Dreaded 460 Exhaust Manifold Leak

I had the same problem on my 1989 E350 Econolpne with a 460 engine. My problem was that one of the heads on the manifold bolts was sheared off and there was nothing but the stud left. I tried gripping the stud with a vise grip and, when I turned it, the stud broke again till it was just about even with the head. I then tried to drill the broken stud out but the clearance was way too tight. Soo, after spending about $1900 at the Ford stealership to have the intake manifold and head removed to drill out the stud I got my rv back with a big dent on the rear of the vehicle. Apparently the tech that was working on it backed into a lift and hoped I wouldn't notice it. I went back and complained to the Service manager who said they would repair the damage. When I went to pick up my vehicle, I noticed while traveling on the freeway that there was a lot of wind noise coming from the driver's door and it seemed loose. When I got home, I found out that someone loosened the striker pin thing on the door so that it would not close tightly. CAN'T IMAGINE HOW THAT COULD HAVE HAPPENED! Anyhow, good luck on repairing the manifold.

I did this job on an older E350 with a 460 in it, specifically 1983. On the Driver Side, I sprayed the fasteners with penetrant daily for over a week. Then I found I could loosen all the fasteners with a 3/8" breaker bar. All eight came out.

I had my manifold re-surfaced at an automotive machine shop that had a "belt sander." This sander is a machinist's tool, and it dresses to a tolerance close that of a cylinder head re-surfacing machine. A head machine can't do an exhaust manifold because the pipe connector part interferes with getting the manifold flat on the surfacing "surface" of the machine.

An old mechanic suggested this: Use stamped steel gaskets, NOT the fiber ones. The gaskets you linked look better to me than the steel Fel-Pro's that I used. Then Kent's advice continued: Apply NeverSeez to the head, manifold, and gasket surfaces. Then, torque NEW bolts till the stampings are crushed and STOP. The lubricant, and the lower-than-spec torque, allow the manifold to expand and contract differently from the head, without shearing the gasket.

A couple years later, it needed the passenger side done, and what I found was the bolt heads were wasted away, to less than their original 9/16" size. On the older chassis, I found I could force a long extension bar between Frame and Fender Liner, then put a 13mm six-point on the extension and pound it onto the bolt heads with a hammer from the fender well. Then Voila! Epiphany! They were all nearly Loose! From there, I did the same process as driver side.

It was clear to me that the beating I gave the passenger side was far more effective than my patient spraying the driver side.

I also replaced the OEM exhaust with a Flowmaster Cat-Back exhaust kit. We had a forum member awhile ago who did a Flowmaster kit AND an aftermarket high-flow cat converter. The 1983 wasn't built with a cat, so all I needed was a piece of pipe. Flowmaster kit was 3" diameter with very smooth mandrel bends and an enormous "big block" muffler.

I've added the Flowmaster part of the story because I believe part of keeping the manifolds from warping is getting rid of as much exhaust heat as possible and that high flowing exhaust system just had to help.

I also believe we can "abuse" our manifolds by coming down off the interstate, ducking into the first gas station, and shutting down right away. Slowing down, and idling a couple minutes, helps things to cool down gradually, and hopefully, together.