bolt finishes for a '70 chassis / suspension

[Steve G.]

Re: bolt finishes for a '70 chassis / suspension

Thanks for clarification. Mine is an automatic, and the bolts do appear dark. I'll leave them alone and will not plate them.

Any idea what the finish is supposed to be on the long bolts that go to radiator support (auto, BB, with ac)? The bolts have gear shaped, external tooth lock washers. The bolts have a light gray finish on them that I assume is original.

[Joe L.]

Re: bolt finishes for a '70 chassis / suspension

Thanks for clarification. Mine is an automatic, and the bolts do appear dark. I'll leave them alone and will not plate them.

Any idea what the finish is supposed to be on the long bolts that go to radiator support (auto, BB, with ac)? The bolts have gear shaped, external tooth lock washers. The bolts have a light gray finish on them that I assume is original.

Steve------


My recollection is that the bolts were zinc plated. However, it is possible that one or more of them were not. There were 3 different bolts used for the 4 positions.

[Steve G.]

Re: bolt finishes for a '70 chassis / suspension

Thanks Joe and all. This has been very helpful. Applicable bolts are going to plater for zinc plating. He is doing zinc plating with chromate (gold) afterplate on the front caliper bracket. And all four dust shields are getting white (cad) plating. I'll be doing the rest of my h/w with either clear lacquer (for 'natural' finish) or black phosfate with the kit I got from Palmetto. Steve

[Edward J.]

Re: bolt finishes for a '70 chassis / suspension

Edward-----

Are you saying that your 72 is an automatic transmission? The bolts were different for auto versus manual transmission. Auto transmission used a standard hex head bolt of 3/8-16 X 1-3/8" and of GM #179842. This bolt was GM 280M material grade (SAE grade 5; 3 lines) and it was of "plain" finish ("plain" finish may appear dark brown or black). These bolts were installed at St. Louis.

Manual transmission bellhousing-to-block bolts were FLANGED hex head and of 3/8-16 X 1-1/4". These were also of GM 280M material grade. All that I have seen were zinc plated. These bolts were installed at the engine plants and not at the vehicle assembly plants.

Joe, was not stating the bolts were different, but the finish on my 72 thm 400, the bolts were a black phosphate or blk. oxide?

[Steve G.]

Re: bolt finishes for a '70 chassis / suspension

I picked up my hardware from plater yesterday - everything looks great! I had a couple hundred peices plated, and I believe I got them all back except for one body mount shim. And one bell housing mounting bolt. However I got one 'extra' bolt back that is same thread pitch as the missing bell housing mounting bolt. I am wondering if one of the 6 bell housing bolts may have been different than the other 5? My car is a BB automatic. Is it possible the one bolt that mounts the battery cable clamp to the bell housing could be slightly shorter (I would have thought it would be longer if it were different) than the others? Does anyone have similar car and crazy enough to know these details?

I have 5 bolts that are, 1 3/8" long (not including head) x 3/8", 16 threads/inch. Threads stop about 1/4" before head. Bolts are mixture of 'A' and 'RSC' heads.

The 'extra' bolt - am hoping its the missing '6th' bolt - is 1 1/16" long, same pitch, threaded all the way to head. Head marking is 'L5'.

Steve

[Joe L.]

Re: bolt finishes for a '70 chassis / suspension

I picked up my hardware from plater yesterday - everything looks great! I had a couple hundred peices plated, and I believe I got them all back except for one body mount shim. And one bell housing mounting bolt. However I got one 'extra' bolt back that is same thread pitch as the missing bell housing mounting bolt. I am wondering if one of the 6 bell housing bolts may have been different than the other 5? My car is a BB automatic. Is it possible the one bolt that mounts the battery cable clamp to the bell housing could be slightly shorter (I would have thought it would be longer if it were different) than the others? Does anyone have similar car and crazy enough to know these details?

I have 5 bolts that are, 1 3/8" long (not including head) x 3/8", 16 threads/inch. Threads stop about 1/4" before head. Bolts are mixture of 'A' and 'RSC' heads.

