Exhaust Bolt question

[Joe L.]

Re: Addendum

Brandon-----

I'm pretty sure that the one you took off is the correct one. However, I'd greatly appreciate it if you would perform the little procedure I described previously. It would help me confirm if it's original and also provide other information that would be useful. It will just take a few minutes to wire brush the stud threads and check it with the 3/8-16 nut.

Also, the stud does go on the forwardmost, left (driver) side, exhaust manifold bolt position, but only if the car also has power steering.

No french locks were used for your application. Also, no washers, lock or otherwise, were used on LS-5 exhaust manifold bolts.

[Brandon Thompson]

Re: Addendum

Thanks Joe!

Ok so just for the record I can go ahead and slap my manifolds on without using any sort of locks, washer or anything! I woulda never guessed that they just bolted the exhaust manifolds on like that without any washers or locks but I take your word thats the route I'll go. So I assume these are those locking bolts you mentioned before?

btw my car is a PS car.

I attached a pic of the kit I ordered I'll be using those - the stud one I will re-use my old one. I bought um from paragon it's the PR #: 1725K
Exhaust manifold bolt and stud kit. All B.B. w/P/S, no A/C. Includes 15 bolts and 1 stud.
For Years:1965 to 1974
Type: Stock
Packaging: Kit
Condition: New

they seem to be double circle and match what I took off besides the flange stud ofcourse so I guess these are ok to mount without any lock washers.

[Joe L.]

Re: Addendum

Brandon-----

This kit appears to be an absolutely correct kit for a 1965 or 1966 and some or all 1967 Corvette big blocks (with power steering). However, it's not correct for a 1968-74.

Have you been able to check that stud yet?

[Brandon Thompson]

Re: Addendum

Joe,

Yes the nut thats on the stud in the pic runs down the threads perfectly. Wow so the kit I ordered isn't right for a 68?

paragon is a rip off then bc it says the kit I ordered is for amd I quote "Exhaust manifold bolt and stud kit. All B.B. w/P/S, no A/C. Includes 15 bolts and 1 stud.
For Years:1965 to 1974 "

that matches my car since mine is a 68 big block/b.b. with PS and NO ac.
the bolts even matched what I took off my car.

[Joe L.]

Re: Addendum

Brandon-----

That surprises me. If the used stud is the stud that was supposed to be originally installed, you shouldn't be able to run the nut down by hand. That's because the original stud, GM #3928905, used special, deformed threads as a locking feature. Otherwise, the stud appears EXACTLY AS IT SHOULD IN ALL RESPECTS. It is possible that some previous person that worked on the car used a die nut on the threads in an attempt to "straighten them". That converts the threads to the normal configuration in which the stud will turn down easily (but, of course, no longer locks.

1968-74 Corvettes did not use french locks as did earlier big blocks. The reason that they did not was because the locking feature provided by the french locks was replaced by locking bolts (and studs for any positions requiring studs). These eliminated the need for french locks and that's why 1968-74 were built without them. These bolts, GM #3909821, were used on the end runner positions, both sides (except when a stud was used as is the case for the p/s application). They were a FLANGED HEAD bolt, just as you note the flanged head configuration of the stud. The remaining bolts were the same as 65-67---standard hex head bolts with no washers nor any sort of locking feature.

1965-67 big blocks used the the same standard hex head bolts, GM #3736035, at all 16 positions (except when a stud was used as in the case of p/s-equipped cars). For power steering, the stud was GM #3778103 (PRODUCTION; never available in SERVICE) and GM #3774029 (SERVICE; virtually identical to 3778103). This stud is configured EXACTLY like the NEW stud in the picture that Kurt posted for you and the one in your photo of the Paragon kit.

You know that what is, apparently, your original stud is not configured like the Paragon stud. I can tell you that the configuration of the your apparently original stud is exactly as it should be (except for the threads). The bolts at the end runner positions should look just like this stud WITHOUT THE 5/16-18" EXTENSION.

So, why doesn't your car have the correct bolts at the end runner positions? I don't know. Perhaps, someone earlier removed them and, since they turned out with such difficulty, figured the threads were "buggered up" and replaced them. Not easily finding a new stud, they may have run a die on the threads to "straighten them up". Or, it may be that since 1968 was a "transition" year, strange things were done and the bolts that are one there now are the originals. Such things have been noted before on 1968's. However, my feeling is that late 1967's may have used the 68+ bolt configuration rather than any 1968's using the earlier configuration. But, who knows?

[Joe L.]

Photo Addendum

Attached is a photo of an NOS GM #3928905 stud that was supposed to be used for the forward, left side manifold bolt position for 1968-74 big blocks with p/s. Look familiar?

As I mentioned, this stud has locking threads.

[Joe L.]

Another Photo Addendum

So, what did the special GM #3909821 bolts look like? Save for headmarking, they looked like this:

[Brandon Thompson]

Re: Another Photo Addendum

Joe, I misunderstood I tried it on the new bolt, the old one yes is hard to screw the nut down on.

so if I re-use that old stud, and use my kit bolts for the 4 center bolts on each side that will be correct except for have the other 7 locking bolts on the end runners correct?

so question now is where do I get those 7 locking end bolts? if I do that and re-use the stud and use the reg. hex ones in the middle and all without washers or locks I should be correct

so the 7 I need should match the "SPECIAL" bolt you have pictured correct?

[Joe L.]

Re: Another Photo Addendum

Brandon-----

Yes, you can get them from GM under the part number I provided.

[Brandon Thompson]

Re: Another Photo Addendum

Joe, one last thing. I am going to order the 7 locking bolt I need to make the setup correct.

however I wanted you to look at the remaining bolts I will be using to see if they're correct they came in the kit from paragon...I will be using these bolts (8 of them) in the middle 2 runners on each side of the manifolds..I including a head mark picture on this post I just wanted to see if they would be correct.

and ofcourse on the other 8 the end ones I'll use the locking ones that you gave me the part # to.

thanks joe!

[Joe L.]

Re: Another Photo Addendum

Brandon-----

The overall configuration is generally correct. However, the center symbol (manufacturer's ID) may not be correct. I don't think that the manufacturer represented by this headmark was actually making these bolts in 1968. I don't think you'll get anything closer in a NEW bolt, though.

What did the bolts you took off the engine look like? You may be able to reuse 8 of these if they are in good shape and otherwise correct.

[Brandon Thompson]

Re: Another Photo Addendum

Joe, like 4 out of the 16 matched the center 8 that I will need. They are pretty worn looking but to my eye they match the new one I posted a picture of with the double circle and all.

guess I will just go ahead and use the new ones in the centers.