Headmark on Cylinder Head Bolts

[Douglas L.]

I am in the process of rebuilding my 72, base motor to factory specs. I noticed that there are two cylinder head bolt headmarks available for that year, the "TR" and the "double circle". Does it matter which one I use or does it vary by build month?

[Chuck S.]

Re: Headmark on Cylinder Head Bolts

I am in the process of rebuilding my 72, base motor to factory specs. I noticed that there are two cylinder head bolt headmarks available for that year, the "TR" and the "double circle". Does it matter which one I use or does it vary by build month?

Are these the headmarks that are existing on the head bolts, or did you learn this information from another source? I am unfamiliar with 72 head stamps and can't verify these headstamps as correct for head bolts. What I can say is that TR headstamped fasteners are often sold as replacement bolts in certain year applications for which they were never used originally. In the case of head bolts, I would say that is unlikely, but the first step would be to confirm the correctness of those headstamps. If those are existing on the engine, they are probably original...maybe some 72 experts will clarify.

In general, head marks may not be perfectly uniform in every fastener application on a car. Since fasteners were constantly replenished in the bins near assembly areas, and there were generally several suppliers for any given MY year, it is typical to find more than one fastener head stamp in a given application. To answer your question then, headstamps may be mixed on the same head, different headstamps may be more prevalent from one month to the next, or even change from one car to the next depending on what the assembly worker happened to grab out of the bin.

[Douglas L.]

Re: Headmark on Cylinder Head Bolts

When I removed the existing cylinder head bolts there were no headmarks on them. The engine was "cheesed up" prior to me getting it". I am basically starting from scratch. I have learned that they are either a "TR" or a "double O".

[Chuck S.]

Re: Headmark on Cylinder Head Bolts

When I removed the existing cylinder head bolts there were no headmarks on them. The engine was "cheesed up" prior to me getting it". I am basically starting from scratch. I have learned that they are either a "TR" or a "double O".

On my late 70, I can recall seeing many "Double Circle" headstamps, but if there are ANY TR headstamps, there is likely to be only one TR headstamp on the entire car. This is less relevant to your 72 since contracts to fastener suppliers were likely to change depending on competitive bidding and "spreading the wealth". Patrick Hulst is the guy that can tell you about 72s.

[Jack H.]

Re: Headmark on Cylinder Head Bolts

Headmarks varied based on the luck of the 'draw' from the inventory bins on the assy line at the engine plant(s). As I walk the scrap yards, looking for this/that, I've seen MORE than one original SB or BB engine from the era that appeared untouched with several 'characteristics':

(1) Headmarks on one or both banks randomly mixed with different suppliers' fasteners.

(2) Engines with one bank populated with one headmark and the opposite bank stuffed with another vendor's bolts.

That tells me the cylinder heads were installed at two different work stations, one doing the RH head and the other doing the LH head where their working parts bin(s) were filled/refilled rather randomly... Remember, GM had more than one qualified supplier for most fasteners, but the PN was the same for all and they were mixed in inventory stores at various production facilities.