To make a short story long, I have noticed my 460 in my RV getting louder and louder over the last 12 months, mainly when the engine is not warmed up, and just after starting it. It's very obviously coming from the right side. When I hit a certain speed it quiets down a lot and stays that way once the engine is hot. Because of this I suspected that it was an exhaust manifold gasket leak. I also notice some exhaust noise above 65 mph, especially under load, which at that speed and 5.5 tons, it usually is under a pretty good load. Also the sound pretty much seems to match the RPM of the engine and only from one cylinder.

Anyway, I've heard that the 460 is notorious for studs breaking off. So today, I was working on my van's and my RV's dash air systems looking for leaks, and I decided to pull the engine cover on the RV to check this out. I started it and by running my hands near the manifold at the head I found right away a gush of air coming from the farthest back cylinder. (4 or 8, whichever that side is)

Anyway, 1 stud is either gone or almost gone, while another is broke off and sticking out just slightly from the manifold. Both are the backmost studs on the exhaust manifold. I do most of my own easier engine work unless it gets to where I have to tear the engine apart and then I don't care to do it, but I don't have the $$$ to pay for it either. I figure I have to drill each of them out and use an easy-out to get them out and then replace them.

But, does the gasket now need replaced too?

And then the most important question, is there some temporary fix to seal off the leak rather than fix it like I should? I figure that RTV probably won't handle the heat. I don't care if I have to redo it after several months as I think it would be easier than replacing the studs, plus I only use this for longer trips maybe twice a year. Maybe JBWeld?

 

Well are you siting down?

These can be a real bear to fix!

More than likely you will break more bolts trying to get the exh.manifolds offf.(a trick is to get the engine hot and attempt to loosen bolts)
there is a metal gasket between the manifold and the head it needs to be replaced .
the problem you have is there is no room to drill out these bolts.

We ended up pulling the motor to get to some of the bolts.

The common cause of the bolts breaking in the first place is .
When manifolds heat up and expand the holes in the manifold were to small so the expansion and contraction of the manifold would break the bolts off
When getting the manifolds off make sure you chk them for flatness at the flange ,take a metal ruler or square lay it along the flange .

I hope your luckier than me.
Rich

 

Ford has a TSB about this problem. They also have revised exhaust manifold bolts.

When I got my 88 F250, it had three broken off bolts: both #1's, and the leading #5. When it warms up, it mostly stops leaking.

Some previous owner put JBWeld on the leak(s). I did the same so as to smog the truck. The JBWeld doesn't last long - say 100 miles.

(I'm hoping that I can get at the broken bolts with a right angle drill...)

 

Well so much for JB weld then as my trips are usually 3000 miles at a time. I can get to the rear bolts as they clear the floor of the RV but, to get to the rest to replace the gasket, that's another story. I've wanted to put headers on it so I guess that will be my next step instead of fixing this.

Thanks for the repsonses!