increased size 270 and 302 cubic inch GMC verses the Fenton’s on the 235 and 261 Chevrolet.

Both designs are currently being reproduced as very nice copies of those in the early 1950’s.  The outlet diameter of the gray Nicson’s are 2 5/8”.  The black Fenton’s are 2”.  Both type of headers are just right for the enthusiast that wants the unique six cylinder purr and a little extra in performance.

test test
test test
2″ Fenton Outlet         2 5/8″ Nicson Outlet

The King

Monday, February 8th, 2010
The King ATHS Logo
Its the annual convention of the American Truck Historical Society. This year, 2010, it is in Pleasanton, California. Over 700 trucks of all sizes and makes gather at the Alameda County Fairgrounds.In a far grassy corner is a  sub group of local early GMC owners. Most seem to be acquainted and use this show as a reason to renew old friendships. There are few “trailer queen” trucks in this group, just dependable daily drivers. Most owners know how to repair the occasional problems that are a part of driving a 50 year old truck.

A crowd begins to gather late afternoon on the second day of the convention in this GMC truck cluster. The attention is not so much on the 1958 GMC stepside 1/2 ton with its Pontiac V-8 plus three factory two barrel Rochester carbs and correct large air filter. The interest is on the contents of the bed.

Here, only heard of by most GMC enthusiasts, is a real inline 302 cubic inch six cylinder engine from the late 1950’s! It has all the aftermarket high performance options of 50 years ago. It sits on a special frame with no body panels obstructing the view. All is there to touch and feel.

The owner is John Christ of San Francisco, CA. He has built this 302 just like it would be for racing in the late 1950’s. John located a new engine about 5 years ago and since has been hunting GMC speed parts so he could build it just like the race track engines of 50 years ago.

This is the first time the 302 has been seen by the general public and almost never had John tried to make it start. He had planned for this moment at the ATHS convention for a long time.

As the crowd grew and watched, the battery beside the engine was connected. The small nearby temporary gas tank was attached to the fuel line. The foot start linkage was pressed by hand and engine began to turn. It does not start and fuel drips from line connections. Yes, John has a good size fire extinguisher.

A water pump drip is not repairable at the show but John climbs into the truck bed with the engine to stop fuel drips at joints and makes several other adjustments. He tries again.

The engine belches flames from the human skulls covering the Stromberg 97’s. Still no action. More adjustments are needed.Now the engine fires a few times. With no exhaust pipes this may get loud!!. John has a friend push the starter linkage while he turns more screws and then off it goes. It is running on all six and the sound is probably heard through most of the convention. Its almost like it is saying, “Where’s the race track?” Applause was heard from many in the crowd when they are not covering their ears. The King
A few of the items John has collected over the years makes this 302 just right:- Venolia Pistons, These very light weight aluminum racing pistons raise the compression ratio to 9.5 to 1. John had them custom made for this engine. Yes, premium fuel is a requirement.

– Howard intake manifold. Allows the use of five Stromberg 97 carburetors. The progressive linkage uses number 2 and 4 carbs when driving normally. Carb. 1, 3, and 5 are waiting to operate when speed is necessary. Fuel economy, are you kidding!

– The engine was totally balanced to prevent any vibration at higher RPM.

– The bee-hive oil filter beside the block cools the oil as much as it cleans it.

– A 40 year old Wayne valve cover and side plate are almost impossible to find. They  have never been reproduced for the GMC engine.

– The special high volume aluminum oil pan is a necessity when racing on the track.- Fenton headers. These lessen back pressure. Exhaust gases leave the engine much quicker under acceleration.

– A highly modified camshaft is a must! Getting more fuel and air into the combustion chamber adds to the available horse power.

A stock 302 GMC six cylinder with this equipment is why so many small town dirt tracks had to ban vehicles using truck engines in the 1950’s.

The local hobbyist racing a car engine couldn’t win a race against a built up 302. They wouldn’t spend the money to register if a high performance GMC was allowed. To keep the dirt track’s popularity, a sign was often posted “No Truck Engines” but secretly it meant no 302s.

The King
The King
John Christs’ future plans for his 302 is placing it in a recently purchased 1940 GMC pickup. It may be an easy drop-in but this little truck will have a real awakening when its time for performance! John can be contacted on the club website at www.oldgmctrucks.com under the name Big bad swing daddy.
The King The King The King

High Performance

Thursday, June 1st, 2000

This section is reserved for articles regarding high performance modifications to GM trucks.