Block decking, and head alignment

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Dec 5, 2003 | 11:39 AM

spud

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Joined: Jul 1999

Posts: 347

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From: Marshall,IL

Car: 82 & 91 Firebird

Engine: 400 & 355

Transmission: TH350 & 700

Axle/Gears: 4:11 & 2.72

Block decking, and head alignment

If you have a block decked how much material needs to be removed, before you have to have the heads, remachined to align with the intake.

My 400 needs 30 thousandths removed.

Thanks
Spud

Dec 5, 2003 | 12:12 PM

88IROC350TPI

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Joined: May 2001

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From: Pitman, NJ

Car: '89 IROC-Z

Engine: Canfield 195 headed 358ci

Transmission: TH350, Art Carr 9.5"

Axle/Gears: 3.92 Dana 44

My block was 0-decked and required no machining to the intake or heads for them to align.

Dec 5, 2003 | 02:00 PM

ede

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Joined: Aug 1999

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From: Jackson County

i've never had a problem with intakes when i removed metal from the block. just got a set of heads and pick up block next week that have both had metal removed so i'll see what that does

Dec 5, 2003 | 02:12 PM

Free Bird

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From: Dale City, VA

Car: 91 GTA and 85 IROC

Engine: 355

Transmission: gear jammer

Axle/Gears: 4.11

There is a formula for that. But I'll be damned if I can remember it now. I'll look through some notes.

0.030 is quite a bit, but I don't think you'll have any major problems.

Dec 5, 2003 | 02:52 PM

wesilva

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From: Albuquerque, NM

Car: 1966 El Camino Custom

Engine: 350

Transmission: 200R4

Axle/Gears: 3:73 12 bolt with Brute Strength

Your block should have come from the factory approximately with a 9.025" deck. 030" would probably put you below 9" which is the standard that most pistons are set for as far as comp. height. Your pistons will probably be just above the deck after being machined.

The standard accepted head deck to block deck clearance for steel rods is about .035". To maintain this on a block decked below 9", you will have to run a fairly thick head gasket to maintain that .035" clearance. Any quality head gasket in the .045" to .060" range would be good. DO NOT RUN A SHIM GASKET AFTER YOU GET THE BLOCK BACK!!

You also might consider running the Moroso plug deck stiffeners. They are just a NPT 3/4" plug with a 5/16" hole for head cooling. Typically, because I use my cars just for street use, I will drill these out to about a .400" hole. I like the deck strengthening but like my heads to cool normally.

Last edited by wesilva; Dec 5, 2003 at 03:53 PM.

Dec 6, 2003 | 01:32 PM

AJ_92RS

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Joined: Apr 2001

Posts: 4,969

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From: USA

Car: yy wife, crazy.

Engine: 350, Vortecs, 650DP

Transmission: TH-350

Axle/Gears: 8.5", 3.42

Straight from John Lingenfelter's book
John Lingenfelter on Modifying Small-Block Chevy Engines, pg. 95

Quote:

Anytime either the block deck surface or cylinder head dack surface is machined, this changes the relationship of the intake manifold and cylinder head sealing surfaces. To restore this relationship and improve intake manifold gasket sealing, it's often necessary to mill both intake port sealing surfaces as well. If the heads and/or block is milled less than .020-inch, milling the intake is usually not necessary. All dimensions are in fractions of an inch.

Block/Head.................Intake Manifold
....................................Side...Bottom

.010---------------------.012----.017
.015---------------------.018----.025
.020---------------------.025----.034
.025---------------------.031----.043
.030---------------------.037----.052