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FWIW, I built a 360 with magnum heads, zero deck flat top pistons and a 224/230 @0.050 cam which is 10.6:1 compression and has 180-190 psi cranking pressure.

I run this engine on 89 octane and in a pinch can run 87 if I am careful. The key is the tight quench of the flat top pistons and closed chamber heads.

If you crank the numbers through Camquest it should be 410 HP. I figure its around 370 HP based on 102 mph trap speeds in the 1/4.

Sometimes I feel like the world has passed this old fart by.
I have been wondering how these new cars (especially my new Challenger) are getting by with these high compression ratios, and crap gas.
So you are saying it is because of the elimination of the quench area? Maybe just changing heads to Magnums?




Not the elimination of the quench, I have an ideal quench. Flat Top piston coming very close (0.039") to the flat closed area of the chamber. As the piston approaches TDC the fuel/air in the closed area is squeezed at high velocity towards the plug. This creates a lot of turbulence which makes the engine very detonation resistance and reduces the amount of timing needed for max power.

You can use a pop-up piston with an open chamber but unless the piston matches the profile of the chamber closely it is less than ideal.

Magnum heads typically have around 64cc chambers. They use a pedastel mounted rocker system so the orlder shaft rockers don't work. Studs and guide plates are available to allow the use of sb Chevey roller rockers. They also require the use of hollow push rods and lifters that provide push rod oiling for the rockers. The intake also uses vertical mounting bolts so you need either a magnum specific intake or have the heads redrilled to accept LA style mounting.

Dave Clement Pembroke, MA 03 PT Cruiser GT Turbo 99 Dakota SLT+ CC 4x4 68 Barracuda sport coupe http://home.comcast.net/~dgc333/