VCCA Home Forums TECHNICAL - 1945 AND EARLIER Chevrolet Speedsters hotrodding

Greetings
I've had a 26/27 chevy chassis sitting in the woods back of my house for several years now and I'd like to try to get it running with the idea of making a speedster, racer, or perhaps building a truck body. I understand these fours were popular as racers back in the day and would like to hop mine up somewhat. As I understand it, the 27 head is a good first step as it breathes better and the rockers are 1&1/2 to 1 lift as opposed to the 1 to 1 of the rest of the fours. Next, installing a slightly larger intake is desirable. Can anyone confirm the size?
Someone said the original carbs are slightly undersized, I guess for fuel efficiency, can the jets be drilled out slightly or is it best to switch to a downdraft. This is strictly a low budget project so I'm not interested in anything expensive. What are your thots?

http://www.jalopyjournal.com/forum/showthread.php?t=372127&highlight=chevy+speedster

The early Hotrodders used to use a 3 port Oldsmobile head on the Chevy four banger.

http://www.jalopyjournal.com/forum/showthread.php?t=516625

A 1928 head would probably also give you better fuel and exhaust flow as it has twin exhaust ports instead of the single exhaust port used up to 1927.

Dick Bertolucci, in Sacramento CA, uses a highly-modified '28 engine in his hill climbing racer and he wins most of the time. ;-) He is using the original '28 two-port head.

In the Forward of the '75 Years of Chevrolet' book, it states that early hot rodders used the Olds 3-port head, Nash rocker arms, hot magnetos, Jewett high-volume oil pumps and Durant connecting rods, all of which would bolt right in.

I used to have a '28 engine that was hopped up for racing back in the 1950's. It had the '23 Olds head, an updraft Winfield Model S carb (with matching cast aluminum intake manifold), and a cast iron Mallory two-point distributor.

I recently sold it to one of the VCCA speedster guys. You can reach them at speedsters14to28@yahoo.com

Cheers, Dean

Thanks for all the ideas. Being strictly low budget, I plan to use the 28 head and am toying with the magneto idea. I have two Carter carbs and are not sure what the difference is. I'm guessing the Winfields are hard to come by and expensive. I wonder how a Stromberg 97 downdraft would work?

Also, it seems that all of the period speedsters/ racers used Ford T front axles and transverse springs. Could this be because this setup allows the wheels to maintaining better contact with the road?

I was into the engine gasket business covering 1909 to 1950 from 1976 to 1990, as GASKET KING COMPANY LIMITED.

I DO NOT REMEMBER OLDSMOBILE OFFERING A 4 CYLINDER MOTOR IN THE 1923 ERA. whoops caps , sorry. In that era olds was offering V8 and straight six motors. A lot of their car and truck motors were made by MASON or NORTHWAY .

I wish I kept just one of those 1930--34 era gasket application books to reference now.

mike

Two port heads will give you more torque...Why he wins in hill climbs...Go with the 3 port, if your going for the speed factor...Two stroke exhaust pipes can be tuned for exceptional "climb", but 4 stroke exhaust can be tuned as well...Just don't expect the same "wow"...

I don't think those Olds heads are lying around on every street corner. If you find one, it will be expensive. Furthermore, I do not believe it is a bolt on and ride proposition.
Your '28 head will be fine for your application.
I have a '28 Chevy engine with an overhead camshaft. It was probably built by Robert Roof.

Mike

I have been told by a couple of speedster guys that the '28 heads out perform the 3-port Olds heads once you set up the engines correctly. Model A folks like the '28 heads to soup up their engines. So I am sure you can get a bunch more performance that a stock engine. I have heard that you need to use studs instead of bolts for the higher compression modifications.

Years ago I rescued a 1922? Chevrolet model FB that was driven into the woods and left. The model FB came out with the so called "cloverleaf" head. I installed it in my model H Chevrolet. It was a bolt on conversion. I sold the rest of the car. I have never seen one of these heads for sale.

It would be fun to bore this present motor out and put model A crank, rods, and pistons in it and build up a period racer. For now, I'm going to satisfy myself with the 28 head.I believe this to be a low mileage original motor.

I think there is a company on the west coast which does a balancing act on crankshafts which were not previously counterbalanced. they weld on laser cut counterweight plates and then rebalance the whole assembly. I don't know the name of the company thought , but it was mentioned here at chat a while ago. Some one may add the name.

