Exhaust Manifold Studs

[Lee S.]

In a previous post, I requested assistance and guidance to replace the positive battery cable in my 1974 Coupe (454/THM400). I'll update that posting soon.

Now, I've run into stripped/rusted LS exhaust manifold studs. I have had a small exhaust leak here for some time. Now I know why. I put penetrating oil on them daily for 4 - 5 days. Using vise grips, I grabbed one stud close to the top to avoid further damage to the threads on the lower portion. Without excessive force, this stud was not going to break loose. I decided to leave well enough alone and attempted reassembly with a new donut. Only one stud has sufficient/quality thread exposed to hold the nut. My next course of action is:
1) Buy a new thread chaser (lost this size) and clean up the threads
2) Buy new stainless nuts (I know... not correct) for the studs on both sides. Are washers used? The right side is OK but I may as well replace the nuts there. I always use Anti-Sieze in these applications.
3) Pray this works

What is my course of action if I still can't get the nuts tightened down? I have been reluctant to force the studs hard enough to break them off. Can and how are they drilled out?

[Mike G.]

Re: Exhaust Manifold Studs

Lee: There is really only one choice, in most cases. Remove the manifold. Heat the flange around the stud to cherry red. Unscrew the stud & install a new one. Sounds like a lot of work?? Try drilling out a broken stud without trashing the threads in the manifold!

[Wayne K.]

Re: Exhaust Manifold Studs

Lee,

Have you tried heating the manifold or hitting the stud using a punch ? Some people have had good results with heating the area and letting wax melt into the frozen stud. After it cools they say the stud will come right out. I've never tried that one so good luck.

Wayne

[Lee S.]

Re: Exhaust Manifold Studs

Thanks... I'm going to try and clean-up the threads and use new bolts. There is nothing to lose. I was afraid the alternative would be remove the manifold, heat, etc. The wax process is new to me.

Fortunately, the LS manifold is a bit easier to get at. My car has AC. You can imagine what the RS looks like. Thanks again.

[Christopher R.]

Re: Exhaust Manifold Studs

I don't know that a thread chaser is going to help. A thread chaser will cut material. Sounds like you don't have enough material to begin with.

If you have enough stud showing, try double nutting it.

You can replace the studs. If you do, buy the brass nuts that are sold for this application.

Don't "cob job" this. You won't be happy. A spitting exhaust drives me nuts. The old studs can be drilled out. If you don't feel you can do it, bring it to a machine shop.

[William V.]

Re: Exhaust Manifold Studs

Lee

The manifold stud size is 3/8-16. If you have to drill and tap use a heat riser as a guide to help keep the drilling straight.

Bill

[Chas Henderson #28127]

Re: Exhaust Manifold Studs

Take the manifold off and take it to a muffler shop and for about twenty dollars they will heat them up and remove them. Then you can clean them up and install new studs and hopefully, never have to screw with them again. I did this with my 71, cleaned them up , coated them, and used never-sieze and I check on them every other year. They look great and I put over 4k miles ayear on the car.

Chasman

[Lee S.]

Re: Exhaust Manifold Studs

Great ideas... thanks

[Kurt B.]

Re: Exhaust Manifold Studs

I had this same problem and I removed the manifold from the vehicle and used Mapp gas (like a propane torch, buy it in any hardware store for under $10) heated it up real good, applied some penetrating oil and let it cool and then backed them out with vise grips. This method works for me on anything I cannot remove and was taught to me by a very old but very wise mechanic. Since then I stopped breaking things and stripping threads. The heat does all the work.

[mike cobine]

DO NOT drill out Exhaust Manifold Studs

especially on the car. You will never get them straight and you will probably end up with steel in the eyes.

The cost of going into the eye doctor or emergency room far outweighes the hassle of taking the manifolds off to have them done.

If it runs, take it to a muffler shop or a friend who has a torch set. If you have a trailer, do the same. You can be done in 15 minutes with a torch, compared to all messed up with a drill.

And heaven help you if you break a bit off in there.

[Mike McKown]

Re: Exhaust Manifold Studs

What is my course of action if I still can't get the nuts tightened down?

I think you're wasting your time. Best course of action is to pull the manifold and heat it up. They'll usually come right out with no problem.

[Lee S.]

Re: Exhaust Manifold Studs

I have, and use Mapp Gas... hot stuff (pun intended). Hit it with the penetrating oil hot? That will make for some excitment. I have good access to the studs. I wonder if I should attempt this with the manifold on the car? I fear my attempts to remove the manifold will lead to stripped bolts retaining the manifold to the cylinder head. I'll be removing the cylinder head next. I'm stuck in the restoration vortex!

Kurt - I'll let you know of the outcome on the starting issue. I have some digital photos of the cable which clearly shows corrision several inches from the solenoid towards the battery.

[mike cobine]

Save yourself a lot of trouble

Pull the engine.

It seems extreme, but the number of cut and busted knuckles, broken bolts, and so on that you avoid having the engine on a stand to to all this is well worth it.

Especially since you said you have AC in the car.

[Lee S.]

Re: Save yourself a lot of trouble

Wow, that's extreme! I just replaced the positive battery cable and the transmission tunnel insulation WITHOUT pulling the engine or transmission. I have cut and busted knuckles on top of cut and busted knuckles.

You are kidding, I hope.

[Lee S.]

Re: DO NOT drill out Exhaust Manifold Studs

Agreed... never, ever have I been successful or seen success drilling out something like this.

If I can't clean-up the threads, it's time for the torch. Maybe mine, maybe Mr. Muffler.