Any 71 BB owners know about ground straps?

[Chuck S.]

Re: Any 71 BB owners know about ground straps?

I got two houses, 5 Corvettes, and everything else I own, that I WILL bet against your IRA as to the use of this ground strap, after it is no longer shown in the AIM books.
Lynn

Lynn, I was only joking...I can't afford to bet my IRA.

But, your membership number is low enough to know that everything you find on old Corvettes is not necessarily genuine original equipment, and determining the difference is tricky. If that has been your approach to research, you're lucky still have your betting shirt.

I can't explain why all those Corvettes you worked on had ground straps after 70, but 70 AIM shows for 70 they were discontinued. It was probably because the body mount bolting design provided bird cage grounding without the need to install an additional cable. It would be unlike GM to go back to an older, more costly design after having made the change, but until someone shows me a later year AIM with the grounding cable sheet, I'm remain unconvinced by memories...especially mine.

[Lynn H.]

Re: Any 71 BB owners know about ground straps?

Lynn, I was only joking...I can't afford to bet my IRA.

But, your membership number is low enough to know that everything you find on old Corvettes is not necessarily genuine original equipment, and determining the difference is tricky. If that has been your approach to research, you're lucky still have your betting shirt.

I can't explain why all those Corvettes you worked on had ground straps after 70, but 70 AIM shows for 70 they were discontinued. It was probably because the body mount bolting design provided bird cage grounding without the need to install an additional cable. It would be unlike GM to go back to an older, more costly design after having made the change, but until someone shows me a later year AIM with the grounding cable sheet, I'm remain unconvinced by memories...especially mine.

Chuck,
I figured you were joking, but would make the bet. I understand fully what your saying about not accepting everything I see (or think I see) as being original, but when it comes to this particular ground strap I have absolutely no doubts as to their use (at least up until my 80 which for sure is unmolested in this area). Birdcages are really my gig, and I have cut apart many, and have NEVER seen one that did not have this strap or evidence of it. The later less desirable (just a term) 70's cars are the ones I have had the most of, so I am as perplexed as anyone as to why it would have been "canceled" or removed from the AIM. This does not seem to be something that was done. I also understand the need of some type of proof for being 100% convinced, I am the same way at times (like being from Missouri-you have to show me). I am certain that if enough members of these mid to late seventies cars chime in that everyone with an original car will have this ground strap there. The only time I would even consider it may NOT be there is possibly in a radio delete car, and I am not certain without looking it up exactly when the radio became standard equipment.
Lynn

[Paul C.]

Re: Any 71 BB owners know about ground straps?

I apologize if I'm alittle dense on this one--but can someone orient me on the picture John H. posted. My 1971 AIM doesn't show it and I can't figure out what I looking at. Thanks Paul

[Lynn H.]

Re: Any 71 BB owners know about ground straps?

Paul,
The picture John shows is of the #1 body mount on the exterior of the frame at about the area of the firewall (directly below), or at the front of the drivers door. Here are a couple of photos I just took from my 80 of the same area and strap. In addition to the braided copper strap, on the 80 there is also another wire grounded to this spot. One other thing about the later versions of this (compared to 70-72) is that instead of the clip with the alligator teeth on one end, both ends are fastened with screws.

After looking at the 1980 AIM, it clearly shows the braided copper ground installed as in the photos below. The "other wire" is the ground for the forward lamp harness. This is depicted on page 511 in the 80 AIM. I do not have any AIM manuals between 72 and the 80 so I would be interested in exactly when this ground "reappeared" in the manuals.

[Chuck S.]

Re: Any 71 BB owners know about ground straps?

...Birdcages are really my gig, and I have cut apart many, and have NEVER seen one that did not have this strap or evidence of it. The later less desirable (just a term) 70's cars are the ones I have had the most of, so I am as perplexed as anyone as to why it would have been "canceled" or removed from the AIM. This does not seem to be something that was done...

Actually, I wasn't the first to post this info for 70s...after I posted, I discovered that Sal had beat me to the punch by a half hour while I was researching and composing.

You don't think I would actually question the accuracy of your recall without actually laying hands on the AIM pages, do you? GM might have gone back to the cable after redesigning the body mount bolting...I can only show you what I know for a late 70.

When I took this car apart, I beat my head against the wall trying to reconcile vendor offerings with what I had actually found on the car...there were no ground cables, or any evidence there had ever been any. After finding the AIM pages, I concluded that vendors will sell anything you'll buy, and that the ground cables myth, at least for late 70s, was BUSTED.

