destroyerSS

iTrader: (2)

Ok i have a 408 W/ AFR 225's that were milled to 69cc.
i have have to do some work to my car and i will be removing my heads and while there off i'm thinking about milling them another 30 Thou to get them to 63-64cc. How much will this help my compression with the large cam i have. Cam is 253-257 643/645 112+4. Is this worth it?
Thanks Shawn BTW car made 512RWHP 484 RWTQ with about 10 miles on the new motor!!

destroyerSS

iTrader: (2)

where are the head experts when i need them

FigsZ28

iTrader: (70)

I just spoke with Tony about this yesterday, Im having mine milled to 69cc to increase my CR. According to him you dont want to mill them any lower than 66cc or else your going to start messing with flow #'s. BTW with a cometic .040 gasket and 69cc youll yeild right at a 11.7 CR.

destroyerSS

iTrader: (2)

I come up with 11.3-1 w/ 69cc and my current felpro .041 gasket. Did i figure wrong? Maybe i can go down to 65-66cc and run a thinner Cometic gasket cause i would like to get to 12-1 comp

FigsZ28

iTrader: (70)

o forgot to add that was with a flat top piston with 2cc valve reliefs. you can also try this page to figure out your CR http://www.rbracing-rsr.com/compstaticcalc.html

destroyerSS

iTrader: (2)

Any other opinions!!

JakeFusion

iTrader: (7)

Mill it another .018" and get it to 66cc. 11.9:1 CR then, assuming the engine was assembled at .000" deck height. If that's the case, you can run a .030" Cometic without worry and mill it down and get 12.25.

destroyerSS

iTrader: (2)

What kinda gains do you think this would yield?

Ryne @ CMS

iTrader: (10)

well my cam is very similar slightly larger, and i am a 408, out of the box afr's 225's with 72 chambers around 11.5:1 compression, i am making 550 rwhp, 501 rwtq

destroyerSS

iTrader: (2)

How did you get 11.5-1 with the 72cc chambers?
also any dyno tricks?
also my car made the 512rwhp with less than 10 miles on the motor and the tune is not a final tune so i think the is more in it as is

Slowhawk

iTrader: (12)

First we need to know what pistons are in there as long as the piston height out of the hole.

I did a 408 with -4CC pistons with the piston out .008,.042 Gasket and 66cc heads.Ran a 244/248 Cam and made 530hp/510tq with 19 degree's of timing.The midrange was nice with 500hp at 4500rpm up.

destroyerSS

iTrader: (2)

not sure if this is it but on my build sheet it say's piston to bore .004 & deck height is 9.235 . Piston are Wiseco flat top w/ 2 1/2cc valve reliefs and lateral gas ports

Tony Mamo @ AFR

iTrader: (13)

Not sure of where you are looking to be when the smoke clears on final CR, but just as a reference, assuming your pistons are .008 out of the hole and we run a .040 thick head gasket, with the 2.5 cc negative piston volume you claim to have, a 67 cc chamber will yeild exactly 11.74 to 1 CR.

Not sure whether you are looking for more than that, but you are going to have a tough time running pump fuel with that high a static CR.

Sunoco 94 would probably work and 93 octane is very dicey....everything has to be perfect. Sure you will be able to drive around but you might get a little KR at WOT when the cylinder pressure is at it's highest. If your willing to splash a little racegas or use some form of octane booster it shouldnt be a problem. You need to measure how much your pistons are out (or in) the hole at TDC....dont trust "deck height" numbers and math....you need to physically take proper measurements....

Tony M.