Bolt Size for #4 Body Mount
Can anyone tell me the bolt size for the #4 Body Mount for a 63 convertible? I've looked in the AIM and the Part # it states is #3797244. I cannot find the in the parts index book that I have.
Thanks
Thanks
-
-
-
Re: Bolt Size for #4 Body Mount
Thanks Gary!Comment
-
Re: Bolt Size for #4 Body Mount
Gerald------
GM #3797244 was never available in SERVICE from GM. The part number implies that it was, in some way, a special bolt. However, its apparent description sounds more like a "standard parts" bolt. It might be that it had a non-standard thread length based on its total length.In Appreciation of John HinckleyComment
-
Re: Bolt Size for #4 Body Mount
I think the body mount bolts are pointed to help them center a caged nut. Is that special enough to get them promoted from the standard parts category?Comment
-
Re: Bolt Size for #4 Body Mount
Patrick,
They are indeed pointed, exactly for the reason you state.
GaryComment
-
Re: Bolt Size for #4 Body Mount
Jerry, I'm going to ask a loaded question.....
Why do you need these bolts?
If it's because they are badly rusted at the cage square nuts under the decklid hinge supports, you have a tedious exercise to replace them ahead. The #4 frame underbody mounts may need attention too.
Please share some photos of the square nut cage areas along with underbody #4 mounts, so we can advise you on the upcoming task to replace those bolts.
Getting at the outer bolts at the top of the hinge supports is very difficult to access and threaded into a nut plate welded into the horizontal steel drain gutter reinforcement. These may be a bear to remove due to rust, and if broken, will be even worse.
It can be a lot of work once you get in there. I've done many of these and just want you to be aware of the difficulty level if you're going in there to replace 2 bolts. It can turn into a major task.
RichComment
-
Re: Bolt Size for #4 Body Mount
Gerald,
Bolt #3797244 is indeed a pointed bolt but it's the shorter body mount bolt that measures 7/16-14 x 1-9/16" grade 5 in zinc. I'm not well versed in '63 AIM knowledge but the '65 and '66 AIMs both call for bolt #3797244 at the convertible body mount #2 (UPC 1 ASM sheet G3) and this same bolt is also found at the front frame fork mount to radiator support lower cage nut (UPC 11-13 sheet A5).
Gary is correct in that the '65-'66 #4 body mounts call for the longer 2-1/2"bolt.
Happy hunting,
MikeComment
-
Re: Bolt Size for #4 Body Mount
Mike-------
Apparently, GM did not consider the 3797244 necessary in SERVICE for the application and that's probably why it was a PRODUCTION-only piece. For SERVICE, bolts from the standard parts catalog could be used. Generally, pointed tip bolts are a PRODUCTION convenience. They were not available from GM as standard parts items (except for tapping bolts) and can be difficult to find from industrial/commercial fastener suppliers.
Other C2 body mount bolts, GM #3872931, GM #3902232, and GM #3772263 were not available in SERVICE, either.In Appreciation of John HinckleyComment
-
Re: Bolt Size for #4 Body Mount
To complete the documentation, how long is GM 3872931, which is the #1 body mount bolt near the firewall?
GaryComment
-
Re: Bolt Size for #4 Body Mount
Okay guys,
The bolt is 7/16-14 and is 2" long with a point. The first one I attempted broke right at the end! the second one just spun in the cage. The hinges came out very easily as they were not rusted at all. The second nut I got out by using a Dremel tool with a cutter on it so I split the nut in half and the bolt fell out on the floor. So my problem is solved. I didn't remember the last time my body flexed like that. While the hinges were out, I replaced both springs. It was a relatively easy job. One was broken anyway, so I used the process I found somewhere where I would put the spring on a floor jack and spread it to the approximate correct length. Then I put wooden wedges between the coils and then released the jack. I then slipped the expanded spring onto the hinge and removed the wedges. I took the other hinge off the same way with the wooden wedges. All good to go now.
Thanks everyone for your comments.Comment
-
Re: Bolt Size for #4 Body Mount
Jerry, I surmised you needed the bolts for that reason. Glad you didn't have too much trouble. Good work.
For those with rusted mounts, hinge supports, #4 bolts/cage nuts, etc, see the following for a variation of the processes on a 1966 I did years ago.
Here Post#26
Here Post#27
Here Post#28Comment
-
-
Re: Bolt Size for #4 Body Mount
Hi Gary,
I've been away from my original '65-'66 hardware and cars for a few months now. The dimensions that I posted were from an archived source that I trust but it was wrong this time. Sorry for this error. You are correct in your measurement of 1-3/4" inch long. I just spoke with a good friend/bolt guru and he assured me that the front frame fork to radiator support cage nut bolts are 1-3/4" inches long, grade 5, zinc and usually "RBW" head marked. Measured to the tip. Personally, I've never seen any other head mark there but "RBW." Your pictured bolt here is in really nice shape. Hard to find this particular bolt in that shape.
I'd be interested to see measurements posted here from the parts experts that have access to these GM dimensions. My GM Engineering Standards manuals provide no information for GM hardware with part numbers beginning with "3" such as #3797244 bolts.
MikeComment
Comment