[Cliff R]

Right on the dyno we made 424hp/465tq with a Pontiac 400 with unported #16 heads. The compression ratio was just over 10 to 1, and we used a 228/235/112 camshaft. That engine was using a stock iron intake and Q-jet.

KRE did the same build with a set of their 65cc aluminum "D" ports and made 440HP (unported heads).

Drop the same engine back to 9.5 to 1 and put in a smaller cam and you'll be hard pressed to make 400hp, probably closer to 350-375.

One of our customers did the ever popular 400 cid with heavily cut 6X heads and the XE274 camshaft and made 380hp and close to 425tq. Still PLENTY of power for a decent burnout in a hard right hand turn leaving Dairy Queen!

As you can see, there is a modest power difference with more compression and the right camshaft......Cliff

[bobzdar]

Fwiw, I'm running unported 16's on an .030 400 with a 744 cam (224/236 @.050" 115.5 lsa) with no detonation on pump gas. Right around 10:1 compression.

There's no magic number as if you put the wrong cam in, it can detonate at 9.5:1. If you have mildly ported heads and a larger cam, it can run fine at 11:1.

What are your constraints? So far we have unported d-ports on a 400. What's the intake, transmission, rear gearing, etc? Or have you yet to select them? All of those factors will determine the rpm range of the engine, which will then influence camshaft selection, which will then determine your safe CR.

[aktattoo]

This might be enough to confuse you but, its an explanation of how things coexist in that realm.

http://www.thepontiactransampage.com...blueprint.html