C2 Manifold to Exhaust Pipe Nuts

[Gary B.]

Buying nice used originals

John,

Any suggestions as to who would have nice, used originals?

Gary

[Joe L.]

Re: Marsden nut

Need a few myself for 64FI with N11, but here's what is confusing -

63-65 FI calls for 3814568 an integral hex nut 3/8 in G3.275

53-72 the 3829086 which is the subject item appears in my 64AIM for the reg exhaust and N14 (use "prod nut") however the N11 is not shown! Said nut, 53-72, is also listed in G3.613 as a zinc finish with anti-seize coating.

The nut for N14, 65-67, is listed in G8.916 and another possible nut for 70-72 is in G8.917 So some differences appear to exist for the non standard exhaust systems. The 3829086 just may be the general service replacement!

Interesting how these questions expand!

Alan------


First of all, GM #3814568 is a STUD and not a nut. It is, however, a stud with an integral hex nut. A photo is shown below. It was discontinued by GM in July, 1983 but it's available in reproduction. I don't think it was used for an exhaust pipe-to-manifold stud for any application, though.

I have no information that any nut used for the exhaust stud application for N-11, N-14, or L-84 was any different than the nut used for any other application. I'm not saying it was not, but I have no information to that effect. Plus, I can see no reason why it would have needed to be any different for cars equipped with any of those options.

The GM #3829086 nut is the nut that GM says was used in PRODUCTION for the exhaust stud nut for all 1963-82 Corvettes. Also, every AIM from 1963 to 1982 shows this nut as the one used.

John Daly provided some excellent information that the 3829086 nut was originally spec'd out in April, 1962 (which, incidentally, is just about the time I would expect given the part number) and revised in 1973. The 1973 revised spec description sounds like a Stover-style lock-nut which is exactly what GM had available in SERVICE for, at least, the last 20 years under GM #3829086. Presumably, this style was also used in PRODUCTION after about 1973. Also, it might very well be that the pre-73 style was the style shown in the various photos that contributors to this thread have posted.

As far as the "Flex Lock" style nuts which were originally used for some early C3's, I don't know what to think. However, as Mike Garver points out from his experience, different style lock-nuts may have been alternately used if they otherwise met the GM performance specifications for the part. As I theorized, the use of these nuts may have been an "experiment" or "trial run". One possible reason I could see is that I believe the "Flex Lock" nuts would require less installation torque than either the original or Stover style 3829086. That may have been seen as an assembly aid. In any event, after what's been revealed in this thread, I don't think that any C2 guys need to be concerned about the "Flex Lock" style nuts inasmuch as they were, apparently, not used during the C2 period.

[Alan D.]

Re: Marsden nut

Great summation of the 3829086 nut question!!!

I got the pn from a GM P&A Cat (71) see picture which is pooooor however it gives a ref for the nuts as Group 3.275. I looked at the pn for the 63-64 w/FI and 65 w/FI (exc. Air Cond.) which was the 3814568 and noted as (integral hex. nut 3/8" front end)
The fact that it only calls for 1 and not "AR" -- and the "front end" should have lead me to look at the reference in Gr3.275 to B3.613 manifold to exh. pipe that calls out the now famous 3829086 nut.
(That section also lists a washer, 3754153, which I assume has something to do with the crossover pipes)

So these studs go where??? Often wondered about them.

[Michael H.]

Re: Marsden nut

So these studs go where??? Often wondered about them.

I think the stud on the left is a 3814568. It would be used to attach the exhaust manifold to cyl head in only one location for 63-65. The outer threaded portion is used to mount the choke air intake pipe.

One or two of the others look like later C2 or C3 big block????

[John D.]

Re: Buying nice used originals

John,

Any suggestions as to who would have nice, used originals?

Gary

Gary. johndegreg@aol.com

[John D.]

Re: Marsden nut

Great summation of the 3829086 nut question!!!

I got the pn from a GM P&A Cat (71) see picture which is pooooor however it gives a ref for the nuts as Group 3.275. I looked at the pn for the 63-64 w/FI and 65 w/FI (exc. Air Cond.) which was the 3814568 and noted as (integral hex. nut 3/8" front end)
The fact that it only calls for 1 and not "AR" -- and the "front end" should have lead me to look at the reference in Gr3.275 to B3.613 manifold to exh. pipe that calls out the now famous 3829086 nut.
(That section also lists a washer, 3754153, which I assume has something to do with the crossover pipes)

So these studs go where??? Often wondered about them.

