Best source for 69 L-68 intake bolts?

[Patrick N.]

Re: Best source for 69 L-68 intake bolts?

Thanks Grant-that helps a lot! My march L68 has all FP fasteners. For now I have A markings on there but plan to refinish the FP's and put back on. Any idea on finish for the FP, with a light brushing the ones I have look to be natural finish??
thanks again!

[Joe L.]

Re: Best source for 69 L-68 intake bolts?

Thanks Grant-that helps a lot! My march L68 has all FP fasteners. For now I have A markings on there but plan to refinish the FP's and put back on. Any idea on finish for the FP, with a light brushing the ones I have look to be natural finish??
thanks again!

Patrick-----

"A" was a common headmarking for big block intake manifold bolts of the period so I would not be so quick to conclude that you have the "wrong" bolts.

It's like this: all of the 1-1/4" long big block intake manifold bolts of the period were GM #3828782. However, they are not all configured the same. Apparently, there was some "leeway" allowed within the specs for this bolt and different manufacturers made them different ways. All are GM 280M material grade (i.e. SAE grade 5 with 3 lines) and all have about a 1/4" un-threaded shank. However, there are other configuration differences. Some have untrimmed (i.e. "indented") heads with a "thin" flange. Some have trimmed (i.e. "non-indented") heads with a "thick" flange. Some are phosphate-finished and some are zinc finished. Of the ones I've observed, the zinc finished examples usually have the trimmed head with "thick" flange but there may very well be zinc-finished bolts of the other head configuration. The zinc finished bolts were generally used for applications with aluminum intake manifolds.

Bolts which also retained some bracket were usually longer and were not flanged head.

So, how do you know what EXACT bolts were originally installed on any particular engine? The only way to know is to have the known-original bolts for that engine. Otherwise, any bolt of "typical factory production" is as close as you can get. Period.

[Floyd B.]

Re: Best source for 69 L-68 intake bolts?

Patrick-----

"A" was a common headmarking for big block intake manifold bolts of the period so I would not be so quick to conclude that you have the "wrong" bolts.

...

So, how do you know what EXACT bolts were originally installed on any particular engine? The only way to know is to have the known-original bolts for that engine. Otherwise, any bolt of "typical factory production" is as close as you can get. Period.

Great post. I think claims of exacting precision in fastener use on mass production vehicles is a myth and flies in the face of everything we know about production practices in the 1960's. Automobile manufacturers would use any bolt that; a) met the requirements and b) was readily available. If your intake currently has bolts that were commonly used during the period your car was assembled, then I think it is safe to assume they are the original bolts. The burden of proof will be on the judge to prove otherwise.