Bolt Size for #4 Body Mount

[Richard M.]

Re: Bolt Size for #4 Body Mount

Looking at my photos in that earlier post, geesh that frame looked ugly. I remember the guy that sold the car to my friend said to him something like..... "The chassis is just as nice as the body of the car." Don't think so.

I forgot how many hours I put into that frame. Fun to see Before & After.

After
P1070007.jpg

P1070009.jpg

[Bob J.]

Re: Bolt Size for #4 Body Mount

GARY, If possible, I'd like to get the washer measurements for all the washers.
The bolts I pretty much figured out but not the washer sizes.
Take care,Bob

[Bob J.]

Re: Bolt Size for #4 Body Mount

Sure Bob, I've a a date back in the shop tomorrow so I'll get the ruler and caliper out then. I'll get OD, ID, and thicknesses.

Rich

Thank You, Bob

[Gary B.]

Re: Bolt Size for #4 Body Mount

Bob,

The two sizes of plain washers stored with the body mount bolts from my ‘66 have the following dimensions:

Large: OD=1.90”; ID=0.434”; th=0.12”

Small: OD=1.125”; ID=0.46”; th=0.12”

(I wouldn’t trust the 2nd number after the decimal point because of rust.)

Those are very close to the specs for GM 3760866 (large) and GM 3790768 (small) that are called out in the ‘66 AIM. But ‘67, or ‘63-‘65, might be different since at least one of the AIM part numbers for one washer is different for some C2 years. We’ll see what Rich comes up with for ‘67.

Gary

[Bob J.]

Re: Bolt Size for #4 Body Mount

Thanks, Gary
Those numbers are just what I needed.

[Richard M.]

Re: Bolt Size for #4 Body Mount

Here's some research I did this morning to supplement our bolts and washers.

Bob here are some more data points for you regarding the 1967 hardware I have here. Sorry for the hen-scratching. I also did some AIM comparisons, 1963, 1966, and 1967 with some notes.

First, more measurements. Hope they're readable. If not I'll redo them darker.
.
1967 Washers:
Edit: 12/1 AM - Replaced photos as I goofed up on one of them it was not centered on the measurements. Also zoomed in for clarity.
20231201_075000.jpg

20231201_075048.jpg

20231201_075039.jpg



Here are the AIMS.

1963

1963_1.jpg

1963
1963_2.jpg

====
1966

1966_1.jpg

1966
1966_2.jpg

======

1967_1_Convertible.jpg

1967_1_Coupe.jpg

1967

1967_2.jpg


========

[Leif A.]

Re: Bolt Size for #4 Body Mount

Rich and Gary,
As you're both very aware, AMK products can be (sometimes) useful for specs on hardware. From their website:

The #3772263 bolt...
Hex Flange Bolts 3/8 - 1/27/16-14 X 2 5/8 GR5 FLNG BOLT "A" PHOS. Phosphate & Oil(ONF) 3902232 (sim)



And, then the #3790768 small washer...

Washers - Flat .46 to 1.0 ID.46 ID X 1.12 D X .12 TK FLAT WA PHOS. Phosphate & Oil(MWZ) 3790768

[Gary B.]

[Bob J.]

Re: Bolt Size for #4 Body Mount

Rich, thanks for the washer measurements. I had no problems reading them.Bob

[Richard M.]

Re: Bolt Size for #4 Body Mount

Rich, thanks for the washer measurements. I had no problems reading them.Bob

You're welcome Bob. BTW, I edited my earlier post with better and zoomed in images for easier future reference.

I also added some nut measurements(NO, not my hat sizes! lol).

They were all 7/16-14 threads, but some had different wrench sizes. See notes at right side of page here...
20231201_075048.jpg

Anyone else ever have different ATF nut widths? These would have been at the #1 mount at the firewall as the #4 nuts were rust welded to their bolts when I cut them off.

Rich

[Joe L.]