Alan, On your 64 FI car you have a clean air tube on the drivers side exhaust man. area. As Hanson said the one stud looks likt it. But it definitely didn't use that nut. Remember all the posts about the flat washer under the AC GF-90 fuel filter bracket??? Well that stud and clean air tube are held on with an SAE flat washer (same as filter) and a readily available nut. JD

[Rich P.]

Re: Marsden nut

Great summation of the 3829086 nut question!!!

I got the pn from a GM P&A Cat (71) see picture which is pooooor however it gives a ref for the nuts as Group 3.275. I looked at the pn for the 63-64 w/FI and 65 w/FI (exc. Air Cond.) which was the 3814568 and noted as (integral hex. nut 3/8" front end)
The fact that it only calls for 1 and not "AR" -- and the "front end" should have lead me to look at the reference in Gr3.275 to B3.613 manifold to exh. pipe that calls out the now famous 3829086 nut.
(That section also lists a washer, 3754153, which I assume has something to do with the crossover pipes)

So these studs go where??? Often wondered about them.

Alan,

The studs on the right are small block water pump studs. The shorter stud is pre AIR with just the alt bracket attached to it and the longer stud is post AIR (smog) as the AIR pump bracket as well as the alt bracket attach to it.

Mike, you are correct the one on the left is the long small block exaust manifold stud that attaches the choke tube.

Also ALL the unrestored mid years I worked on had the nuts pictured in post # 18
I regularly come across these and list them.

Rich

[Alan D.]

Re: C2 Manifold to Exhaust Pipe Nuts

The LI nuts were not correct - judges spotted them at 09 Regional. Now these are 3 years old so LI may have changed them, but check first.

[Rich P.]

Re: C2 Manifold to Exhaust Pipe Nuts

Like I had said if you hunt you can come across them. here's the last set I had a few weeks ago.

Rich

[James W.]

Re: C2 Manifold to Exhaust Pipe Nuts

The picture that Rich posted are the same ones I have on my cars and in my spare parts stash. My family owned a couple of auto exhaust shops back in the late 70's through the mid 90's. We instructed all of out mechanic/technicians when replacing head pipes to keep all of the acorn type nuts that came off of the any 60's vintage Chevrolets.


James West

[Michael H.]

Re: C2 Manifold to Exhaust Pipe Nuts

Like I had said if you hunt you can come across them. here's the last set I had a few weeks ago.

Rich

Yup, that's a correct style for 60's cars. Kinda what I said here, too, about 99 posts ago. I've never seen any other type nut for this application and I've sure seen a LOT of them in that time period.

[Michael G.]

Re: C2 Manifold to Exhaust Pipe Nuts

I had to wait until I returned from Kissimmee to take this picture of the latest exhaust nut supplied by Paragon last week. This is not the same as the nut John Hinckley posted a few days ago, so its obviously different from the ones found on most mid-years. Paragon must have changed to this design. This part is more typical of GM lock nuts and is probably a lot easier to find today than the earlier shape.

Mike

[Joe L.]

Re: C2 Manifold to Exhaust Pipe Nuts

I had to wait until I returned from Kissimmee to take this picture of the latest exhaust nut supplied by Paragon last week. This is not the same as the nut John Hinckley posted a few days ago, so its obviously different from the ones found on most mid-years. Paragon must have changed to this design. This part is more typical of GM lock nuts and is probably a lot easier to find today than the earlier shape.

Mike

Mike-----


This is exactly the same Stover-type nut as GM sold under the original GM #3829086 part number for at least the last 20 years. Based upon the information that John Daly provided, it looks like the 3829086 specs were revised in 1973 to this configuration. Presumably, 1973+ Corvettes used this nut in PRODUCTION.

[John D.]

Re: C2 Manifold to Exhaust Pipe Nuts

Like I had said if you hunt you can come across them. here's the last set I had a few weeks ago.

Rich

Rich, Nice pic of the real deal nuts. Sorry I am late on the post as I didn't know it was still going on.
Like I said none of the tool catalogs have it.
Would be a nice nut for someone to reproduce. JD

[Ken A.]

Re: C2 Manifold to Exhaust Pipe Nuts

You guys should try your local FORD dealer. They had ones that were exactly like the picture a few years ago. Your engine won't care where they came from...............