What is the ideal total deck height?

[arneoe]

Assuming a mechanical safe minimum total deck height (inclusive head gasket) of .035” for engines with standard rods for less than 6500 rpm, what is the ideal quench deck height? Some say 040” - .050”, some .050 - .060 and others say this is an irrelevant issue based on rumors among certain amateur tuners. So far I have not found any mathematical or scientific proofs, so I gather that it must be based on trial and error. What is your experience regarding this when talking about detonation issues vs total deck height?

For my 383 build I have a block deck height of .010" and I have to chose from:

- .072" total deck height with static CR of 9.9:1


or

- .051" total deck height with static CR of 10.3:1

The cam is a COMPCAMS XE-268H

your opinion please.

Arne

 

[Red]

I also have an interest in what the gurus say. One builder who i spoke with suggested decking to within .005 of zero. Using your numbers, this would make his recommended quench .040. This is with a 355 cu in, aluminum heads and hyd roller cam with about .540 lift and burning 93 pump gas. I'm assuming no more than 10.5:1 CR.

 

[arneoe]

Anyone please, I need to make up my mind which head gasket to install...It is nice to have someone to put blame on if it does not work.. :lol:

Arne

 

[Twin_Turbo]

You mean quench height? Depends on the kind of engine, if NA over .065 there's not much quench left. You want it narrower but not too narrow so that a stretching rod makes that the piston smacks against the head.

Ideal would be a deck height where you can choose the gasket to set the proper quench. Std your deck height will be around 9.025" and the piston @ TDC will sit below 9.000" usually around 8.995 or even a little deeper. That means that not decked you already have .030 there. With a thick .035 gasket your quench is out the window.

So you have a 9.010 decked block, do you know where the piston sits @ TDC? That's needed for an educated decision. i would stick with .040 for quench height also.


XEH268H huh? Better run that puppy with just the outer springs and doped up oil.

 

[JAKE]

When I have the machine work done I prefer a ZERO deck height with the piston deck level with the block amd choose a head gasket that results in no more than .040 quench clearance.

A ZERO deck height eliminates the dead space between the piston and deck and the head gasket selection establishes the quench clearance. In the few cases where I've had to run a head gasket thicker than .040 (compressed), I've actually run the piston deck out of the hole.

In most cases, a ZERO deck and a .040 gasket gets it done with no problem.

Jake

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