851hp 509 ci EMC 2005 Winner

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01-11-2019 | 08:22 PM

#21

hogie roll

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From: St. Pete Beach, FL

Quote:

Originally Posted by getrdunn

If I'm not mistaking MT is trying to say that the 4.5" stroke is bringing peak hp down with the said duration @.050. Without looking into it more I would guess with a 4" stroke 509 ci would likely make peak hp above 7k. That's a given.

No, it’s not a given. In fact it’s wrong. A 509 created via a 4.5” bore x 4” stroke would make the same power within the measurement variance.

Last edited by hogie roll; 01-11-2019 at 08:26 PM.

01-11-2019 | 09:11 PM

#22

getrdunn

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From: NW Michigan

I've have a little different opinion but do realize it's not just displacement and duration that dictate peak hp RPM. Obviously there's other variables. Intake runner length and port volume, int & exh port cc, head degree, LSA, cam timing events/overlap, etc etc. Know you can take a 565 CI with a little 236/244 + - and have peak hp @ 6k.

Just so so I understand what your saying though is a 4" stroke, 4.5" bore 509 build would peak hp as a 4.5" stroke, 4.25" bore with same components. Not arguing at all just always like good topics....

Last edited by getrdunn; 01-11-2019 at 09:20 PM. Reason: Correction

01-11-2019 | 09:13 PM

#23

getrdunn

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From: NW Michigan

I shoulda reread before asking but was that cam installed straight up?

01-11-2019 | 10:08 PM

#24

mike tkach

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From: yorkville,il

Quote:

Originally Posted by hogie roll

No, it’s not a given. In fact it’s wrong. A 509 created via a 4.5” bore x 4” stroke would make the same power within the measurement variance.

i disagree,the combination that does the best job of filling the cylinder will always make more power in a n/a engine.the bigger bore will unshroud the intake valve aiding in filling the cylinder.engine builders have known this for decades.

01-12-2019 | 07:05 AM

#25

MILD THUNDER

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From: chicago

Quote:

Originally Posted by hogie roll

i don’t agree. Displacement is displacement regardless of the bore stroke combo. The head only flows based on the pressure drop created below it. That pressure drop will on average be equivalent for the same displacement at the same engine speed. The only caveat is that the larger bore combo might create a better flowing chamber.

Id attribute the 6400 peak to the very tight lsa. Wider lsa’s can hang on up top better.

You forgot one part. The motion of the piston. A half inch change in stroke, as well as a change in rod angle, is a big player in what the piston does, and when it does it. The pistons movement/speed, plays a big part in cylinder filling. If it didnt, variable camshaft timing wouldnt exist.

The pistons position in the cylinder, varies based on those variables. Therefore, the valves need to compensate for those changes.

01-12-2019 | 09:13 AM

#26

getrdunn

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From: NW Michigan

:A custom cam grinder wouldn't even grind a cam if you didn't give him the stroke in your combo. Ah just don't worry about it dude I said it's gonna be a 572. I mean wtf... What difference does it make how I get there?