The Stovebolt Site Forums The Shop Area Engine Shop i want more power !!!!!!

is there any way to up the hp in a stock 55 235 without major stuff? i wold really like a little more than 109 hp at 3500 rpm

That is a tricky question.

What are your goals for the truck? What can't you do now that you would like to?

ultimately it will be a tow truck, but right now the engine is in the process of being rebuilt (nothing fancy, just new paint, rings, bearings, you know, stuff that i can do at home) so i was wanting to make it a little more powerful if i could while it's tore down. i don't want a monstrously powerfully engine or i would get a newer v8, but i do want to get a little more power from the engine that i have.

P.S. the truck is a 55 2nd 4400 series


thanks in advance,

Indy

Maybe get a "848" head to bump the compression a bit.

Start with a 261, that's the simplest way to get more power out of an old 235.
Or get an auxiliary transmission for more gears. More gears is a good substitute for power when hauling a load... you won't be going fast though.

Grigg

materman, if you want more hp have your block bored and honed with a torque plate,put new pistons(cause you have too) and you will gain about 30 hp and your engine will last a long time if you do this,when you bore and hone your block this way your bores will be round under the torque of the head,and finish the bores with a 625 stone(sunnen) your rings will last, your engine will have more hp! when people bore and hone blocks without a plate they make the bores round, but when your torque your head on they go out of round and thats why people hone blocks with a rougher stone to make rings seat in.i have seen about .003 out of round when you dont do this and thats where the hp goes, you must have ring seal and valve seal to have a nice engine that last and runs like you want it to for a 6 cyl.hope this helps

Find a different cam, and you'll be able to gain easy power.

I agree with 46gmcpu

You can get a new cam of have yours reground (sp?) for more bottom end power.

You're not going to get 30 hp out of a re-bore.

Just about no one does this. Pricing/sourcing a torque plate for these engines will tell you why. IMO exhaust is the first place to start, then cam, carbs, etc.

Trucks need torque more than HP because gaining a lot of speed isn't worth a darn in the larger old chassis.

yes you will, i use to do R&D for jack clifford( before he died) and we did all the testing on my engine dyno and found out that if you can get your leak down to less than 5% instead of 18% you will make hp. i am not here to argue with anybody,i have torque plates for many engines and use them all the time, you can believe what you want to believe and thats fine with me,i just know performace engines and what it takes to make them run. have a nice day.

Do you have a torque plate for THESE engines? If so where did you get it? Have you measured bores with and without the torque plate mounted and how much variation did you find? Not doubting you just curious.

Torque plates work, and they're not that hard to build. I've used them for 30+ years on most of the engines I build. All it takes is a surface grinder, a drill press, and a boring bar. Getting that kind of horsepower improvement on a dyno run is total BS from nothing but a stress-honed cylinder, however.
An 18% leakdown rate on a cylinder balance test is an outrageous assumption. If an engine has more than 10% leakage it's time for a rebuild.
Jerry

yes i do have a plate for the 235-261 engines, i made them way back in 1990's when i have checked them after boring and honing them they are about .002-.003 thousands out of round,when you install your head on your engine they will come back to zero. if you put a torque wrench on the crank when you have installed the pistons and see how much lbs. it takes to turn over the engine without the head on it you will see about 38lbs to rotate it, then torque the head on it and check it and you will see it drop to about 32 lbs. thats what you want to see.holes are round under torque and great ring seal.you have to have ring seal first before you add any other stuff like cams and manifolds headers and such,and valve seal too.

all this chat about hi-perfing a 235 is a bit beside the point, mater wants "a little more power" for a tow truck, which really is torque, and what one could get for a reasonable price in a 235 wouldn't be noticeable pulling a 2nd vehicle .... either put up with the speeds your grand dad had or go V8, materman

and Curt, getting a torque plate for a 235 shouldn't be hard, and the price wouldn't be bad if you were in a position to rebuild enough engines

Bill

jerry, have you gotten any of these engines with a leak down under 3% and tested them on a dyno? again i am not trying argue with you or anybody else, i respect the machine shop guys, i just love doing these engines the best can be machined, i love early iron,and i love to hear what the sound like after i am done with them, i did do a lot of testing with all kinds of engines,and i do know that everybody has there opinion about engines, thats what makes it fun! thats why there are differant winners, faster cars on and off the track.