Re: Bolt Size for #4 Body Mount

You're welcome Bob. BTW, I edited my earlier post with better and zoomed in images for easier future reference.

I also added some nut measurements(NO, not my hat sizes! lol).

They were all 7/16-14 threads, but some had different wrench sizes. See notes at right side of page here...
[ATTACH=CONFIG]119836[/ATTACH]

Anyone else ever have different ATF nut widths? These would have been at the #1 mount at the firewall as the #4 nuts were rust welded to their bolts when I cut them off.

Rich

Rich------


If I encountered so much heavy corrosion in the fasteners, I'd be worried about the rest of the frame.

[Richard M.]

Re: Bolt Size for #4 Body Mount

Rich------


If I encountered so much heavy corrosion in the fasteners, I'd be worried about the rest of the frame.

Joe, I restored the frame ~8 years ago. A L71 convertible. Except the 2 #4 bolts that were very badly rusted, the others came out easily. The frame was good and I repaired or replaced sections that were marginal. The inside box channels had some scale and I removed it and zinc coated then blacked it out.

I replaced both rear #4 frame mounts, Differential crossmember gusset that was cracked(common on BB's), End Caps, etc. You may remember it. Here.

Now the next one I did, a '66 convertible, the frame was so bad that after I took the body off(it took a entire day to get the 8 body mount bolts out) and stripped the frame, it cracked at the kick-ups as I was hauling it out back. It all started when the owner walked out into his garage and saw gallons of fuel on the garage floor "inside" his house! The fuel line was rusted out. I got a reproduction frame for that one. This One.

Rich

[Gary B.]

Re: Bolt Size for #4 Body Mount

…They were all 7/16-14 threads, but some had different wrench sizes. See notes at right side of page here...
[ATTACH=CONFIG]119836[/ATTACH]

Anyone else ever have different ATF nut widths? These would have been at the #1 mount at the firewall as the #4 nuts were rust welded to their bolts when I cut them off.

Rich

Rich,

The #4 nuts were large square nuts captured in cages, I believe.

The #1 nuts changed from GM 124573, which were zinc, 5/8” AF, to GM 9418897, which were black phosphate, 11/16” AF, with an AIM revision date of 10-27-66. So, early MY ‘67 cars would have the 5/8” AF nuts, and later MY ‘’67 would have the 11/17”. (The exact same part number change happened with the majority of bumper nuts during the ‘67 model year.) I wouldn’t be at all surprised to find some ‘67s with a mix of these two AF nut sizes at body mount #1 around or even several months after the 10-27-66 revision date.

Ah, but I see you list the AF sizes as 9/16 and 5/8. Are you sure they aren’t 5/8 and 11/16?

Gary

[David B.]

Re: Bolt Size for #4 Body Mount

Nut 9418897 is 7/16-14 GM 4435-M code A spec. phos. coated, oil treated & 72 hr. salt spray.

[Richard M.]

Re: Bolt Size for #4 Body Mount

Rich,

The #4 nuts were large square nuts captured in cages, I believe.

The #1 nuts changed from GM 124573, which were zinc, 5/8” AF, to GM 9418897, which were black phosphate, 11/16” AF, with an AIM revision date of 10-27-66. So, early MY ‘67 cars would have the 5/8” AF nuts, and later MY ‘’67 would have the 11/17”. (The exact same part number change happened with the majority of bumper nuts during the ‘67 model year.) I wouldn’t be at all surprised to find some ‘67s with a mix of these two AF nut sizes at body mount #1 around or even several months after the 10-27-66 revision date.

Ah, but I see you list the AF sizes as 9/16 and 5/8. Are you sure they aren’t 5/8 and 11/16?

Gary

Gary, You were right. I had them wrong. So this March '67 had a mix at the #1 mount.
20231201_164631.jpg

Nut 9418897 is 7/16-14 GM 4435-M code A spec. phos. coated, oil treated & 72 hr. salt spray.

Thanks David.