The 'extra' bolt - am hoping its the missing '6th' bolt - is 1 1/16" long, same pitch, threaded all the way to head. Head marking is 'L5'.

Steve

Steve------


Are all of the bolts flanged head style?

[Steve G.]

Re: bolt finishes for a '70 chassis / suspension

None of the bolts have flanged heads Joe. They are standard hex head style. This is an automatic car. Bolts were 'black'. Should any of them be flanged style? Steve

[Joe L.]

Re: bolt finishes for a '70 chassis / suspension

None of the bolts have flanged heads Joe. They are standard hex head style. This is an automatic car. Bolts were 'black'. Should any of them be flanged style? Steve

Steve------


OK, I was thinking it was 4 speed. You used the term "bellhousing bolt" at one point in your post and I guess I "keyed" on that as meaning a manual trans bellhousing. However, reading your post again I see that you clearly stated that the car is an automatic.

In any event, the bolts used for the automatic transmission-to-block were standard hex head and not flanged. For an automatic transmission the part that we think of as a "bellhousing" for a manual transmission application is not a bellhousing, at all, but just part of the transmission CASE.

Actually, I don't know why standard hex bolts were used for the automatic trans-to-block application. The flanged head bolts were just as appropriate for these fasteners as for the manual transmission bellhousing. The bolts on manual versus automatic trans were installed at different places (engine plants versus assembly plants) but that does not mean that flanged head bolts could not have been used.

[Steve G.]

Re: bolt finishes for a '70 chassis / suspension

Thanks for the clarification Joe. I assume the sixth bolt that captured the battery cable clamp was supposed to be different than the other five. Unfortunately, I did not notice it before I brought them to the plater.

I'm very happy I with the results. I had bolts that had previous signs of zinc re-plated. And the front disc backing plates zinc plated with light gold chromate overwash (they look a bit too gold to me, though plater indicated I could hit them with steel wool or scotch bright to remove some gold). See picture attached. I started doing the black phosfate process on other bolts myself yesterday. Those are coming out very nice. Pretty easy except for the oiling wiping, oiling...

Steve

[Terry M.]

Re: bolt finishes for a '70 chassis / suspension

Thanks for the clarification Joe. I assume the sixth bolt that captured the battery cable clamp was supposed to be different than the other five. Unfortunately, I did not notice it before I brought them to the plater.

I'm very happy I with the results. I had bolts that had previous signs of zinc re-plated. And the front disc backing plates zinc plated with light gold chromate overwash (they look a bit too gold to me, though plater indicated I could hit them with steel wool or scotch bright to remove some gold). See picture attached. I started doing the black phosfate process on other bolts myself yesterday. Those are coming out very nice. Pretty easy except for the oiling wiping, oiling...

Steve

I can't say that I have ever seen an original 1968-1972 brake dust shield that was gold tone. The SERVICE REPLACEMENTS for many years were gold tone, but not the originals for early C3s.

[Steve G.]

Re: bolt finishes for a '70 chassis / suspension

Terry, I had the dust sheilds done in white zinc. I had the front backing plates (may not be the correct term for them - these are the thick plates that the calipers bolt to) done with zinc, then a gold overwash. Steve

[Paul O.]

Re: bolt finishes for a '70 chassis / suspension

Steve the Brake Caliper mount brackets in your photo are the correct color. A gold wash when Judging Chassis that is what we are looking for. But the dust shields are not a gold shade the fronts silver, rears a galvanized look as Terry stated earlier. Paul 18046

[Terry M.]

Re: bolt finishes for a '70 chassis / suspension

Steve the Brake Caliper mount brackets in your photo are the correct color. A gold wash when Judging Chassis that is what we are looking for. But the dust shields are not a gold shade the fronts silver, rears a galvanized look as Terry stated earlier. Paul 18046

It always helps to be talking about the same parts. Now where did I put that thingamajig?