Help me with a stroker debate

[85_SS_302_Coupe]

I'm not sure if this is Tech or not but i figured it's more tech than Talk so here goes. Feel free to move it if it's too Talkish.


I have a friend who has a pretty fast S-10 with a 355 in it. I have another friend with an '89 GT with a pretty rowdy 347. The S-10 friend says that it's not a fair race because a stroker crank changes everything...he says a stroker is always going to make more power even if everything else is the same...so i posed this question:

If 2 engines are built...one engine is a stock stroke 350ci engine and one is a 302ci based stroker displacing 350ci (lets just say you can get 350ci from a stock 302 block just for argument sake). Both engines have heads that are flow benched and flow the exact same cfm, and both engines have identical cam specs. Both have the same intakes that also flow the same cfm and both are running Holley 650 carbs and are jetting the same. Compression ratio is also the same for both engines. Essentially, they're the same engines except for the difference in stroke.

Which engine is going to make more power?

 

[bgjohnson]

Tis a good question. I would tend to think that since a stroker has more leverage on the crank that it's going to produce more torque, but only if the crank stroke is longer that the 350 stroke. It would be interesting to see comparables.

 

[85_SS_302_Coupe]

My thoughts are that, a stroker simply makes more cubic inches to catch up to where the 350 already is. I would expect them to make almost identical numbers if everything else is truely the same as far as the heads/cam/intake go.

 

[dcurtis]

A 347 is close enough to a 350 as far as cubes go, but the chevy already has 3.480 inches of stroke vs. the 3.4 of the stroker, so the chevy will still be bigger and have more stroke. Why not just compare a chevy bored to a 355 against a ford 351? or stroke them also and have two 408's?

 

[85_SS_302_Coupe]

Yeah, i just wanted to make a point specifically about a 302 based stroker compared to a Chevy 350. It seems to me that it's the same argument as a 351W vs. a 347....if compression ratio is the same then it's gonna come down to the H/C/I and then it just depends on which engine has the better combo.

My point is that a stroker engine isn't some kind of magical power making miracle. All a stroker setup does is "catch up" to where the 350 or 351 already is. The reason most 347s make more power than a stock or mild 350/351 is because they have higher compression.

 

[NIKwoaC]

There are too many generalizations in your buddy's statement about "stroker", which is nothing more than a term for an engine with a larger crank to produce more cubic inches. There are many other variables in engine (short block) geometry that determine performance. Consider also rod length (which influences rod/stroke ratio and therefore piston side loading, which translates into cylinder wall frictional forces) and bore diameter. While its true that big stroke cranks will produce more torque given the same combustion chamber characteristics, longer stroke engines also suffer from more friction on the cylinder walls because the piston has to travel further each revolution. This phenomenon only increases as engine speed increases, so for the most part, "stroker" engines may not perform as well at high rpm as what the same engine with a shorter stroke would have.

On the other hand, large bore engines have the advantage where expanding combustion gasses have more surface area to press against on the piston face, which also translates into more torque production, without the frictional losses.

This is only the tip of the iceberg for engine design. Sounds like your buddy with the S-10 is just making excuses!

 

[5spd GT]

Exactly, your buddy is just making excuses.

GM is 3.48"
Ford is 3.40"

The piston goes up .040" and down .040" more than the 347.

The R:S ratios are 1.638 for the GM and 1.563/1.588 for the Ford.

At those ratios, it is trivial and relatively meaningless to compare.

The GM block can "stroke" more, with the .800" taller deck height.

If anything, he has the advantage.

 

[Fast63]

Typical chevy talk. Our built 302's have been stacking up and surpassing built 350's for a long time now. When we throw a stroker crank in to actually even the playing field and come out way on top, they start crying.

 

[NIKwoaC]

Exactly, your buddy is just making excuses.

GM is 3.48"
Ford is 3.40"

The piston goes up .040" and down .040" more than the 347.

