The New Life of the 3800 "Formula"

[TopNotch]

On this manifold, the three tubes that go to the exhaust ports are all tied together by a metal bar, and the bar is attached to the head. Studs are used in most places, but there are also two bolts used. You can see one of the bolts in this picture. I have no idea why it's that way.
Because of the bar, I don't think the manifold would have to be mounted to be welded. And I don't think brazing with it on the car is a good idea. The work actually gets hotter with brazing than with welding, because the work must be heated enough to melt the brazing rod. With welding, just the immediate area of the weld is heated by the electric arc.
Edit: The blackened spark plug boot is right above where the crack was. It's just surface blackening.

[TopNotch]

Good luck with the fix. Please let us know. I tried something similar - a JB Weld product, I think. It lasted for about an hour. But that was a long time ago. I hope the technology/chemistry has progressed some, in 15 years.

I went to the store in the car, and the fix held that long at least.
The VersaChem stuff is a water-based paste I think. It has no smell. I think it is some kind of ceramic, and the heat of the exhaust works like a kiln to harden the ceramic. The problem with that is that if there is vibration of the crack, that could work a ridged ceramic loose. I'll keep test driving it and see what happens.

[TopNotch]

Now that I've had a good look at the rear exhaust manifold on my car, it looks at least partly home-made. It looks too crude to be a factory job. And I looked at 95, 96, and 97 manifolds sold on Rock Auto, and it doesn't look like any of those. So one way or another, I will have to fix it myself.
Here's one I found on Rock Auto. Mine definitely doesn't have the big opening in the middle, but just the cross-over pipe connector. Otherwise, it looks the same, including the EGR tap-off on the left port connection.

[TopNotch]

Well, the muffler sealer didn't work, and fell out of the crack. So I decided to try welding it on the car.
It just so happened that a while back, I bought a new solid state "stick welder" (one that uses welding rods, not wire). I hadn't tried it yet, because it runs on 240V, so first I had to add a 240V outlet in my garage.

Because the welder is solid state, it is very small and light weight, compared to my old Harbor Freight wire welder. In this picture, it is tuned on with the current set to 41 amps.

I first did a little test weld on a piece of angle iron, and that worked pretty good

So now it was time to try it on the manifold. Unfortunately, I had the current set too high, and burned a couple of little holes in the manifold. So I turned it down (70 to 41), and was able to fill the holes and the main crack. It's awfully ugly, but a lot better than that VersaChem stuff.

[TopNotch]

I put another VersaChem product, called "Muffler Weld" over the welded area and any crack outside the welded area. This product is dark gray, not white, so it looks better, and it seems to stick to the metal better.
I let it harden overnight, and drove to the store today. The exhaust noise was quieter than it's ever been, indicating a good seal. While I was welding, the heat seemed to make the crack outside the welding area close, and the weld has held it closed. The engine is quiet enough now that I can hear things I hadn't noticed before, such as a slight valve train noise. So far, I'm happy with the result.

[TopNotch]

I made a stethoscope out of a piece of plastic tubing and listened around the weld for exhaust leaks. I found some, wire-brushed off the VersaChem stiff, and did more welding, and it looks like this:

Now the only leak I can hear is around on the engine side of the manifold, where I can't reach with a welding rod. I may yet have to take the thing off. But for now, I packed in some of that VersaChem stuff with my finger on that side. After it dries, I'll check for leaks again.

[TopNotch]

I guess that because there's a shortage of cars to buy these days, more people are fixing up their existing cars. The Maaco where I had my white car painted is booked solid until October 25, until I can take my car in to have the RFTH boo-boo fixed.

[TopNotch]

Today I removed the exhaust manifold with the cracks in it to fix them correctly. I as too cold after I got it out to finish the job, so I'll do that tomorrow.

[TopNotch]

It seem like that every time i take something apart on this car to work on it, I discover another "short cut" the original builder of the engine swap did. The exhaust manifold I took off was mounted with no gasket -- just metal to metal against the head. Now I'll have to check the other side to see if it was put on that way, too.

[Raydar]

It seem like that every time i take something apart on this car to work on it, I discover another "short cut" the original builder of the engine swap did. The exhaust manifold I took off was mounted with no gasket -- just metal to metal against the head. Now I'll have to check the other side to see if it was put on that way, too.

Are you certain that the manifolds have ever even been off the engine?
I've taken stock (cast iron) manifolds off of several engines over the years. They were always "metal to metal". Not even a steel shim gasket.
Of course, the reason they were coming off was so that I could install headers, so I always went back with gaskets. 

[TopNotch]

I'm pretty sure the manifold had been off the car. It appears to have been modified (somewhat crudely, which may be why it cracked). The entire exhaust takes the same path as a stock V6, and I don't think it was that way in the donor car. And carbon traces on the manifold indicated that it leaked slightly where it was attached to the head.
Edit: In any case, it has a gasket on it now.

[Raydar]

Ah. Okay.
Didn't realize that it followed the stock path.

[Fierofool]

I thought stock 3800 exhausts crossed over to what is our trunk side.  Their firewall side.

[TopNotch]

I thought stock 3800 exhausts crossed over to what is our trunk side.  Their firewall side.

My trunk side manifold looks like this, except that it doesn't have the big pipe outlet on it.