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Header bolt length?

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What was I sayin' about my last post about headers?, LOL!!!

I used 1 inch 12 point header bolts with lock washers, but when I got to the last one, it was only 3/4 inch long. With the lock washer it didn't seem long enough, it did take hold to the head, but I was weary of it, so I eightysixed the washer. Will this be a problem down the road? It was the bolt closest to the firewall too. PLEASE don't tell me it is going to have to come out.....

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Discussion Starter · #2 ·

I would take it out. My thinking is that if you were only able to screw it in by removing the lock washer, you might only be catching a few of the threads. It would be in your best interest to have a bolt that is catching more threads, which means, getting a longer bolt. Also, you need a washer for most cases. It helps distribute force and the locking one will help it to stay in place.
Header bolts always need to be retorqued and if you have a bolt that is only screwed into a few threads some torquing might strip them out and then you will have problems and those areas near the firewall are not the best place to have to heli-coil a bolt hole

10,537 Posts
Well, let's see....your header flange is likely .312" thick....then add maybe .100" for the gasket...that would use up about .412" of the .750" of bolt reach....that leaves about .338" in the head threads....

Generally, for a fastener to develop full torque and retention, it requires a thread depth equal to or greater than the OD of the this case .375"...

You're a little short, buddy....*G*

Get the 1" bolt, use the lockwasher and do it right the first're so close now, why sell yourself short...?

If you absolutely have to use the short bolt, swap it with an interior header bolt and use some blue loctite on it to hold it in place...the stresses on the bolts aren't as great in the middle of the flange as at the edges...


Discussion Starter · #5 ·
The only thing I can think of why they may have given you a short bolt is perhaps some cars can't get the full length bolt into the hole, like around the shock towers. I had a tough time getting the one near the #2 cylinder in for the stock manifold.

Considering you can get the full length bolts in all of the holes I'd remove the short one.
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