The Stovebolt Site Forums The Shop Area Engine Shop Is a peppy 235 possible?

What can I change to give my 235 a little more performance?

I just got my first project here recently and my first big expense is getting the 235 machined and rebuilt. I've been told that these old 235's were not made for performance, but I've read of people putting things like a larger lobe cam, dual and tri-power carbs set ups on there engines.

Do these performance mods do much for these straight 6's? If so, what else would you have to do to accommodate these mods?

Now I know this a very broad question, cause there are a ton of things you can do to a motor to improve performance, but is it worth it on these 235's? Thanks for your input.

it helps I suppose, but being "worth it" is a relative statement. I spent and ungodly amount of money on a 216, and an insane amount of money on a wayne 12 port, and hope to get 175 horsepower. It is all about what you want.

Back in the day these motors were hot rodded extensively. The first Corvette's came with a 235. There is definitely more power to be had from a stock 235. Check out some of the books on the subject or do a search here and you'll find lots of useful information.

Output potential is also dependent on what year 235 you are starting out with?

John

Carlos (Los59),

If you have a 1959 235 you have the best head for high compression. 150hp was supposedly produced by the 54-55 Corvette engine. Your 1959 head produces a higher compression ratio than the Corvette 235 head.

A higher lift cam might help, but I think (perhaps incorrectly) the 261 cam (used in the 235 Corvette engines) might have been used in later 235 engines? Higher lift cams are available - others who have used them might have opinions about them.

Going to multiple carburetors is cool and might get more power. Getting an properly matched adjustable jet carburetor be just as good and be easier to adjust/maintain (like a Zenith carb from a GMC 248 or 270 engine)?

im building a 235 for my 46 1/2 ton truck, i've had it bored .30 over, worked the 848 head with bigger valves,and im putting in a 3/4 cam with a high lift and a clifford 4 barrel intake with a big 4 barrel carb, and im making my own header for it that will run thru the fender well and down and out along the running board, with the t-5 i have in it and ford 9 in rear,i should be able to get a lot of hp out of it, stay tuned.....curious to get it dynoed and find out what it will pump out

I know of a 235 in a 41 Chevy that was meticulously machined and put together by a reputable speed shop. I don't know all of the particulars, but I will tell you what I do know. Bored .060 over, 848 head milled, resulting in 8.5 to 1 compression, cam of unknown make, fenton headers, clifford intake with a small Holley 4 barrel, I'm sure the head was massaged some. The engine made 150 horsepower on an engine dyno. I am sure that if he had not been good friends with the speed shop owner it would have cost him lots. There are always trade offs when building any engine. Dual carbs on these small displacement inline sixes will improve fuel distribution somewhat. However you are going to give up some low end torque to gain horsepower in the upper rpm range with dual carbs, not to mention a much bigger hassle to tune. Horsepower ratings in the 50's were figured differently than they are today (a little more optimistic back then). I would like to see a 50's stock Corvette 235 on one of todays engine dynos to see what kind of power it would actually make. If you can assemble the engine yourself, and know how to double check ALL of the machine work (includes the necessity of having all the tools) and have some tuning ability, be able to check piston to valve clearance, a mild cam, a little more compression, split manifold or fenton headers, a little clean up of the ports in the head would give you a broader torque curve. That would be what I would want for a street 235. Bottom line is how thick is your wallet, and what are your abilities. Good luck!

Answer to your question is YES. I have a 58 Chev 235, 848 head, 261 cam, Fenton split exhaust and stock Rochester 1 barrel carb. Purrs like a kitten at idle but goes like a cat with turpentine on its butte when I put my foot into the carb.I have 2.65x75R16 tires and a 4.10 Eaton rear gear set. I have seen 70 mph , GPS speed and still had room on the pedal.

Bunch of good insight thanks guys. So what I've gathered is its possible to gain a little performance depending on your ability and knowledge of how to make these different modifications work together. So I still have a lot learning to do.

So I think I will just keep this first engine stock for now until I have a better understanding of what I'm doing. Since this is my first project and I'm a noob, just taking this apart and maybe getting a manual to reassemble will be a good learning experience. I'm also in school so I'm hoping once I take my engines class I'll have a better understanding of what I can do. Until then its just research, research and more research.

Wallet isn't that thick so I think these responses have changed my mind to hold off and learn for myself. Thanks a lot guys ya'll have been a really big help.

With a thin wallet which it happens to me a lot too its always the time and money thing. The 235 is not cheap but fun to do. Lots of room and no smog. I would not trade it for the SBC or BBC in my 56 3100. If my wallet was thick I would build the "Cadillac 261". For now taken advice from guys here I am running a 1956 Chevy 235 bored .030 over with 848 head with hardened seats, 261 stock cam, Fenton split exhaust, Fenton 2x1 intake manifold, dual Carter Weber Progressive 2 bbl. with electric choke, mini H.E.I. and a t-5 transmission. Slow process but love the stovebolts. Not sure what kind of ponies I am running but enjoy the the 6 cyl. You have a good attitude learning it is part of the fun. Good Luck with it

thanks a lot.

I achieved some modest gains with better exhaust on my 55.1 235.
It's stock except for a Corvette exhaust manifold and dual exhaust with 22 inch Smithy's.
dyno results

I picked up 11 lb-ft of torque at 2000 RPM, about a 6% gain,
and 6 HP at 3000 RPM, about a 7% gain.
Measured at the wheels.
Cost was about $700 IIRC, since I built the front exhaust pipes myself.

It's nothing like the Cummins turbo diesel brute in my 04 Dodge, but I consider the 235 pepppy enough to be fun to drive.

regards,
Leon

Sweet with his 261 and me with my 235 had a little drag race up on the highway recently, got them up to 85 mph before we shut them down.

I've been at 90 in my 261 bored .060 (making about 270ci) with AA-1 2-barrel Holley and Fenton dual-exhaust headers and 3.55 rear and 31.5 radial tires - and a calibrated speedometer. The road was straight and clear AND I check my paints and found no wet spots. This was a one-time deal.

Of course, my brakes are in excellent condition, as are my tires, as are ALL my original-style front-end and suspension parts.

nice 90 mph. I wanted the 261 but since I have the original motor I wanted to keep that old 235. I am envious on the speed. Hopped up or not its all fun. I hope I am not too chicken to take mine 70 mph with the old time suspension.

Hey Tiny Jaime,
If your suspension(steering AND brakes) are in good shape 70mph is no problem. I do it all the time on I-10. You just have to hold on tight. But remember, these trucks ( mine is a 59 tf)are not designed to handle like a modern vehicle, they were made to work slowly. Drive slowly, be careful and know that you can if you need to go a little faster, safely.

My 51 Styline Deluxe powerglide is stock with the exception of having removed the cast iron pistons, and replacing them with aluminim pistons. I can't help myself every time I drive that car I run it up to 70 mph, and it has seen a top speed of 85 so far. There is a little left too!

Now that I bumped up the timing on the 57 235 in my 37 it runs good for just a stock motor,I kept bumping back the timing trying to find the rattle in the motor and forgot to bump it back up after the rattle was found. The flywheel has no ball so its been timing by ear since it was installed and has 3.55 gears and a t-5.

302's are out there if you want to stay I6. Making it fit into a truck made for a 235 might by interesting.

What would a 302 bored 30 or 60 over get you?? Has to be close to 350cuin.

The 235s are nice... but I like the 270s like whats in my 2.5 ton.

302 GMC bored .030 makes 306 cubic inches, if bored .060 makes 311 cubic inches.