1969 Head Bolts

[Brad H.]

I have a 1969 base engine 300hp/350. The engine has been dissassembled for some time and I would like to use new head bolts. Any recommendations on where to get "correct" head bolts for this application? What should the "correct" bolt head design be?
Thanks,
Brad Hood

[Joe L.]

Re: 1969 Head Bolts

I have a 1969 base engine 300hp/350. The engine has been dissassembled for some time and I would like to use new head bolts. Any recommendations on where to get "correct" head bolts for this application? What should the "correct" bolt head design be?
Thanks,
Brad Hood

Brad-----


Original bolts had a "raised circle" around the perimeter of the head, usually with an "A", "C", or "M" headmarking in the center. The bolt heads were 5/8" across-the-flats and were standard, non-flanged hex head.

These bolts were discontinued by GM quite a few years ago and replaced by bolts with a flanged head and reduced wrenching size.

I believe that Paragon reproduces the original style bolts.

[Ned T.]

Re: 1969 Head Bolts

I just received the set I bought from Paragon yesterday. They have a large "X" in the center of the head and a small "m" in one corner. Is this the correct markings or is it just the best available?

[Joe L.]

Re: 1969 Head Bolts

I just received the set I bought from Paragon yesterday. They have a large "X" in the center of the head and a small "m" in one corner. Is this the correct markings or is it just the best available?

Ned-----


It sounds like you're talking about big block head bolts. The ones I was describing above are for small blocks. From what you describe, the bolts generally sound like correct big block head bolts. Whether they are 100% correct in every nuance, I'm not sure.

[Ned T.]

Re: 1969 Head Bolts

Ned-----


It sounds like you're talking about big block head bolts. The ones I was describing above are for small blocks. From what you describe, the bolts generally sound like correct big block head bolts. Whether they are 100% correct in every nuance, I'm not sure.

Joe, They are for a big block. I was mainly concerned that they at least "look" correct. i would love to know what tensile strenght they are rated at. My engine builder didnt want to reuse the old bolts.

Thanks, Ned

[Joe L.]

Re: 1969 Head Bolts

Joe, They are for a big block. I was mainly concerned that they at least "look" correct. i would love to know what tensile strenght they are rated at. My engine builder didnt want to reuse the old bolts.

Thanks, Ned

Ned-----


Original bolts are ok to re-use as long as they are FIRST RUN (i.e. the engine was assembled at the factory and not disassembled since that time) AND there is absolutely no damage to the shank or threads.

If you compare your original bolts (assuming that they're original) to the reproductions I think you'll find that there is a slight difference. In fact, the "reproductions" might actually be the current GM SERVICE bolts. In that case, you don't need to be concerned, at all, about their conformance to original material grade specs. However, even if they actually are reproductions, I would expect that they're manufactured by a major fastener supplier that observes original specs.

[Ned T.]

Re: 1969 Head Bolts

Joe,

Thanks I'll be stopping by the engine builders on Monday. I want to get a good look at the bolts that came out. The bottom end of the motor had bearings replaced but it's still a standard bore, which was real good news. I was afraid it would be at least 30 over if not 60.

Ned