What's the highest compression I can run on 93 pump gas for my 422?

 

11:3:1

 

I think i have seen 12:6:1

 

12:6:1 ain't pump gas though.

 

11.5-12.0 with the right cam.

 

I think Colonel is running that compression isnt he running pump gas or is he running race gas?

 

Colonel runs 12.2:1 with unleaded 104, but I dont think the motor is at the 104 octane threshold. It would probably run on much less. He has a BIG 112LSA cam as well.

[quote]MTI 422 with their S1 hydraulic cam (244/244 .612/.612 112) 12.2:1 compression (runs fine on pump gas.)
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tighter LSA = more tolerance for compression (less dynamic cylinder pressure)

 

I disagree Ryan. Tighter LSA will increase overlap but it doesn't effect dynamic compression that much.

What we are measuring is static compression. But what we are concerned the most with is dynamic compression, which is effect by how the cam fills the cylinders, as well as the exhuast setup. You can run a very high static compression if you put a huge cam in there to bleed off the compression at lower rpms.

Overlap is when the exh is closing and the intake is open. The time of the intake valve closing has the largest effect on dynamic compression but nothing to do with the overlap.

At your torque peak and above it, the tighter LSAs give you higher dynamic compression as well as more overlap, the opposite for more open LSAs. And thats what we're most concerned with.

I have a very vague idea how intake centerline and retarding/advancing the cam play into this, but not enough to 'splain it.

Edit-your bore size will effect this too. A large bore is always more prone to detontation than a smaller one because the flame has to travel farther.

J.

[ December 01, 2001: Message edited by: Crazyquik ]</p>