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Old 09-23-2014, 12:01 PM   #1
anarchyburger
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Default Head gasket thickness for my build

I am using a rebuilt EJ257 STi 703 shortblock that has been decked .003 on each side, and rebuilt 04 B25 STi heads that have been machined .001 on each head.

The pistons are Manley 8.5:1 CR platinum series forged. As such, I am not concerned with matching the stock compression ratio. I am more concerned with keeping the same deck size for the sake of the timing belt tension and piston/head clearance.

Just need to verify my thought process is correct here:

Total amount of material removed from the decks is .004 in
.004 inches = 0.10mm (rounded)
Stock EJ257 Head Gasket is roughly .6MM
So I should run roughly a .7MM gasket to account for the machined decks.

So I am looking at the Tomei 1363101071 .7MM gasket set.

The only thing I am unsure of is whether these measurements are uncompressed or compressed and I keep reading mixed information when I search around.

Also, should I still go with the LIC adjustable timing idlers in this scenario?
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Old 09-23-2014, 04:09 PM   #2
fastblueufo
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Your way over thinking things technically. That small amount that was cut won't have any meaning when choosing hg thickness. Just run stock .78mm and stock timing pulley components.
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Old 09-23-2014, 04:15 PM   #3
anarchyburger
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Quote:
Originally Posted by fastblueufo View Post
Your way over thinking things technically. That small amount that was cut won't have any meaning when choosing hg thickness. Just run stock .78mm and stock timing pulley components.
Haha okay. It's my first "build" so I am just paranoid about blowing things up due to oversight.

Thanks for the info.
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Old 09-23-2014, 04:45 PM   #4
yamahaSHO
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I started with a new block, Manley 8.5:1 pistons and the heads were shaved .005". I used stock gaskets and LIC adjustable timing belt tensioners. Motor runs fine.
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Old 09-23-2014, 05:09 PM   #5
Cinic
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Don't forget to hold the government.
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Old 09-23-2014, 05:47 PM   #6
anarchyburger
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Quote:
Originally Posted by Cinic View Post
Don't forget to hold the government.
After many years of having this username on NASIOC, you may be the first that has noticed it
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Old 09-23-2014, 06:26 PM   #7
Cinic
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Hehe...not exactly a mainstream reference.

Good luck with your build.
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Old 03-01-2015, 12:20 PM   #8
jsubaru04
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Default head gasket

Quote:
Originally Posted by anarchyburger View Post
I am using a rebuilt EJ257 STi 703 shortblock that has been decked .003 on each side, and rebuilt 04 B25 STi heads that have been machined .001 on each head.

The pistons are Manley 8.5:1 CR platinum series forged. As such, I am not concerned with matching the stock compression ratio. I am more concerned with keeping the same deck size for the sake of the timing belt tension and piston/head clearance.

Just need to verify my thought process is correct here:

Total amount of material removed from the decks is .004 in
.004 inches = 0.10mm (rounded)
Stock EJ257 Head Gasket is roughly .6MM
So I should run roughly a .7MM gasket to account for the machined decks.

So I am looking at the Tomei 1363101071 .7MM gasket set.

The only thing I am unsure of is whether these measurements are uncompressed or compressed and I keep reading mixed information when I search around.

Also, should I still go with the LIC adjustable timing idlers in this scenario?
sorry to bring this back from the dead but im having a similar problem as your trying to decide on a thicker head gasket ,the deck of my block was resurfaced machine shop took 0.002 thou and the heads were also resurfaced they took 0.005 off each head thats 0.007 thou total so could I still used the oem thickness head gasket which is 0.023in/.6mm thick or should I go with a tomei 0.027 in or .7mm or cosworth 0.030 in /.78mm thick? what did you ended up using on your build?
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Old 03-01-2015, 12:57 PM   #9
anarchyburger
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for what it's worth, I ended up going with the thinnest Tomei head gasket, which is .7mm. Only .1mm thicker than stock. So far so good... 3,000 miles on the motor, definitely have been putting it through its paces

The quality of the tomei gasket was top notch, would definitely recommend it, especially now that they have dropped the price.
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Old 03-01-2015, 03:11 PM   #10
jsubaru04
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ok that's the same one I was thinking in buying as well .7mm tomei
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Old 08-06-2018, 02:00 PM   #11
subiscooby168
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Hi I was reading your thread on Head gasket gapping.
The issue I currently have was while machining the cnc face cutter accidentally dropped and 30 thou had to be taken off overall instead of a standard 5-10 tho. In your opinion can I still use these heads? If so can i use a stock thickness gasket from felpro?
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Old 08-06-2018, 03:50 PM   #12
ripman
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You'll need to check the FSM for the minimum head deck thickness.
Check the cc of the chamber for static compression ratio calcs.
Check piston to valve clearance/

Did a shop do this or you have access to a milling machine?
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