427 Fan Core support/Rad washers diameter?

[Keith B.]

Just finishing my rebuild on my L-36. On my last TF judging I got dinged for improper washers on my rad core support washers thru rad to shroud.

I bought my 66 from the org owner with 39k org miles, so many items were correct. However, I have these two center THICK washers that were in the middle of the core support and they look really old. They are 1.25 inch in diameter and almost 1/4 inch thick. The other 4 washer on either side that go thru the top Rad brackets are also 1.25 inch in diameter but the standard washer thickness (thin). My AIM calls for a P washer and bolt, my Paragon and CC Central Catalogue just call them washer and bolt. My Noland Adams Tech C2 Book looks to have the large washers but it is hard to tell in the blk/white pictures.

Can someone with some authority tell me the proper items to have here, bolt washer, what thickness and what diameter washer. I believe I have the right head and length bolt. Much appreciated.......

[Richard S.]

Re: 427 Fan Core support/Rad washers diameter?

Keith,

I think you're going to find there is no actual absolute "positively correct" answer to your question. For many years now I have been carefully examining these washers on 66 and 67 big block cars....especially the non restored and survivor cars. From what I have been able to determine from these observations and discussions with many senior NCRS members, the size and actual number of washers used varies widely.
The current 66 Judging Guide is probably your best bet just now. Hopefully, someone can post pictures of these washers on known "original" cars or a "National" level judge can offer comment to help you out.

[Gene M.]

Re: 427 Fan Core support/Rad washers diameter?

I only worked on one 66 bb that I believe the radiator was original and not messed with. And it had the large diameter 1/4" thick washers as you described and all were the same. Outer bolts had sleeve spacers.

If memory is correct (no bets on it) washers were plain, little rusty steel.

[Joe L.]

Re: 427 Fan Core support/Rad washers diameter?

Just finishing my rebuild on my L-36. On my last TF judging I got dinged for improper washers on my rad core support washers thru rad to shroud.

I bought my 66 from the org owner with 39k org miles, so many items were correct. However, I have these two center THICK washers that were in the middle of the core support and they look really old. They are 1.25 inch in diameter and almost 1/4 inch thick. The other 4 washer on either side that go thru the top Rad brackets are also 1.25 inch in diameter but the standard washer thickness (thin). My AIM calls for a P washer and bolt, my Paragon and CC Central Catalogue just call them washer and bolt. My Noland Adams Tech C2 Book looks to have the large washers but it is hard to tell in the blk/white pictures.

Can someone with some authority tell me the proper items to have here, bolt washer, what thickness and what diameter washer. I believe I have the right head and length bolt. Much appreciated.......

Keith-----


From your post it's not clear to me which washers you are referring to. If you are referring to the washer identified as GM #3688003, GM says that washer was 5/16" ID, 1-1/4" OD and 3/32" thick. If you are referring to some other washer, please identify.

[John H.]

Re: 427 Fan Core support/Rad washers diameter?

We've seen both thicknesses of washers on different cars over the years, but all six locations (the two that attach the fan shroud bracket to the radiator support on all '66-'67's, and the four that attach the big-block upper radiator cushion brackets to the radiator support) specify the P/N 3688003 washer in the A.I.M.

As Joe noted above, that 1.25" diameter flat washer is "normal" 3/32" thickness, not the super-thick (3/16"-1/4") version we see occasionally.

[Keith B.]

Re: 427 Fan Core support/Rad washers diameter?

Gentlemen: Thank-you for investigating this subject.

Joe, I'm referring to the top six rad core support bolts/washers to shroud and left/right top rad brackets with rubber underneath.

Attached are two pics of my washers. The top row are the (4) 1 1/4 " OD and 5/32 Thick. The vast majoirity of my 97.7% TF car is original, especially the rad, core, shroud, etc. These washers really have that 43 yr old look to them.

The bottom (4) washers are also 1 1/4" OD, and 3/32 thick, they look newer because I just replated them. All my bolt heads are R S C with 6 / slash marks, I think they are correct.

To be honest both washers look to wide for this application but on page 355 of Noland Adams C2 Tech guide book it appears to have Thick washer against the core support the the thin washer on top of it then bolt. To look visually nice I think the washers should be 1 " or less so they don't ride over the lower lip of the rad core support but factory correct I think I might have the right bolts........Thoughts fellas upon viewing pics.....Keith.

[Joe L.]

Re: 427 Fan Core support/Rad washers diameter?

Gentlemen: Thank-you for investigating this subject.

Joe, I'm referring to the top six rad core support bolts/washers to shroud and left/right top rad brackets with rubber underneath.

Attached are two pics of my washers. The top row are the (4) 1 1/4 " OD and 5/32 Thick. The vast majoirity of my 97.7% TF car is original, especially the rad, core, shroud, etc. These washers really have that 43 yr old look to them.

The bottom (4) washers are also 1 1/4" OD, and 3/32 thick, they look newer because I just replated them. All my bolt heads are R S C with 6 / slash marks, I think they are correct.

To be honest both washers look to wide for this application but on page 355 of Noland Adams C2 Tech guide book it appears to have Thick washer against the core support the the thin washer on top of it then bolt. To look visually nice I think the washers should be 1 " or less so they don't ride over the lower lip of the rad core support but factory correct I think I might have the right bolts........Thoughts fellas upon viewing pics.....Keith.

