Core Support Mount Differences?

[special-K]

What is the difference between 67/68 and 69/72 radiator core support mounts?I never realized they were different.But,looking through some catalogs I see them listed different.Even the bolt is listed different.I guess you go by which support you have,huh?I`m putting`67 sheetmetal on a`71 frame.

[Richard Dobson]

I'm puttting a 68 front clip on my 71 Chevy. LMC offers only one radiator support bushing set for 67 thru 72 trucks, while other vendors like Brothers offer different sets for 67 thru 68 and another set for 69 thru 72. The 67-68 frames have small holes in the frame while 69-72 have larger holes. Unless you weld in some spacers the make smaller holes so that the 67-68 bushings can be used in the 69-72 I think we have no choice. Could this cause problems as far a front fender alignment to the cab I don't know. Maybe some of the other board members who have done this same 67-68 front fenders on a 71 truck will give some input.

[chevychase]

I didn't think there was much of a difference either but from the pics below obviously there is.

1960-68



1969-72

[sameyrasmea72]

This is a 69 frame. On a 67-68 the mounting hole is about the size of a silver $ i think.

[sameyrasmea72]

Thats not a verry good pic. It makes the hole look smaller than it really is. This onr is a little better.

[Richard Dobson]

I just measured my 71 frame holes, 1.70 diameter. I don't know the 67-68 hole diameters but I know they are smaller. Hence the bushing difference. I appreciate the board member giving so much detail like pictures etc. Can we have some more input because this would be handy before I get to the reassembly process and have fit-up problems. Thanks everyone.

[Green Machine]

The core supports are really the same dimension wise, it the head light bucket thing that is different. The key here is to use radiator mount bushings that match the FRAME, not the SUPPORT. 67-68 used the thinner washer type setup with a small hole in the frame, AND the metal supports on the frame are mounted higher. 69-72 went with a larger hole and taller bushing type mount and the frame mounts are located lower on the frame to make up for the taller rubber bushings. Hope that helps.

[special-K]

Thanks for clearing this up,guys.I never ran into this before and the books just list them as different with no explanation.I`m sure Green Machine is right,go by the frame.There really are no other differences other than hole diameter and cushion design.The body parts are all compatible dimensions between 67 thru 72s.It all makes sense now.

[Green Machine]

Yep, learned this the hard way, tried to fit some 69-72 bushings on the 68 once - no go - sat so high the bumper would not fit, and had terrible fender gaps at the door, fenders were way to high in front.

[special-K]

That would be a bad day,alright.It never hit me until now,but all the trucks Ive done have been`69 or newer.I`ve had some 67s & 68s but never tore one down that far.

[Green Machine]

Don't want to get this completly of topic, but a similar situation happens on the frames of any 4wd and the 2wd C20. The rear cab mount rubber bushings there are longer than the C10 2wd trucks. The cabs are the exact same, but the steel mounts on the frame sit lower, thus requiring a longer rubber mount. I'll quit for now.

[special-K]

I just looked at my LMC "bible".Maybe it isn`t such a great reference book.Yet another incorrect listing that would not only through the unimformed off,but sure would "P" a guy off trying to use parts he ordered that won`t work w/o modification.It`s more like,"This is the right part because it`s the only one we sell".

[msgross]

Here's a 68... only 1 1/8" hole for the support

[special-K]

So,while you`re measuring...what does your front track measure from outside to outside?

[msgross]

about 6' 8" or so... to big for that trailer

[special-K]

It prolly wasn`t heavy enough anyway.Most likely 6,000# and I`d want an 8,000#er.

[Hart_Rod]

Bringing up an old thread....I must have missed it, but I'll ask anyway, is there a height difference in the bushings? If so, what is it? Thanks,

R/

[Tim Christian]

You must use 67-68 rad support bushings for a 67-68 sheet metal and 69-72 rad support bushings for 69-72 sheet metal. It does not matter what year frame 67-72 has nothing to do with it.

[jaros44sr]

You guys are the best for info...wondering why my fenders were not lining up on the bottom rear mounting hole...

Is there a height differance on the rubber blocks and how much? Maybe cut the rubber blocks down

[K15]

Originally Posted by Tim Christian

You must use 67-68 rad support bushings for a 67-68 sheet metal and 69-72 rad support bushings for 69-72 sheet metal. It does not matter what year frame 67-72 has nothing to do with it.

Just trying to wrap my head around this. I have a 72 K15. Dynacorn is out of stock on the 69-72 core support (p/n 1099za) but have a 67-68 (p/n 1099ya) in stock. All my sheet metal and frame is original 1972. From what I understand I can use the 67-68 core support but there may be differences in the mounting bushings (diameter/height). Thanks.

[71meangreenc10]

The thickness of the bushing kits are different. The 67/68 have thin bushings and the 69/72 are thicker. I put a 69/72 core on a 68 and used the 68 bushings. All went well so far. What I saw in the differences in the years was the early core supports have tapped holes in the bottom for the cover that goes across and the 69 and up does not. The dimple is there, just not threaded. The buckets in the 67/68's are different, those "should" be able to be changed out to newer ones. Everything else in the casting of the core support looked to the eye to be the same.

Some one else can chime in. But I measured a lot on two different core supports and they came out the same.

Just to be clear, my core support went on a 68 GMC. We laid these supports side by side for comparison.

Smitty

[K15]

Thanks, I didn't think the GMC headlight buckets would be different across the years but I have the old ones already stripped off the original support if I need to modify the new one.

[71meangreenc10]

Originally Posted by K15

Thanks, I didn't think the GMC headlight buckets would be different across the years but I have the old ones already stripped off the original support if I need to modify the new one.

The differences are in the Chevy ones for sure. Look up a GMC bucket just to make sure.

Smitty

[LockDoc]

-

Originally Posted by Tim Christian

You must use 67-68 rad support bushings for a 67-68 sheet metal and 69-72 rad support bushings for 69-72 sheet metal. It does not matter what year frame 67-72 has nothing to do with it.

This is not true. The frame does have something to do with it. The brackets riveted to the frame are different.....

Here is a picture of the '67 - '68 core support bushing parts (top picture) And a '69-'72 parts (bottom picture). posted by member "Mt Man Chad". What he has labeled as a "square nut" is not a square nut, it is a square washer with a square hole in it.

LockDoc

[K15]

Just to confirm, if I'm installing a 67-68 GMC core support In a 72 GMC frame I use the 72 bushings. I suppose I'll find out eventually when I put the fenders on. Won't be for a while but I'll post results when it's done.