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Your right Cab, Coomer mispoke, that will happen.

To the original question, in most cases, with the same CI, The bigger bore is the way to go.

Technically, with the same PSI combustion pressure, both equal CI engines would produce the same output if the A/F intake charge would remain the same.

But typically the heads are always shrouded by the bores with the production motors that we use for racing. Therefore, the bigger bore will always rule VS longer stroke Same CI.

It will have a lessor effect on a smaller HP motor say 500 HP and a much larger effect on say a 900 HP motor.

Dogday, and others good posts.

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i have to agree.
aside from that, in the real world nobody would build one of each with identical parts anyway, would they?

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For racing I would go with bore... but for the street
I would go stroke due to the rpm factor and the leverage

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... in the real world nobody would build one of each with identical parts anyway, would they?

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Does a Chevy-oriented magazine count? IIRC, I may still have copy of one where they actually built two versions of the same SBC engine, one as a 383 (3.75" stroke + stock bore) and the other as a 377 (stock stroke + big bore) to see the outcome. (Even the same cam was used, which IMO means if it was "right" for one of them, then it was also "wrong" for the other. )

The two engines performed pretty much as people would expect w/ the 383 making more torque and the 377 pulling a little more peak HP. From what I recall, the differences weren't major, yet fairly predictable.

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I turn a 4.5 stroke 8K with a set of 440-1's. I know a 4.15 stroke will go that too. The 4.5 stoke has way way more cycles per minute, which wears out parts though.
I know this to be true, despite what the text book racers may think.

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Bob, are you sure that what you wrote is what you meant? RPM are RPM regardless of stroke, 5000 RPM is 5000 RPM with two inch stroke or a four inch stroke The ring and piston travel, distance traveled, is more on a long stroke motor than a short stroke motor 5000 RPM on a two inch stroke motor equals 10,000 inches per minute, the four inch stroke motor rings will travel 20,000 inches in the same minute Not trying to start or make a war, just trying to make sure what we are discussing is accurate and understood the same by all readers

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Yea thanks for clarifying, I got it backwards guys... I get into a hurry and dont proof read none..
Just to clarify my point.
Stroke or Bore size has little effect on peak rpm, compared to the impact of head volume. People do NOT select bore size in reguards either...
Most go with the largest bore size possible cause we know it helps. I think Bore Vs stroke, bore is the clear winner. We usually start with 3.75" of stroke as a baseline. Stroker cranks are had now it just doesnt cost hardly any more to build a bigger engine, so...
I think the engine I outlined before is relevant, there is lots of guys with flat tappet cams and Indy heads, lots and lots more than larger- big bore, long stroke engines.
It falls back on the availability and cost of a aftermarket block. 90% of Mopar bracket racers are still using stock blocks. So figure bore size range from 4.32-4.375.. Which leaves stroke to increase cubic inches. I think the 4.25 stroke is "Best" along with the largest bore size possible.
This coming from a guy who's last two engines where 4.5 stroke, large bore aftermarket block engines. So Im not exactly speaking out of my butt here. These engines arent dyno queens, or test beds for bolt on parts....
matter of fact they were NOT dyno tested at all. Only numbers that matter to me is the ones they generate shortly after they are first fired at the local track.
The engine Im slowly slapping together will be the largest bore possible with a aftermarket block, and a 4.25 bottom end..
I believe it to be more effective than my previous setups, when you look at HP per cubes.

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... in the real world nobody would build one of each with identical parts anyway, would they?

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Of coarse not, thats the point... This is the type of engine that 90% of the racers are building though, so it matters plenty...
.

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Does a Chevy-oriented magazine count? IIRC, I may still have copy of one where they actually built two versions of the same SBC engine, one as a 383 (3.75" stroke + stock bore) and the other as a 377 (stock stroke + big bore) to see the outcome. (Even the same cam was used, which IMO means if it was "right" for one of them, then it was also "wrong" for the other. )

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The two engines performed pretty much as people would expect w/ the 383 making more torque and the 377 pulling a little more peak HP. From what I recall, the differences weren't major, yet fairly predictable.

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