Cracked 454 exhaust manifolds

Where is it cracked, vertical crack in between the exhaust ports? If so don't worry about it. The replacement manifolds now have gap or cut in between the exhaust ports to allow for expansion. I have a 94 and mine cracked there, I had to replace it because the rear stud was already busted and the studs for exhaust pipe flange wouldn't come out. For $50 I wasn't going to try and remove those 3 studs. Anyway the replacement had a gap right where mine was cracked.

A no cost solution. The manifolds will have to be removed. Use a drill to elongate each bolt hole approx. 1/8th inch on each side of bolt hole. This will allow the exhaust manifold to expand and contract as it heats and cools. Torque bolts to spec.

Where is it cracked, vertical crack in between the exhaust ports? If so don't worry about it.

X2

If it is not leaking leave it alone. IMO the risk of a broken hard to remove bolt is too high.

If you 'Someday' determine that U should have replaced the manifold, make sure you get the BEST metal, Aftermarket manifold gaskets you can find! This is the only thing that will protect manifolds. Many 454s came from factory with no gaskets! If U don't live in a state with Exhaust Inspections, Remove the Air pump that blows air into the exhaust manifolds & get shorter belt. Use Vice-Gripe pliers to pinch off each(8)cylinder air tubes.

My 89 454 manifold cracked at 4,000 miles. Very common.

Mine were cracked in a few places and leaking. I sprayed them two or three tones a day for about a week with PB Blaster while I waited for my Doug Thourley ceramic coated headers to show up at my house. Every stud came right out with no problem.

1998 pass the bad cracking years. Studs on a GM big block often can be screwed out but not so much the case with a Ford Big Block. I have one of each.
They all screwed out of the 1992 454. He had to weld a nut on the one broken off to screw it out.

If they ever go to leaking then replace them.

Hank MI wrote:
The replacement manifolds now have gap or cut in between the exhaust ports to allow for expansion.

X2. Hank is right on.

jolooote wrote:
If you 'Someday' determine that U should have replaced the manifold, make sure you get the BEST metal, Aftermarket manifold gaskets you can find! This is the only thing that will protect manifolds. Many 454s came from factory with no gaskets! If U don't live in a state with Exhaust Inspections, Remove the Air pump that blows air into the exhaust manifolds & get shorter belt. Use Vice-Gripe pliers to pinch off each(8)cylinder air tubes.

Actually no gasket and a liberal amount of anti-seize grease is recommended. They're going to expand and contract, you can't stop it. The anti-seize grease will allow them to slip against the head when they do. The grease may burn off but the aluminum, copper and graphite in the grease will remain.

Thorley used to sell a rubberised gasket that is very good. Might be able to find them at Doug's headers. As far as getting the bolts out, you can spray with Kroil, which is a hair better than PB Blaster. Or mix Acetone and ATF. I found when removing the bolts, I set my impact on the lowest setting, and just let it bang away lightly till the bolts came out. I had only sprayed them the day before, and was just messing around with the impact. I figured on the lowest setting, I wasn't going to break anything, so I just figured I would see what would happen. Much to my amazement, every single bolt came out. I had not planned on really getting into that project yet, but when the bolts started coming out with out much trouble, I kept going. I think there is something to be said for low impact persistent banging on the bolt till it comes out.