header bolt help

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Dec 6, 2008 | 02:01 PM

redhot lt-1

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From: sumter,sc

header bolt help

found my header bolts have backed out and lost 1 i bought aftermarket from advance and they were wrong size any body know what size i need the one`s on now have a 10mm head
thanks
redhotlt1

Dec 6, 2008 | 03:13 PM

ThreeHonks

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From: DetroitRacing.com

I have 3/8" bolts and it works fine

Dec 6, 2008 | 03:32 PM

96capricemgr

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The thread is 3/8" coarse and what you have now is probably a 3/8" head not 10mm which is close.

Header bolts back out because gaskets compress leaving no torque on the bolt, next time check the bolts frequently for the first few weeks.

Dec 6, 2008 | 03:47 PM

sz282

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From: Cottonwood, AZ

I also have 3/8" by 3/4" and definetly make sure to check them every couple of days for a week+. I usually check mine immediatlly following the first few drives as well.

Dec 6, 2008 | 05:00 PM

redhot lt-1

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From: sumter,sc

well they`ve been in for over a year. i run a 99 cobra the other week and a few days ago i heard an exhuast leak and found i bolt missing and i backed 1/2 way out. thought the missing one was broken but the bolt hole is clean so it must of already been lose.

Dec 6, 2008 | 05:05 PM

LS1 SPEED

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From: Schaumburg,IL

ARP 400-1209

1"

12 PT 5/16 HEAD

These are all we use on LT1's and have great success. I use them on my own car and after I heat cycle the motor I go back and tighten them 1 time and never worry again.

Dec 6, 2008 | 05:11 PM

Houdini

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From: Central Massachusetts

Quote:

Originally Posted by LS1 SPEED

Big +1 on that!

1" is a very good idea when running headers, at least those that have 3/8" or 1/2" flanges.

I'm running 1" long Breslin's and couldn't be more happy, no leaks and never had to go back and tighten them.