I started to scan the AIM sheets in as thumbnails so you could read the word "canceled", but somehow I'm thinking you would remain unconvinced. I have only one more comment...if Paul decides to put a ground cable his 71 (less than one year after apparent discontinuation in 70) based on a photograph of your 80, and after not finding that sheet in his 71 AIM...well, Paul, I got some oil leases in downtown Houston that I want to sell ya.

[Lynn H.]

Re: Any 71 BB owners know about ground straps?

Chuck,
I see how these things can get argumentative, but that is NOT my intention, but...
You are right about me NOT being convinced. You seem to be discounting Terry's post about the strap being on his early car. I know for a fact it was on my mid May built 70, I just looked at the part I removed (also on my 72). I also just looked at 3 different birdcages (in my garage) that are out of the cars that all show evidence of the strap. One in particular is from a 76 which had the strap attached with the screws at both ends. I am including a photo of that birdcage in that area. I also had 2-73's and 1-74 that I KNOW all had the ground strap. This would only leave a short period that I cannot personally account for. I agree with you whole heartedly, that this information SHOULD be in the AIM. I cannot offer any reason why it was not. I do know that I have had my 72 long before anybody was thinking of restoring them, so the idea of someone adding this on at a later date is not even in the equation. I am sure someone has the answer to this, the question is who.....
Lynn

[Paul O.]

Re: Any 71 BB owners know about ground straps?

Just adding some info the body mounts usually will give you a ground for the electrical system but its not a 100%. 73 and later body mounts used rubber spacers and I would expect that strap to be there but I would still expect it to be on 71 and 72 also. The ground strap at the #1 mount would give the birdcage and the frame a normal ground for all the interior electrical items. Plus prevent static build-up between the body and frame.

Now I am going off of memory which can be bad I believe my 71 and my friends both had the ground strap one Sept 70 and other Jan 71 builds. But there should be tell tail signs if the ground was ever there. Like a screw hole on the frame mount and the body mount bracket. Paul 18046

[Bill C.]

Re: Any 71 BB owners know about ground straps?

Hey --


There was never a strap placed on my 72. There is no hole in the mount/frame. I pulled the body off my frame for the 1st time, it had only 45K miles on it, no evidence of a ground strap at all.

Is 72 a year where it may have not been installed?

[Graeme B.]

Re: Any 71 BB owners know about ground straps?

If the hole in the body mount is threaded,it had the earth strap. Graeme.

[Paul C.]

Re: Any 71 BB owners know about ground straps?

Just got done crawling around under the car--it's cold!!!!. The car was undercoated and there is no ground strap however there is a hold the frame where John's picture showed it was attached. I can not tell if the hole is threaded because of the undercoating. I don't see where the clip was attached. If there was one why would someone remove it? For judging purposes I guess I will have to install one. Maybe they were hit and miss on the line???Thanks Paul

[Terry M.]

Re: Any 71 BB owners know about ground straps?

Chuck,
I see how these things can get argumentative, but that is NOT my intention, but...
You are right about me NOT being convinced. You seem to be discounting Terry's post about the strap being on his early car. I know for a fact it was on my mid May built 70, I just looked at the part I removed (also on my 72). I also just looked at 3 different birdcages (in my garage) that are out of the cars that all show evidence of the strap. One in particular is from a 76 which had the strap attached with the screws at both ends. I am including a photo of that birdcage in that area. I also had 2-73's and 1-74 that I KNOW all had the ground strap. This would only leave a short period that I cannot personally account for. I agree with you whole heartedly, that this information SHOULD be in the AIM. I cannot offer any reason why it was not. I do know that I have had my 72 long before anybody was thinking of restoring them, so the idea of someone adding this on at a later date is not even in the equation. I am sure someone has the answer to this, the question is who.....
Lynn

My 1970 has A29 (January 29, 1970) on the trim tag. Given the 1/9/70 date on the Engineering Change Request I am not sure that my car tells us anything much. WTH mine has a capacitor on the TI coil.

However I am of the opinion they all got that ground strap, or should have got it. I think that page was cancelled because the strap was installed someplace else on the production line, and someone decided it had nothing to do with a radio or no radio. I just can't prove that opinion. And Paul's point about the rubber body mounts is a good one.

[Terry M.]