Can someone explain what is meant by tuning the exhaust? As I understand it, the goal is to have the exhaust gasses pass from the motor with the least resistance and good flow. In making headers the size of the pipe is sized to allow the gasses to pass without turbulence. Is this called "tuning?"

Also, I understand back pressure is important?

That's what I was referring to, depending on the cam timing, etc...You should be able to find info like the proper length, etc... on the net...I recall seeing the formula for four strokes in an old "Cycle World" years ago...I used to build two stroke chambers years ago, before I gave up motorcycles...Man, would they scream...Many a ticket...

Tuning is an attempt to minimize the pulses in the exhaust system. When each cylinder exhausts the gasses come out slowly at first then peak when the exhaust valve is fully open and piston nearly at the top. Those pulses cause turbulence which reduces flow rate and the amount of fresh gas filling the cylinder for the next cycle. Pipe diameter, length, configuration, etc. effect the pulses.

That's why "back pressure" at a certain point is important...Otherwise your just dumping gas out the exhaust system...Another reason they run dual headers on these old 216's...I prefer a quite motor with a little more torque than a noisy exhaust and a little more top end...

I checked the HP of the chevy fours in the standard catalog of American cars today just for fun. The model FB, which came out with a longer stroke and the three port head, had 36 HP, while the 28, which only had the two port head, had 35 HP. There was a difference of 200 RPM in the rating of HP, but it is very interesting to note the difference in HP between the two motors. For all the hype surrounding the three port head, it would appear that the two port is better.

Some years ago there was a series of articles in the magazine titled "Speed and Sport." Does anybody know whether these articles were compiled anywhere?

Yes… they are all compiled in the hundreds of G&D's in my SOCR VCCA library! Stay tuned to the Homepage, and I believe they may be available in Flipbook form to VCCA members…

It would be awesome to see that series, and Ken Kauffman's series compiled into one giant flip book together...

I'd like to try to keep this thread running in the hope of hearing more of the tricks used to hop up the Chevy fours. I talked to a man at a recent flea market who had used a single port head on his A model. He used the car for hill climbing events. He said the intake valve was too small and needed to be enlarged to provide good flow but he couldn't remember how much larger. Does anybody have any idea?

I am in process of building a chev 4 based speedster and believe that the olds 3 port is superior to the 28 head so long as you increase valve lift. The olds head rockers are 1:1 while the 28 rockers are 1:1.5 Alternatively you can use flat seat valves.

Re the use of ford transverse springs - I think it was primarily a weight issue. The likes of Gerber discarded the chev short spring chassis for a T chassis for weight reduction. The T chassis is made of superior steel but is probably half the weight of the chev.

Good advice bopnz. I wondered about the T chassis. I'm guessing the transverse springs would improve traction on the front and rear ends on a banked circle track as well. Are you going to use a T frame or the Chevy? It is almost impossible to build a correct speedster/racer without using the T chassis. Have you seen the pictures of the Australian racers posted here?

Also, the info on the two heads is good info. I didn't realize the FB head or cloverleaf as some call it had 1 to 1 rockers. Somebody said that 6 cylinder rockers were also 1.5 to 1 and would bolt up to the 4's. Can anybody confirm this?

One more thing, we've all heard of the virtues of the Winfield carbs, I have a guy who is recommending a Stromberg OX-2. He says it is a good carb and comparable to the Winfield. I am wondering about just switching to a six cylinder chevy carb? Also, it seems to me, a stromberg 97 downdraft might work good. The 97's were great on the Ford flatheads.

I was told by an old hot rodder (Carl Schmid) that the OLDS 3-port head that I used to own, had 1929 rocker arms on it. These rocker arms where bent sideways a little to make the the connection from the push rods to the valves.

Cheers, Dean

Re Carbs - I think Ford guys prefer Stromberg 81's on Model A's. I am using a single winfield S downdraft but may go to SU's depending on how its runs.
Re - rockers - you need to move the fulcrum so not simply a case of changing to later rockers. There is a bit of engineering involved. You can use flat valves to get better opening. Back in the day Nash rockers were used.
I am using a T chassis but guys in the 20s often made 3 springers by replacing the back semis on the chev chassis with a model T cross member and spring. This removes quite a bit of weight as you can imagine.
Fitting a chev 4 plus running gear into the T chassis is not very hard at all.