What size Head gasket?

David D

New Member
Oct 19, 2008
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Califfornia
What size head gasket do I use if I have a 0.50 overbore on my block. Will a stock head gasket size sufice or do i need an 86mm bore head gasket.

Thanks again.
 

radiod

Supramania Contributor
Dec 13, 2007
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I sure hope you mean 0.050", I don't think 0.50" is even possible.

0.050" = 1.27mm
Stock Bore = 83.0mm (3.267")
New Bore = 84.27mm (3.317")

In otherwords, don't get an 84mm bore gasket, 85mm or 86mm should work fine. I know for a fact most HKS head gaskets are 86mm by default to make up for overbore.
 

David D

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Oct 19, 2008
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Califfornia
well the pistons i got were advertised as 0.50=00.20" what should i do :1zhelp: the pistons are 00.20'' is a stock head gasket ok to use?
 

radiod

Supramania Contributor
Dec 13, 2007
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How much did the machine shop overbore? Can you provide a link or brand/part# of the specific pistons? Double check your numbers and make sure you are getting the decimal in the right spot and your form of measurement right (inches vs mm). 0.5mm = 0.020" if that's what you were trying to get at with your piston size, and if you overbored 0.5mm NOT 0.5" (impossible, but 0.050" is possible), then you're at an 83.5mm bore.

Get your numbers and measurements straightened out in your own head and then we can help you more.


Why the hell did we have to half adopt metric and half stay with english measurements? A classic case where a little misunderstanding can lead to serious consequences....
 

hvyman

Dang Dude! No Way Man.
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Apr 17, 2007
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you cant bore a block 50 over with out running into issues with the thickness between the cylinders. that and i have never seen 50 over pistons. i think he means .5mm or .020 over.

stock is 83 so a 84 mm will be fine. when you get the hg just lay it down on the black to make sure.
 

lewis15498

Don't blame ebay cheapass
Sep 28, 2008
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David D;1380771 said:
Ok sorry for the confusion. I really appreciate all of your help.. here is the link to the pistons I bought and the size is (.50mm = .020")....http://cgi.ebay.com/ebaymotors/ws/e...witem=&sspagename=STRK:MEWNX:IT#ht_3538wt_925..... with this infomation do u think i can still use a standard size head gasket or do i need a one with a bigger bore.


Thanks again guys :icon_razz

lets review. stock bore is 83mm, you added .5 mm. Your new bore is 83.5mm. An 84mm bore hg will work just fine. you are looking to have your hg bore be slightly greater than, or equal to your cylinder bore.
 

radiod

Supramania Contributor
Dec 13, 2007
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lets review. stock bore is 83mm, you added .5 mm. Your new bore is 83.5mm. An 84mm bore hg will work just fine. you are looking to have your hg bore be slightly greater than, or equal to your cylinder bore.

Done and done.