I posted a question last week about my 69 frame extensions. I have both NOS extensions (3958797 & 798) they are the same as what is on my car. The problem I am having is when they are bolted in they are about 2 inches short of the core support mounts. All holes bolt to the frame perfect. I have looked at 2 early 1970 cars and and the bracket is about 2 inchs longer. I was told that 69 - 71 should be the same. Are they? The only thing I can figure is these are the wrong brackets even though that is what my October of 69 GM parts book lists. Any suggestions? Thanks Brad
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Re: 69 frame extensions revisited
Also the 70 brackets stick out about 2 inches past the end of the angled bumper brackets. Mine are pretty much flush on the rear. -
Got AIM?...
The brackets are correct...those part numbers are in my 70 AIM, and I checked them before I answered your last post. They are all the same part number from 68-72 per the parts book.
If you have the 69 AIM, take a look around UPC14, Sheet A2 and UPC14, Sheet A3. Those drawings should help you understand the relationsip of the frame extensions to the front cross member and radiator support, and to the bumper brackets. The radiator support is bolted to the body inner fenders with three self tapping bolts on each side...the bottom of the radiator support is then bolted to the front cross member by two large bolts (7/16"?) inserted through the bottom of the cross member.
Look inside the front of the wheel wells...there should be a long reinforcement riveted into each wheel well that extends from the bottom skirt to the top of the wheel well. The hood hinge bolts screw into weld nuts on the top surface of these reinforcements, and the three radiator support bolts screw into weld nuts distributed equally along the reinforcement's length.
If your radiator support is correctly bolted into those reinforcements...and the bottom radiator support holes are two inches short of aligning with the two holes in the front cross member...and the frame extensions are attached to the correct bolt holes in the frame: then I can only conclude that when the front end was replaced, it was somehow located two inches too far forward. If they used a correct 68-69 front end, I have no idea WHAT they would have done with the two inch gap they would have been left with at the doors, hood etc...fiberglassed it over?
Take a real hard look at UPC14, Sheet A2 to make sure you have those frame extension bolts in the right holes...if they are installed correctly, you have a dilema.Comment
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Nomenclature...
We're beginning to use some terminology interchangeably, and inevitably it's going to add to the confusion...in my previous post I meant that the FRAME EXTENSIONS are all the same from 68-82, and that the parts numbers you posted earlier are correct. There are NO OTHER longer or shorter parts to be tried.
From Joe and Sal's responses to your 2 November post, I learned that the 68-early 69 core supports are attached differently than the later 69 through 72. The 68/early 69 are attached to the frame rather than the front cross member like later 69 through 72...Which core support method are you trying to utilize? If the replaced front end was from a 68, the core support is likely for a 68 as well.
Aside from bolting the 68 core support to the frame rather than the front cross member (69-72), the part differences (brackets, extensions, reinforcements) between 68-69 and 70-72 are primarily related to front bumper installation.Comment
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Re: Got AIM?...
Chuck, first thing is to thank you for your help.I have looked at the AIM and that just confirms that without modification there is only one way for these extensions to bolt to the frame. The bolts on my frame and extensions line up perfect. The extensions that are on my car now are slid forward ( by torch slotting) so that the rear bolt hole in the extension doesn't even come close to the hole in the frame when the extension is bolted to the core support. The core support is bolted correctly to the body.The hood and cowl grille all fit. So I don't think it is a problem with the front end. Like I said yesterday both of the unmolested 70's ( one is original owner ) I looked at the extension is about 2 inches longer between the frame holes and the core support holes . Which makes me think there might be a differance in the production part and the service part. I think that when my front end was replaced they replaced the extensions with service parts.I think I need to find a pair of original extensions to measure to confirm my thoughts. Yuor right I have a Dilema.Comment
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OK, Stand By...
To put a stake in this vampire's heart one way or the other.
Measure the distance from the centerline of most forward hole IN THE FRAME, to the centerline of the bottom hole in the long reinforcement in the front of the wheel well...mine is 7 1/4". If yours is 9 1/4", you have a big problem.
I would bet my life there is no difference in production and service frame extensions...the part numbers are the same; if GM made a change of that magnitude, then the part number would have changed. Not to mention none of the service parts would fit existing cars, and they would be worthless.Comment
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Re: OK, Stand By...
Chuck, I'm at about 8 inches. Now can you measure your extension from the rear upper corner to the bottom front corner ( daigonal). The NOS is 13 1/2. Once again I REALLY appreciate your help.Comment
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Re: OK, Stand By...
About 13 1/2"...to be ultra precise 13 9/16" plus or minus 1/16". I did notice that one of them has elongated mounting holes made by using a smaller diameter hole punch on the rear side of the mounting holes...definitely a factory alteration (not at the assembly plant; this would have been at the supplier's plant maybe at GM's direction). That would work toward moving the frame extension forward.
Based on your measurement, I conclude that the front end was not positioned perfectly. Maybe three quarters of an inch is not a large error in that process when you're up to your arse in curing bonding adhesive, but the body gaps would have to be distributed out and probably remedied with resin and mat. As far as matching those two bottom holes in the core support, 3/4" is the same as 2"...not going to happen.
All those mounting holes are large with a fair amount of slop in them, but not 2" worth. Your best bet is to use the extreme positioning of the bolts in every hole to get the assembly as close as possible. You may still have to elongate the holes in the frame extensions to make it all work out, but there are some large diameter special locking washers on those extensions that may cover the hole elongations. Removing the front clip and properly positioning it for the holes to line up is not an option, and that's what Bubba thought just before he lit up the cutting torch.Comment
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Chuck, Thanks Again *NM*
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