The R:S ratios are 1.638 for the GM and 1.563/1.588 for the Ford.

At those ratios, it is trivial and relatively meaningless to compare.

The GM block can "stroke" more, with the .800" taller deck height.

If anything, he has the advantage.

5spd GT, I couldn't remember who the guy was with the good link in his signature, but I knew you'd step in at some point! That link covers a lot of good info.

85_SS_302_Coupe, if you want some good technical backing to your argument, check out that link.

 

[SMOKEDYA]

yeah to me sounds like a typical cheby guy! so well us ford guys can play the game to! cheby guys say "whats all do to it" i say it's stock they look at me like i'm crazy, peace





john

 

[85_SS_302_Coupe]

Yeah we have a good friendly rivalry going...it's all fun though. I've drove his truck and it really does have some balls...he's had it 13.20s but i think it's got 12.70s in it if he would drive it harder.

 

[thumper460]

LOL... just a Chevy guy whining after getting his butt wiped with a SBF!! Those guys have been whining since the 351 came out... cubes are cubes the Chevy has the longer stroke/ longer rod.. blah blah...have fun with it!!lol

Just me ....

Thumper

 

[85_SS_302_Coupe]

Well, i've had my car 13.82 slipping the clutch and spinning the tires. It was my first time on drag radials and i was just getting the feel of launching the car when i ran that and i got shut down for not having a helmet. That day we were playing on the way home and i just barely pulled him from 50mph...and that was with my stock '87 heads and cam.

Now i've got my ported C90E's and a hand-me-down X303 and i'm ITCHING to get back to the track with him, but i blew my traction lock out last time so i need to rebuild it before i go back. The thing with him is he's afraid of breaking something...his truck is his baby..lol. I know it'll run deep in the 12s but he launches at 1800rpm on slicks. If he would drop the hammer at 5k i probably wouldn't stand a chance in the 1/4, but then again i have no idea what i'm gonna run now. People are telling me it's a 12.50 car now but you know how that goes..

 

[NIKwoaC]

Keep in mind your car just has better physics for racing than his truck does. Your weight distribution and transfer, aerodynamics, the whole nine yards -unless he has done a LOT to his truck- are better all around.

 

[backfocus]

Coupe, I know this is not answering your question, but just a reiteration about the S-10.

I raced a 85 S10 for 6 years with a 400 small block. Now I know it is more cubes than your comparison, but after much trial and error from me and my uncle, the best we could run that truck was 11.79 and 10.35 with gas both with 10.5 slicks. The problem with the S10 is that they are very difficult to hookup. We had a 4 link and tried many different combos, but after talking with a lot of people the only real way to go fast in them is too tub it and tube it.

But anyway what I am saying is the we were pretty maxed out for our combo, so if your friend with the 347 has a good combo it should be better than the 355. An yes all said above I completely agree with as far as stroke and displacement differences.

 

[85_SS_302_Coupe]

Yeah that's another thing...it's a long bed S10 so it's like a damn limo, and it sits like an old gasser and the suspension is stiff as hell. I keep telling him to lower it and put some drag shocks and springs on it and that would make a world of difference. He said he had it weighed and it came in just over 3000lbs with him in it (he's only like 130lbs) so he actually has me on weight...my car only weighs 2800lbs but i weigh 230...lol.

I think right now i've got him beat on top end, no doubt about it. The thing i'm not sure about is off the line. He's on slicks with a 3200 stall converter and a 3 speed (i think turbo 350 trans) with a reverse manual valve body, so his shifts are flawless. I'm gonna have to hook and out drive him if i'm gonna beat him off the line. I know he's making more torque than me so it's gonna be close. I'm already on the hunt to find a decent roller 351W to drop in it...then it'll be "fair"

It's funny, a while back when i was about to put my heads and cam on, he told me it wasn't fair because my cam (the X303) is way bigger than his .454/.480 lift cam and that it wouldn't be a fair race.....i said "yeah well what about that extra 53ci that you've got on me!?"