I recently ordered AFR 74 cc heads for my new engine and they are going to yield about 9.2:1 compression. Would I be going to high in compression if I change my order to the 58 cc heads that they sell?

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Riccioli Performance Motorworks

--RPM Racing--

-Currently building first ever engine. 383 with Super Ram plenum and runners, Edelbrock lower intake, Bosch 24# injectors, AFR 190 heads, MSD ignition.
-Will be installing Baer Brakes
-Will be installing full Spohn suspension in rear
-Art Carr 700R4 trans??


Attention Everyone!!! I will be changing my name on the message boards to HardcoreZ28 sometime in the near future. Just wanted to let everyone know.

 

You'll be at about 10.6:1 on a 383 going from 72cc to 58cc. You'll have to decide for yourself if that's too high (probably is).

 

Use one of the compression calculators to figure out your ratio. I'd run 11:1 if I were you.

 

Is the 58cc a typo? I'm also a first time 383er looking at AFR heads and comp ratio's and I was led to believe the options were 68 and 74cc.

 

Oh yeah 68cc........my mistake.

 

Paul, what is the deck height of your block or better yet what is the block deck to piston dimension? Are you using notched flat tops? If so,I'm thinking that you just might want to go to the 68cc, with pump gas.

As long as you're spending the bucks you might as well go for as much kick as you can.



[This message has been edited by Changa2 (edited April 01, 2001).]

 

Notched flat tops. I forget the deck height.

 

It depends alot on what cam you are running.

IMHO with any cam that is appropriate for those heads - that is, any cam that opens the valves far enough and long enough to take addvantage of their flow characteristics - 9.anything CR is too low. 10.6 would be near ideal. I'd be shooting for between 10.5 and 11. That should behave about like the same motor would if the CR was in the 9.8-10.3 range with iron heads.

I recently had an opportunity to pick up some 74cc AFRs for my 400 at a good price but passed it up because I'd rather have the 68s. The 74s would be perfect for a nitrous or hair-dryer setup, not quite right for N/A.

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