'72 F600 330 CID repair rusted exhaust manifolds
 

My '72 F600 with 330 CID has badly rusted exhaust manifolds which leak a lot. I am told that the studs are easily broken and installing new ones is the usual problem. Engine removal is recommended.
If I can coax the old nuts off the studs, can I get by without replacements? I have coated the nuts and studs with penetrating oil many times, hot & cold.
Anyone have advice on this problem?
I am going deaf driving my trustworthy '72.

VIN: F60CCP10399

Please clarify.....Replacement what? Replacement nuts, studs, or manifolds??

Replacing studs. I plan to grind the manifolds.

Thanks..

If you can remove the nuts, I recommend buying new nuts and washers. Take a wire wheel to the studs and get'em as rust-free as you can. Maybe treat them with naval jelly (or similar) and then apply anti-seize.

Before grinding on the manifolds, take 'em to a machine shop and have them run on a mill to get them dead flat... sometimes a run on a large-face belt sander works good too...

And for the rusty manifolds or studs that came out with the nuts (as so often happens)....Try this low-buck solution: Electrolysis - Rust Removal. Paint them with high-heat paint afterwards.

I set up a vat on my patio for only $30 and it works really, really, well. It'll also unfreeze and de-rust parts that have corroded together. Do it.

One thing to be aware of...sometimes it's not so much the manifolds but the heads that are warped. The top ears on the manifold mounting flange can be pulled out a bit causing the flange to warp, which of course makes it very hard for the manifolds to seal. You could very well wind up having to pull the heads to have the manifold flanges surfaced. Hope not, but it's a possibility and something to check when you get it apart.

According to the 4th digit of the VIN (C), your truck has a 330 2V M/D FT engine.

1970/72 330 2V M/D; 330 2V H/D; 361 & 391 FT engines:

4) 379521-S7-8 .. Stud-Exhaust Manifold to Cylinder Head ~ 3/8" -16 -16 x 3 21/64" long.

Two studs for the right manifold, two studs for the left manifold.

All the rest are: 20522-S8 .. 3/8" -16 x 2" Hex Head Bolts ~ Exhaust Manifold to Cylinder Head.

FoMoCo did not install exhaust manifold gasket-to-cylinder-head on these engines, just metal heat shields. Sooner or later, the manifolds begin to warp, start ticking.

Whiz down to the autoparts store, buy FT exhaust manifold gaskets and have the manifolds resurfaced.

Invaluable, guys. You all just saved me pulling the engine. Now, I can pull the heads and manifolds together, though not looking forward to the back strain of working so low in the compartment.

I hate to see you pull the heads if you don't actually need to. On the other hand, I was working on a 360 a couple years ago that had a horrible exhaust leak, and in the process of getting manifolds off I managed to break three of the bolts off in the head on one side. Since it was the manifold flanges on the head that were badly warped (worst I've ever seen) there was no way to make it seal without getting those surfaces flat so I had to take the heads off. That made it much easier to get the broken bolts and get them out, and I discovered when I got the heads off that the head gaskets were rusted almost all the way through and one of them had less than 1/8" of material left between the cylinder and a water jacket, so those gaskets didn't have much life left in them anyway.

My point exactly. Tigerdan. When the motor was completely rebuilt 1990, the head work required two attempts before it acted correctly. I am told that this engine has had problems with manifold bolts, so I am expecting the worst.
I am relieved to pull the heads, rather than the whole engine.
The engine runs fine, performs well, except for the exhaust leaks.
Thanks.

HIO, the vat that you described is interesting.
Can you describe it? What vessel? What solvent and what strength? How long do you soak?