Jughead

In reference to cylinder/heads? How do you get to zero deck height?

What deck height is normal or most common?


thanks
Len

:smash: :smash:

PatsLs1vette

thats where the piston comes to the top of the deck..alot of builders do it at 6 thousandths in the hole..some do it at zero..you can deck the block to achieve the zero or 6 thousandthds deck height too.hows the excursion treating you?
what you do is bring the pistons tdc and then measure with a feeler guage and see how far down the piston is in the hole..

[Modified by pats406nitrovette, 3:54 PM 1/20/2002]


[Modified by pats406nitrovette, 3:54 PM 1/20/2002]

ORVette

It means the top of the piston @TDC is level with the top of the deck. I think most average sm. blocks come in about .020 - .040 in the hole @TDC. What it works out to is the difference between .040 deck height and 0 deck height is about 1 compression point with like head gasket and chamber volumes. A machine shop can probably provide a better explanation than I can, but that's basically it. There's more to it regarding tightening up the quench area and the effect it has on combustion characteristics, but that's over my head.
Troy

mountainmotor

Not all pistons are created equaly in respect to negative deck height.As an example one part# 427 piston comes in at around - .008 compare to another 454 piston that comes in at -.025
These motors must first be mocked up to see how much material must be removed from the deck surface of the block.
This operation is usefull to increase the quench area to promote better combustion and reduce detonation on pump gas.
With a true open chamber head the gain by doing this is about nil other than if you are correcting compression.
This would apply in part to Small Chevy's as well

Jughead

Thanks guys. This question was raised because the Holley SysteMax engine package I'm considering states that there should be zero deck height. What happens if I'm not at zero deck? Compression ratio changes? Anything else? Can I still use their aluminum heads?

Pat, the "X" is one awesome vehicle. Great in the snow, nice stereo, leather & pick-up. good thing we bought it when we did---the next day it was packed with my wife & I and 6 teenage girls going ice skating.

Len

Rockn-Roll

There will be no problems with using the heads on a stock block and pistons with the .025 or whatever below deck. The only problems you could encounter is if the block has been "decked" so that the pistons rise above the deck which could cause contact with the valves in the head and destroy the engine. Don't leave anything up to chance. The only way to check piston-deck clearance is remove the head and place a straight edge across the deck and make sure the piston does not touch the straight edge. There may be some carbon deposits on the pistons, and if so be sure to remove it before attaching a new head.

Ganey

1970 Stingray

The above post by mountainmotor answers.

Yes, you can still use their aluminum heads.

Jughead

Thanks Guys, that's what I thought. The heads are off the block but I haven't measured the deck height yet. Just by looking and feel, with one piston a 0 TDC it's a little lower than the block face, so I shouldn't run into any valve/piston clearance problems.