Re: Any 71 BB owners know about ground straps?

Just got done crawling around under the car--it's cold!!!!. The car was undercoated and there is no ground strap however there is a hold the frame where John's picture showed it was attached. I can not tell if the hole is threaded because of the undercoating. I don't see where the clip was attached. If there was one why would someone remove it? For judging purposes I guess I will have to install one. Maybe they were hit and miss on the line???Thanks Paul

Paul, If there are really no signs of one having been installed -- stick to your guns, and don't do it. My guess is most judges will not notice it is missing anyway.

[Dave S.]

Re: Any 71 BB owners know about ground straps?

My 1970 has A29 (January 29, 1970) on the trim tag. Given the 1/9/70 date on the Engineering Change Request I am not sure that my car tells us anything much. WTH mine has a capacitor on the TI coil.

However I am of the opinion they all got that ground strap, or should have got it. I think that page was cancelled because the strap was installed someplace else on the production line, and someone decided it had nothing to do with a radio or no radio. I just can't prove that opinion. And Paul's point about the rubber body mounts is a good one.

I just checked my 71 #21467. It is a radio equiped car. No ground straps but there are pilot holes in the bracket welded to the frame. No evidence of a ground strap ever being installed. I'll check 71 #16798 tomorrow.

[Lynn H.]

Re: Any 71 BB owners know about ground straps?

My 1970 has A29 (January 29, 1970) on the trim tag. Given the 1/9/70 date on the Engineering Change Request I am not sure that my car tells us anything much. WTH mine has a capacitor on the TI coil.

However I am of the opinion they all got that ground strap, or should have got it. I think that page was cancelled because the strap was installed someplace else on the production line, and someone decided it had nothing to do with a radio or no radio. I just can't prove that opinion. And Paul's point about the rubber body mounts is a good one.

I want to agree with Terry's' beliefs, as after a little more digging I have come up with the following from my parts books:
The part number for the ground strap in the 69 AIM is 2982782
The listing in my 53-77 parts book shows:
GR-9.663 P/N 2972627 63-71 Corvette-STRAP,body bracket ground (replaces P/N 2982782)
The part number for the ground strap in the 80 AIM is 6290663 (pg.84)
The listing in my 53-77 parts book shows:
GR-9.663 P/N 6290663 73-76 Corvette-STRAP,door sill reinforcement ground
This only leaves 72 in question, and possibly 78 (if any year is actually in question), as in one of my parts and illustration manuals it shows the 6290663 for 79-82. I believe the part number change to 6290663 is when the strap changed from the one with the clip with the alligator teeth, and one eyelet, to the strap that had two eyelets and was fastened with the self tapping screws at both ends. In some of the postings that mentioned holes with possibly no threads, I am guessing that if the car never had the strap there would be no threads, as all the screws I have seen for this application have been of the self tapping variety. While this proves nothing beyond a doubt, I think it does give some more insight as to the use and application of a ground strap in this location.
Lynn

[Dave S.]

Re: Any 71 BB owners know about ground straps?

I want to agree with Terry's' beliefs, as after a little more digging I have come up with the following from my parts books:
The part number for the ground strap in the 69 AIM is 2982782
The listing in my 53-77 parts book shows:
GR-9.663 P/N 2972627 63-71 Corvette-STRAP,body bracket ground (replaces P/N 2982782)
The part number for the ground strap in the 80 AIM is 6290663 (pg.84)
The listing in my 53-77 parts book shows:
GR-9.663 P/N 6290663 73-76 Corvette-STRAP,door sill reinforcement ground
This only leaves 72 in question, and possibly 78 (if any year is actually in question), as in one of my parts and illustration manuals it shows the 6290663 for 79-82. I believe the part number change to 6290663 is when the strap changed from the one with the clip with the alligator teeth, and one eyelet, to the strap that had two eyelets and was fastened with the self tapping screws at both ends. In some of the postings that mentioned holes with possibly no threads, I am guessing that if the car never had the strap there would be no threads, as all the screws I have seen for this application have been of the self tapping variety. While this proves nothing beyond a doubt, I think it does give some more insight as to the use and application of a ground strap in this location.
Lynn

As a follow up to yesterdays post I checked my 71 #16798 which is radio equiped. No ground strap(s) on the front body mount(s). There is a 3/16" pilot hole on the front flange of the frame bracket. No pilot hole in the passenger side frame bracket. 71 #21467 is exactly the same.