Decking the Block

[68Charger 440HP]

I was just wondering if i deck the block, do i have to shave the intake side on the heads to make the manifold fit correctly? I have never heard anything about doing this so i am not sure. I got to thinking and realized that maybe decking the block will change the angles of the heads. Does anyone know about this or had experiences doing this? Thanks guys.

[451Mopar]

Decking the block or heads moves the heads closer together, but the angles remain the same. In short, yes, you probbly will have to mill the intake manifold or the intake side of the cylinder heads for the correct fit if you assemble the engine with stock thickness gaskets.

The larger gasket thickness of the aftermarket (Fel-Pro, etc.) gaskets can help compensate for the milling, so If you milled 0.020" off and used the Fel-Pro gasket that is about 0.020" thicker than stock, everything should line up, but the compression ratio would remain about the same.

[68Charger 440HP]

My first plan was just to shave the chambers of the heads .060 and the intakes .074. I later decided that i wanted to take a little off the deck just to make sure it was level. I was thinking .010 off the deck, .050 of the chamber of the head and .062 off the intake of the head. But, if decking will also change angles then i might just shave all off the heads. I don't know of any ratio for deck to intake of the heads. I don't want to shave my manifold because it can only be used with those particular heads. Which way should i go in this case? All input is appreciated. Thanks.

[DartGT66]

It's just the same thing wether you mill the heads or the block; you'll move the heads closer together and have to mill the intaqke face to make it fit. Usually you can mill about.030" and still be able to fit the intake without problems; the production tolerances were so big that a .010 difference is totally meaningless what comes in to mainifold fitment.

[SubLime440]

What is usually the maximum for shaving off of the heads before valve to piston clearance becomes an issue. Also how much of a C-R change does this create as I am also thinking about shaving my new fully ported 906's down.... Or is it really worth it at all?

[70gtx]

hi,i asked some of the same questions , if you look back to oct.31 (head shave) or 70gtx.i guess it is unknown exactly how much c/r is gained . i read on another post a guy had .15 deck to piston,.060 head shave &use a .020 gasket and came up to 9.1 :1.maybe some of this can help but im going to talk to machine shops around to see if i can get some more information.

[DartGT66]

Basically with CR and valve to piston clearances, don't assume anything, always measure. The influence of milling the heads or block has very much to do with your current true CR, engine displacement, combustoin chamber area etc. etc. There are too much variables to give a ball point figure without knowing these things first. Also, check the valve depths by putting a straight edge over the valve stems; they can vary quite a lot and that has an effect on the valve to piston clearance too, I just recently learned.

[68Charger 440HP]

Sublime, I would say that if you have the clearances then yes, shave your heads. You will gain a lot from 1 point of compression. There are many clearances you must be aware of. Piston to valve, piston to head, you must know the valve lift. You must also be sure that your compression is not over 9.5:1 unless you are using race gas. Like Dart said, don't assume any of your clearances. You'll have to measure them. Just incase you are interested .020 in and one third of a compression point. Good luck with your decision.