That one linked is for 250-292's and it appears the price for a 235/261 model is $868.45. It's probably safe to say no one now days will ever bore enough of these to get thier money back rendering this level of build cost prohibitive (except for those of us that have one).

i just wanted to make my engine a little more powerful if i could, not for speed, but to ensure that i don't tear up the engine trying to pull stuff that the truck can handle but not the engine. what i was really wanting to know are there little things that i can do to get a 1/2 horse here and there that will add up to more power without having to change the engine.

sorry if i confused anyone and caused an argument

Indy

i am sorry too mater, i just was trying to get you some more hp ,i thought you might be boring your engine and if you were you would gain some extra hp. i know now to say nothing here. too many pros on this site. good luck with your build.

If that's the concern I don't think it's a valid one.
Trying to get more power out of a given engine often adversely affects it's life expectancy. More power is more stress on the internal components, harder on the engine.

Getting what you have properly tuned and running well but still about stock is a good thing. Trying to make "extra" power is not necessarily a good idea if you want the engine to last.

As I said before gears are a weak engine's best friend when it comes to hard work. The truck will do most anything you ask of it if you take it easy and use low gears.

Grigg

I bet horsenaround in Ok could loan you a horse, that would give you one horse power more instead of 1/2, hook that baby up when you want to tow something

just funning with you,, check out this baby

you have to realize what your dealing with here. if it was a tow truck when new, it has all the power it needs to do the job. so operate it like it was 55.


grigg is right on here . i load my dump and have mountains to cross with it. i use the gears and its easy on my truck and on my pocket. if its a two speed rear then all you need sometimes is that half gear if not well then its a full gear but still easy on the motor. if you want to pull stuff in todays world then maybe a newer truck is in order. id be more concerned about stopping power than pulling power

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 Smithys.

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.

regards,
Leon

I b'lieve I've seen a book on "hot rodding" these old Stovebolt engines. For the price of around $20-$30 (used vs. new?)it might be worth the investment to read about what can really be done to achieve more HP. There HAS to have been ton's of previous discussions on this subject in the past?
Edit: Found it. Chevrolet Inline Six Cylindar Power Manual $29.95 at Classic parts. I'm sure other purveyors of parts like Am. classic might have the book as well. You can begin by making sure your manifolds line up properly and minimize any obstructions, etc. The comments on this book says it has blueprints, airflow charts etc. Sounds kind of high tech if you just want a Daily Driver? I remember pulling some mightly loads with my Dad's 3/4 t. 52, 4 spd.

there is no replacement for displacement.

that being said and if you want to stick with your existing 235, exhaust, cam, port clean up and carburation to get some power.

What Scott said x 2...!!!!!!

Chevrolet Inline Six Cylindar Power Manual $29.95 at Classic parts contains this much information about 216/235/261 engines: zero.

turbocharging

i had thought about a turbocharger but i didn't know if it would work

How would it not work?

as a point of fact, when I was ordering pistons from Ross, the fella said many people went with forced induction of some kind in old 6 cylinder engines as it isn't all that easy to get compression, and the heads flow horribly. If I had used the 235 crank in a 216 I could have gotten 8.5-1, but since I went with the 216 crank, the most they could give me was 7.6-1 which is still low enough for forced induction. I do know that 270 GMC rods will fit in the 216 and clear the cam, but I don't know about the 235,(longer stroke). You could give Gene Beck a call and he would know for certain, there is very little he hasn't done with these engines. He said the 235 crank in a 216 with the GMC rods will hit the cam. If you were to use these rods in a post 53ish 235 you would have to cut the big ends on each side to fit, as the journals are all different after 53. These crankshafts are quite stout, and the GMC rods appear to be nearly unbreakable, although heavy, which is fine if you turbocharge it, because you wouldn't need a lot of RPM to make power. Just some fodder for you to chew on in your quest for power. Not to mention the fella here some time ago adapting fuel injection from something or another to run on these engines. The only limit is how much do you want to spend. It also helps to have a friend with a whole pile of stainless tube bends and a tig welder.

rather than leo's inline 6 power manual you might check out california bill's how to hop up chevy and gmc sixes. not a lot of new info, but a good read and it pertains 100% to your engine.

I agree with hoggyrubber, old inline hop up books were written for your motor where Leo's books are next generation 250/292s.
I'd start with carburation, duals or single four barrel, then exhaust, HEI distrib or Pertronix. Check out Patrick's website look through his catalog, he's been at this Chevy six hop up biz for decades and runs a great shop, good people and stands behind his products. Best of luck
www.patricksantiquecars.com

thanks guys, all of your answers have given me some ideas of what to do.

thanks a lot,

Indy