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Deck Thickness, How Thin is Too Thin? #2856492
12/07/20 12:07 PM
12/07/20 12:07 PM
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Northeast Indiana
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73DAD Offline OP
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How thin of a deck would you consider as a 'no go'?

My beater '66 hemi block is already .080" shorter than nominal, it needs further milling from some gouges in the deck. Some gorilla tried to pull out the 1/4" dowels with vicegrips & scarred it up. I haven't had the deck sonic'd yet, was just looking for some reference.

Street use, standard head bolts/stud, stock iron heads.

Re: Deck Thickness, How Thin is Too Thin? [Re: 73DAD] #2856496
12/07/20 12:14 PM
12/07/20 12:14 PM
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This may be of help.

Decking Thread


"We live in a time when intelligent people are being silenced so that stupid people won't be offended".
Re: Deck Thickness, How Thin is Too Thin? [Re: 73DAD] #2856518
12/07/20 12:59 PM
12/07/20 12:59 PM
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A727Tflite Offline
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Originally Posted by 73DAD
How thin of a deck would you consider as a 'no go'?

My beater '66 hemi block is already .080" shorter than nominal, it needs further milling from some gouges in the deck. Some gorilla tried to pull out the 1/4" dowels with vicegrips & scarred it up. I haven't had the deck sonic'd yet, was just looking for some reference.

Street use, standard head bolts/stud, stock iron heads.


Back in the day a lot of guys cut the deck .100” without any problems after. That’s running in Super Stock at 12.5 - 1. Plain old steel gasket too.

Re: Deck Thickness, How Thin is Too Thin? [Re: A727Tflite] #2856546
12/07/20 01:47 PM
12/07/20 01:47 PM
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hemienvy Offline
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How does the spacer plate work ?

Is it: Block - steel shim - spacer plate - steel shim - Head ?

Re: Deck Thickness, How Thin is Too Thin? [Re: 73DAD] #2856602
12/07/20 03:14 PM
12/07/20 03:14 PM
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Shelby Twp. Mi
HardcoreB Offline
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The reality is that it's probably not near a critical sealing area...hopefully anyway. After you gauge that, just flat-file the high spots down. We won't tell anyone it's got an aesthetic hidden flaw.

Re: Deck Thickness, How Thin is Too Thin? [Re: hemienvy] #2856608
12/07/20 03:22 PM
12/07/20 03:22 PM
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Originally Posted by hemienvy
How does the spacer plate work ?

Is it: Block - steel shim - spacer plate - steel shim - Head ?


That’s the way we have done it.

Re: Deck Thickness, How Thin is Too Thin? [Re: 73DAD] #2856611
12/07/20 03:23 PM
12/07/20 03:23 PM
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Originally Posted by 73DAD
How thin of a deck would you consider as a 'no go'?

My beater '66 hemi block is already .080" shorter than nominal, it needs further milling from some gouges in the deck. Some gorilla tried to pull out the 1/4" dowels with vicegrips & scarred it up. I haven't had the deck sonic'd yet, was just looking for some reference.

Street use, standard head bolts/stud, stock iron heads.


If the marks are not in the load cell/bead area of the gasket then as mentioned, just lightly file to get any high spots out and be done with it.

Re: Deck Thickness, How Thin is Too Thin? [Re: A727Tflite] #2856619
12/07/20 03:31 PM
12/07/20 03:31 PM
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hemienvy Offline
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Thanks Transman, I have been thinking about this.

What kind of compression or boost were you running with the spacer plate ?

Re: Deck Thickness, How Thin is Too Thin? [Re: A727Tflite] #2856648
12/07/20 04:13 PM
12/07/20 04:13 PM
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Northeast Indiana
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73DAD Offline OP
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Originally Posted by Transman
Originally Posted by 73DAD
How thin of a deck would you consider as a 'no go'?

My beater '66 hemi block is already .080" shorter than nominal, it needs further milling from some gouges in the deck. Some gorilla tried to pull out the 1/4" dowels with vicegrips & scarred it up. I haven't had the deck sonic'd yet, was just looking for some reference.

Street use, standard head bolts/stud, stock iron heads.


If the marks are not in the load cell/bead area of the gasket then as mentioned, just lightly file to get any high spots out and be done with it.


I wish the marks were just cosmetic, but they managed to gouge all the way around and over the edge of the nearest cylinder wall, deep. Otherwise I probably would have just run it. Its bad enough I'll have to ridge ream or round file the cylinder lip in that spot.

Re: Deck Thickness, How Thin is Too Thin? [Re: hemienvy] #2856730
12/07/20 07:19 PM
12/07/20 07:19 PM
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Originally Posted by hemienvy
Thanks Transman, I have been thinking about this.

What kind of compression or boost were you running with the spacer plate ?


Had numerous old Super Stock motors that came in that had the old TRW/DirectConnection 12.5 - 1 pistons that guys wanted to run on the street without anything but a smaller cam. Took the rollers out, rebuilt the motors and added the shim with gaskets.

Didn’t have any problems from any of them. You would have to use a compression calculator to figure out what actual ratio they ran at.

We did use the shim on a motor that was whacked way too much but was used in MP at 12.5 to 1 with no issues either.

Last edited by Transman; 12/07/20 07:21 PM.
Re: Deck Thickness, How Thin is Too Thin? [Re: A727Tflite] #2856791
12/07/20 09:01 PM
12/07/20 09:01 PM
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Frostbitefalls MN (Rocky&Bullw...
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That might be an easy fix at a diesel welding shop. Weld up the gouges, take only .005 cut or so to fix.

Last edited by gregsdart; 12/07/20 09:02 PM.

8..603 156 mph best, 2905 lbs 549, indy 572-13, alky
Re: Deck Thickness, How Thin is Too Thin? [Re: A727Tflite] #2856933
12/08/20 08:49 AM
12/08/20 08:49 AM
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Northeast Indiana
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73DAD Offline OP
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Ever double stack steel gaskets with a spacer plus another on the other side?

.021+.021+.059+.021

I've got all those on hand already, that would let me shave .010" from the block to clean it up and the compression would still be happy.

I'd hate to pony up for Cometics if I don't have to. Everything's been pretty low-buck up to this point.

Re: Deck Thickness, How Thin is Too Thin? [Re: 73DAD] #2856970
12/08/20 10:41 AM
12/08/20 10:41 AM
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St. Paul , Mn.
tubtar Offline
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G.M. used to stack steel shim head gaskets on the 409's in 1962 to get compression down to one that would like pump gas...........lowered it to 11.5 - 1 as I recall.
Back when Fred Flintstone moved his car through the courtesy fo his two feet.
If I was building a Hemi , I don't know that 250.00 for a set of head gaskets would be unexpected.
I'm all for saving money , but using a bandaid to fix something critical just seems wrong.

Re: Deck Thickness, How Thin is Too Thin? [Re: tubtar] #2856981
12/08/20 11:02 AM
12/08/20 11:02 AM
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I am kind of confused by the question/answers. Doesn't this all revolve around the stroke, rod length, and piston CD along with desired compression? You can get thicker cometic to compensate if you need. But have seen blocks decked that much that have been used in race motors and street motors. Ideally you rather have thin gasket and thick block, but you can't change that now.







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