Keith-----


I agree that the photo in Noland's book appears to show 2 stacked, large diameter flat washers. However, I have no idea why such a configuration would have been used. I've not seen such a configuration in very many applications and never in an application like this. Plus, it's not the configuration shown in the AIM. It may have been used, though, for reasons unknown.

I think the 3/32" thick washers in your photo are the 3688003. While you have had them re-plated, I assume they were originally plated zinc or cadmium which is just how the 3688003 were supposed to be.

I don't know what the thicker washers were. These appear to be un-plated, natural steel. It's very unusual for such washers to be used in such an application. However, I don't doubt that they were originally used. I would expect it was some sort of "production line mod" and for what reason I could not guess. Keep in mind that while they may be original to your car, that does not mean that they were "typical of factory production".

[Keith B.]

Re: 427 Fan Core support/Rad washers diameter?

Thanks Joe: When I re-did my rad core in 2004, the year I bought my 66 from the org owner, the washers were positioned just like Noland Adams photo page 355, thick then thin washer set-up. Personally it looks funny to me as at 1 1/4" both sit high above the slot of the Rad Core support bracket. Anyway, I think I will put them back this way and argue my case if I get deducted again in August in Leavenworth as this is how my car left the factory..........

[Joe L.]

Re: 427 Fan Core support/Rad washers diameter?

By the way, there is a currently available GM replacement for the 3688003. It's GM #14015619. However, it has a bit different specifications. It's 13/32" ID, 1-1/4" OD, 1/8" thick, and phosphate finished. You've got to really want one of these, though, since they GM list for $11.78/each.

[Michael H.]

Re: 427 Fan Core support/Rad washers diameter?

Typical 66 big block. Illogical, but correct.

[Wayne W.]

Re: 427 Fan Core support/Rad washers diameter?

Typical 66 big block. Illogical, but correct.

I have always thought the reason that the thick washer was added was to make sure the bolt didn't cut into the radiator. Notice how close the bolt would be if the washer wasn't used. My opinion is ,they had some that would hit and made the change for that reason.

I think the reason for the large diameter washer was to keep the rail from collapsing. It spreads the stress out over a larger area. There were also some spacers under there to keep that from happening.

[Keith B.]

Re: 427 Fan Core support/Rad washers diameter?

Michael: Thanks for the original BB picture of the washer set-up. This is exactly how my 66 came when I bought it in 04 from the Org owner. Like I mentioned I was deducted at my last Regional and told the thick washers were all wrong. With you pic and Noland Adams book, although they look strange I'm going to put them back together this way as mine came from the Factory. Very interesting research and topic though.....

[Richard S.]

Re: 427 Fan Core support/Rad washers diameter?

Michael's photo of a 66 configuration is representitive of what I have observed at many events over the last 15 years on many "original" and "survivor" 66's and 67's. However, I have also observed smaller, thinner and multiple washers of different sizes. I don't have the most current Judging Guides for 66 or 67....only 3 older versions of each.....what does the current JG call for?? Thanks for the opportunity to review and discuss.

Rick.

[Mike B.]

Re: 427 Fan Core support/Rad washers diameter?

Good Evening Keith,

I'd like to resurrect your very informative 2009 thread here. I was hoping that you (and others) may shed some light on a few questions that my friends and I have on this subject. I know it's been a long time but hopefully you've kept your notes.

I've been researching the thick natural steel washers present on many '66 & '67 427 radiator core supports. I've read as many threads as I could find in the archives and although they've been very informative, your thread here is the only one I could find that shows these thick washers laying flat separated from the thinner wide washers.

The main question my friends and I have is what is the inner diameter hole dimension of the thick natural steel washers? You and Joe both state that the thinner wide washer #3688003 dimensions are 5/16" ID, 1-1/4" OD and 3/32" thick. And Keith you state in this thread that your original natural steel washer dimensions are 1-1/4" OD and 5/32" thick. Do you have a dimension of the ID hole? These thick washers in the top row of your photo appear to have a larger hole than 5/16"?

If true this coincides with photos of said originals. These thicker washers are often seen slipped off center underneath of the thinner 3/32" thick 5/16" ID, 1-1/4" OD washers. And just to complicate things a bit more we've seen some '66 BB cars with the same OD thick and thin washers together while some earlier cars appear to have the thicker washers with a wider OD than 1-1/4".

We really enjoy this thread. We hope to hear more on this subject. Thanks.
Mike

Gentlemen: Thank-you for investigating this subject.

Joe, I'm referring to the top six rad core support bolts/washers to shroud and left/right top rad brackets with rubber underneath.

Attached are two pics of my washers. The top row are the (4) 1 1/4 " OD and 5/32 Thick. The vast majoirity of my 97.7% TF car is original, especially the rad, core, shroud, etc. These washers really have that 43 yr old look to them.

The bottom (4) washers are also 1 1/4" OD, and 3/32 thick, they look newer because I just replated them. All my bolt heads are R S C with 6 / slash marks, I think they are correct.

To be honest both washers look to wide for this application but on page 355 of Noland Adams C2 Tech guide book it appears to have Thick washer against the core support the the thin washer on top of it then bolt. To look visually nice I think the washers should be 1 " or less so they don't ride over the lower lip of the rad core support but factory correct I think I might have the right bolts........Thoughts fellas upon viewing pics.....Keith.