Exhaust header bolt question.

[LinceCuda]

My 71 340 engine has a pair of 74 360 modified J heads. The issue I have is I purchased a pair of stainless steel headers that came with 5/16" x 1" bolts. The bolts are to large diameter wise to fit the mounting holes on my heads, 1/4" is the correct diameter. I can't find anyone who sells that size header bolt, ant of y'all have a contact I can purchase these from. I've posted pics of the bolt and another bolt I cleaned the end up on just to check it fit and I wasn't going 

[Chryco Psycho]

I have not ever seen a small block head with 1/4 exhuast bolt holes , they should be 5/16"
were the heads repaired , altered ?

[LinceCuda]

I have not ever seen a small block head with 1/4 exhuast bolt holes , they should be 5/16"
were the heads repaired , altered ?

The heads were ported and the larger 2.02 valves installed other than that nothing that i could see. Well that being said I guess I can take a closer look and see if they were helicoiled. I'll go look and take a pic.

[LinceCuda]

Psycho looks like they've been coiled, you agree? Here's some pics.

[Strawdawg]

looks like someone did not want to drill out the holes to fit the correctly sized bolt when they coiled the holes

[Chryco Psycho]

  looks like they installed inserts & went a size smaller , 2 problems 1 it will be tough to achieve the required torque with a 1/4 bolt as it may break & no small head  header bolt type fasteners available for that . Not good

[LinceCuda]

Well I got to looking at the bolt I cleaned up and used to test fit into the heads because it just didn't look small enough to be 1/4". So I searched and found my bolt sizer and the test bolt was indeed 5/16. So long story short the company sent 3/8 bolts instead of 5/16 that would have been correct for mounting my headers. The other good news is that the heli-coils installed were done correctly and my headers pulled up nice and tight. The company did offer to send me a $15.00 refund check to cover the cost of bolts I bought and I accepted. So I feel alot better knowing I don't have to drill out the mounting holes but also a little foolish that I didn't pay more attention to what I was looking at bolt wise.

[RUNCHARGER]

There you go. Common misteak with SBD.