technical question settle debate pls

[bababoy]

ok here the debate - this person says that if i change the stroke, going to a longer one, he says the crank speed will go up. i on the other hand figure its going to take longer since i have to cover a longer distance. wouldnt going to a long stroke generally lower the rpm?

[megomaniac]

stroke isn't really going to affect your rpm. a stroker motor will make more torque at a lower rpm though.

if a stroked motor and a non stroked motor are running the same rpm, the "piston" speed will be higher on the stroked motor cause it has to cover more distance at the same rpm as the non stroked motor. A stroked motor won't seem as "revvy".

[bababoy]

would you be able to achieve the sme engine speeds with a stroked motor?

[riot]

I think the person meant to say piston speed. A stroked motor at a given RPM (we assume for a moment that your stroker will achieve the same RPM as the stocker) must necessarily have a higher maximum piston velocity - and also a greater acceleration at TDC BDC. Piston acceleration is really what you worry about, but engine guys like to look at piston speed as an indicator.

RPM = Crank RPM, if they're the same - they're the same.

Your torque will definitely go up with a stroker. Unless the stroked engine can achieve the same RPM (or therebouts) as the stocker, peak power may not go up. Power = Torque X RPM (with conversion factors of course).

[bababoy]

aahhh.. so what im getting is that a stroked motor would have to go a bit slower in terms of piston?/engine? speed because of the the stress on the piston would be greater if it is asked to achieve the same rpm as the short stroke motor?

[riot]

Yup.

But depending how you do the mod (added stroke amount, cam and spark timing revisions) there is no reason to assume that it won't rev as high, nor that it won't be able to take it.

[JSLincks]

Sounds like you have the info you were looking for, but I'll add this for some simplicity.

Longer stroke = more torque at low rpm's
Shorter stroke = more HP at higher rpm's

With sumos most of us are looking for more power down low.

In the late 60's Chevy took their 327 small block engine (4" bore x 3.5" stroke)
and destroked it to 3.25". This made the famed 302 Z/28. It provided more power at higher rpm to compete in circle track racing. The motors were always revving from 5000 to 6850 rpm which was at the upper range.

[moisey_4]

I'd rather be stroked