1970-72 GS/Skylark Body Mounts
Another area of concern with restorations is body mounts. The kits and prices are all over the map, and despite some investigation, I still can't determine who makes what and who sells which!LOL Here is a picture of one of my original mounts:
This mount was one of the forward cowl mounts (#1 position), which is why it has a nut on top and doesn't just thread into the body as on the #3, #6, and #7 positions. #1 and #2 have a nut, and # 4 and #5 are solid. Obviously, these are not reusable! Its interesting that the mount core seems to have rusted from the center out and the area near the body(and including the body itself) is ok. Also note the small metal ring (now separated) that is molded into the lower part of the upper mounts, repro mounts do not have these. The lower insulators were yellow from the factory, you can still see the paint. The bolt itself was corroded to HALF its original diameter in the shank (it is hidden in this picture), reason alone to change the hardware on any old car.
I ordered a body mount kit from a local supplier for a 72 Chevelle convertible. Being an A-body, all the GM products are the same, although I have heard rumours that the GTO and 442 kits are different somehow. Anyway, the kit was fairly inexpensive and I guess you get what you pay for. It included the rad support mounts, the solid mounts for #4 and #5 position, and the rest of the two piece mounts (including two slightly different ones for the #7 position). Note that ALL Buick A-bodies had the extra mount in the cowl area, so if you are building a GS hardtop you still need to order the convertible kit to get the extra mount (Chevy cars only had that mount on convertibles).
Here are the body mounts from the kit:
As you can see, the solid mounts look ok but the center part that sits in the frame is slightly off. Not a big deal as the body simply sits on top of these. The #7 very aft mount (on the RH side) is smaller diameter, yet slightly taller, with more rubber between metal center piece and the edge of the frame hole area where it rests. The main mounts (LH side of this pic) seem quite solid with hard rubber, a metal flange on the top side that covers the entire rubber part, and a fairly wide hole for the bolt to pass through, with less rubber between it and the frame edge when installed. The two lower pieces are the insulators which get crushed between the bolt head/washer and the frame, helping to hold the mounts in position.
About this time, there was a discussion about body mounts and it came to light that the upper body mount was still available from GM, but you could no longer get the insulator (lower rubber piece). I had tried to order these about 1 year ago and they were no longer available.....when someone told me they just bought a set I called my GM parts guy and sure enough you could get them again (go figure).
Here you can see the two side by side. The GM mount appears slightly softer, and slightly thicker as well. A much better produced part. The center piece protrudes further through the mount than the repro style.
Upper mount GM p/n 1242761 as per the GM Parts Book:
68-71 #6 and #7 positions
68-71 (446 series) #1 and #2 positions
68-71 (all) #3 position
70-71 #1 and #2 positions (all excluding 446 series)
72 #3, #6 and #7, sheetmetal (rad support) positions
Just a note here. 68 and 69 446 models are the 400 powered GS, in 1970 the 446 model was the 455 powered GS. In 71 and 72 the big block powered cars had different ID so that does not apply, even though the GM parts book still lists the code and seems to have a conflict. Original GS models had a different p/n mount in the #1 and #2 locations, although looking at several cars that have been apart this did not always seem to be followed. They were probably a different hardness of rubber.
Since 71 and 72 frames are basically the same, this p/n applies to every bolt in mount position on the car even though original had slightly different mounts at various locations. While the repro kits are helpful and needed, the GM part is definitely superior, and you will pay the same for 12 of the GM upper mounts as you pay for the entire repro kit. By the way, don't waste your money on the hardware kits. Just match up your old bolts to some new grade 8 hardware at any bolt store and get washers that cover the whole diameter of the insulators and save yourself a pile of money, as the hardware kit supplied with my mounts was simply hardware style bolts and washers.
My 1971 assembly manual shows the same mounts at the #1, 2, 6, 7 and sheetmetal (rad support) positions. The #3 might have been a different compound, but as you can see from the GM parts book this same p/n was also acceptable for the #3 position. #4 and #5 are the solid type.
April 25, 2003
*I have decided to use the lower insulator for mid 80's GM cars (P/N 457915). This insulator is 7/8" thick and firm rubber. The inside diameter matches the mating steel core of the upper mount, and allowing for the frame thickness will have 1/4" of crush before the steel core contacts the molded in washer of the insulator. This should be about right to get the proper torque values and grip. No way to know for sure until I try to torque them up and see what happens. I will advise at that point.
Well!! After all this time, I stumbled across reproduction lower insulators. They are made by Steele Rubber, who do many types of rubber products. They are a new product and identical in measurement to the lower GM insulator including molded in washer and indeed, their ad on the part says replaces GM p/n 1377367 which is the lower insulator (now discontinued) for every bolt in position in these cars. I have ordered a set and will update this once they arrive and I can inspect them, they are pricey at $9.40 US each but the GM lowers aren't cheap either...Steele rubber P/N is 70-2165-48. If they are good quality it will end all the problems here, as they will look, fit and function the same as GM. Pics will be posted once they arrive.
Now all I need is a source for the solid rubber mounts that the body sits on. Someone must sell them individually. Might have to go used if I can't find a source.
I returned my repro set, and was told they had switched vendors. I would too!!
I am also debating putting the bolt in mount in the #4 position, although GM originally used just the solid type mount for the GS cars. They moved things around to help with ride or performance, Chevy A-bodies apparently had a solid type at #3 and #5 but used a bolt in at #4 to help with axle control on hard acceleration. All the GS cars I have seen have the bolt in body nut in the #4 position even though they were not used. Simple matter to add another bolt in mount, this would tighten up the chassis some I think. #5 on all cars is a solid type mount, no bolt provisions available.
Feb 8, 2004
Steele Rubber lower insulators showed up today. They are a dead match for the original GM 1377367 except for the small vertical ribs the GM ones had. The lower washer is molded in and is correct thickness. Original seems softer, but also has 30+ years of use on it. Note the yellow "code" paint on the original, and the molded in washer that has seperated.
The odd part is that the mid 80's mount, while still having the center hole of the correct diameter for the metal part protruding from the upper mount, is wider overall and may actually give more support. But this is a restoration so the correct style lowers will be used. New GM 1242761(upper) on the left, steele rubber 70-2165-48 (lower) in the middle, mids 80's GM 457915 (lower) on the right.
Feb 27, 2004
How it all ended up: I used the GM 1242761 in every bolt in position in the car. Rad support, #1, #2, #3, #4 (originally solid style), #6 and #7. They all got the GM 457915 lower insulators as well. In the #5 position, I used GM 488610 solid mounts. It all worked out very nice. The Steel Rubber lowers will get used one day along with a set of NOS uppers in the Stage 1 when I go through it again.
May 5, 2005
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