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Header bolt size please.

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Old Mar 4, 2006 | 07:37 PM
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Default Header bolt size please.

I see ARP sells 3/8" X 0.75" and 3/8" X 1.0" header bolts. I know I need sixteen of them but which length? 1.0" or 0.75"?

These are for an 02 Z28 with GM gaskets and Kooks headers.

Thanks!
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Old Mar 4, 2006 | 11:24 PM
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I belive they are 8mm by 25mm and you only need 12
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Old Mar 5, 2006 | 10:37 AM
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Ok, looking at my header sitting in the living room, I see six per side.... = 12 total lol.

25mm is real close to 1". I know people re-use the stock bolts all the time, but I also read of people snapping them off and stripping them. I'd really like to end up with the exact same length of threads in the head.

I might just remove one from the car a take some measurements.
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Old Mar 5, 2006 | 01:06 PM
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reusing the stock bolts is not a good idea because you would have to put washers to make up the difference in the thickness between the stock exhaust manifolds and the new headers, The 3/8 thick will not work because i tried them.
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Old Mar 5, 2006 | 06:24 PM
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Originally Posted by akZ28
reusing the stock bolts is not a good idea because you would have to put washers to make up the difference in the thickness between the stock exhaust manifolds and the new headers, The 3/8 thick will not work because i tried them.
OK, so the stock bolts are 25mm in length and they are too long to use with Kooks headers?
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Old Mar 5, 2006 | 06:30 PM
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You can reuse the stock bolts. The flange thickness of the kooks headers should be nearly identical to the stock manifolds.
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Old Mar 5, 2006 | 07:10 PM
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Originally Posted by BackinBlack02SS
You can reuse the stock bolts. The flange thickness of the kooks headers should be nearly identical to the stock manifolds.
Thanks for your help. I know I've seen lots of people reuse the stock ones but I want new ones.

I noticed that the LSx Stage8 locking bolts are listed as being 8mm-1.25 x 22mm FWIW.
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Old Mar 5, 2006 | 07:44 PM
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Originally Posted by ShevrolayZ28
I noticed that the LSx Stage8 locking bolts are listed as being 8mm-1.25 x 22mm FWIW.
lol they use the same size on the 5.0 Ford.
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Old Mar 6, 2006 | 08:21 PM
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Originally Posted by ShevrolayZ28
OK, so the stock bolts are 25mm in length and they are too long to use with Kooks headers?
my bad didnt read that you were using kooks, i have pacesetters with the smaller flange
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