1970 bumper bolts finish and marking

[Bob B.]

I am finishing up my 70 Convertible 6,787 March 14 build Going for Top Flight. I am looking all over the Tech Manual/Judging guide #5
I think the finish on all bumper and brace bolts are the black oxide on early 70 cars, BUT where does it say that in the manual and / or show head marks ? How much of a deduct is it for Paragon bolts / washers ? BTW the new #5 TIM/Judging Guide is OUTSTANDING great work guys very much appreciated.
Thanks,
Bob #967

[Gary B.]

[Joe L.]

Re: 1970 bumper bolts finish and marking

I am finishing up my 70 Convertible 6,787 March 14 build Going for Top Flight. I am looking all over the Tech Manual/Judging guide #5
I think the finish on all bumper and brace bolts are the black oxide on early 70 cars, BUT where does it say that in the manual and / or show head marks ? How much of a deduct is it for Paragon bolts / washers ? BTW the new #5 TIM/Judging Guide is OUTSTANDING great work guys very much appreciated.
Thanks,
Bob #967

Bob------


There were VERY few bolts on a Corvette that were black-oxide finished. Those that were dark were almost always black or gray (zinc) phosphate, including most of the bumper bolts.

[Edward J.]

Re: 1970 bumper bolts finish and marking

I discovered that also a few days ago also. Another addition for the next manual.

We do describe the braces and bolts in the chassis section. Many of the bolts are the same as those used on the bumpers.

I have seen grade 5 bolts with head markings of C, M, RBW and looked at a 72 a few days ago with TR bolts. I think 70’s were black phosphate, and then during late 71 into 72 a mixture of zinc-plated and black-plated bolts show up. By end of 72, they are pretty much all zinc-plated. That includes the lock washers and very thin flat washers.

I think….. that’s pretty accurate. Maybe Paul Oslanski or Shannon will chime in and set me straight.

Gary Bosselman

Gary, My April 72 where is pretty much black phosphate, with the exception of the outside rear bolts , and where pretty much were all TR bolts.

I also have some pic.s of a 72/ 300 mile ZR1 and the TR bolts were zinc. and washers were blk phosphate. some where these cars may of had the plating switched in 1972 model year, as my 72 had the original bumpers and were not removed that I know of until I restored car.i think also that the bolts and washer were Zinc in 70/71??

[Kenneth B.]

Re: 1970 bumper bolts finish and marking

I discovered that also a few days ago also. Another addition for the next manual.

We do describe the braces and bolts in the chassis section. Many of the bolts are the same as those used on the bumpers.

I have seen grade 5 bolts with head markings of C, M, RBW and looked at a 72 a few days ago with TR bolts. I think 70’s were black phosphate, and then during late 71 into 72 a mixture of zinc-plated and black-plated bolts show up. By end of 72, they are pretty much all zinc-plated. That includes the lock washers and very thin flat washers.

I think….. that’s pretty accurate. Maybe Paul Oslanski or Shannon will chime in and set me straight.

Gary Bosselman

My 70 VIN 7601 has the black phosphate with M & RBW heads on the rear bumper brackets so I would think your right.

[Bob B.]

Re: 1970 bumper bolts finish and marking

My Bad, you are correct black phosphate
Bob

[Bob B.]

Re: 1970 bumper bolts finish and marking

GARY THANKS FOR YOUR REPLY take a look at page 111 on #5 JG Fasteners; "350 cast iron intakes used black -plated hex head bolts without any washers for all years" that is a bit confusing , I think they may have been black but were painted over with the manifold good ol Chev orange, but it doesn't say that confusing. I understand that the intake manifold was painted orange using a crude shield to prevent the valve covers from getting the orange paint when the manifold is painted orange ON the car. My car was VERY original, manifold had never been removed but my photos show that entire area at the base of the intake manifold/head/valve cover being black grease and burnt paint from time but I think the bolts were orange when delivered to the dealer new. AGAIN, #5 is OUTSTANDING,
that one just sent me back to looking at photos before rebuild THANKS BOB #967

[Paul O.]

Re: 1970 bumper bolts finish and marking

From what I have seen over the years it seemed that these bolts and washers. Were a mixed bag 70 tended to be black finish but at some point some silver finishes would appear. That would occur through all 3 years after 70 for sure there was no consistences from one finish or the other. As well as the head markings. For a 70 I would do a black finish as Gary stated plus a mixture of head markings. Make sure you have washers stacked correctly.

[Sal C.]

Re: 1970 bumper bolts finish and marking

My experience on the 1972s anyway is black on the brackets and silver on the chrome. Don't remember seeing silver
bolts on any brackets on 70 or 71 either.