My 460 has always leaked exhaust from somewhere. It is quite frusterating. I have made attempts to repair it at least a dozen times. I have had the heads milled flat, the manifolds ground flat, I have tried percy high performance gaskets, no gaskets, fel pro gaskets, double fel pro gaskets, and RTV. At one point I nearly had the truck exhaust leak free, however, when I took the manifolds loose this last time to rebuild the motor, I have yet to have them seal properly again.

I need someone to share their secret. I know I must be missing something.
I have taken manifolds off of other vehicles and reused the old gasket with no problems. But this particular 460 is really driving me batty!

 

I just use red rtv. works fine.
Install header with the rtv (making sure the ports line up right). Run the engine around the block and retighten all bolts. Check them after 500miles and you are good to go.

 

Thanks for the quick reply. I too usually use rtv, but I have not been having luck with it the last 4 or 5 times I have tried... How thick of a bead do you usually run?

 

Maybe the leak you hear isn't coming from the exhaust manifold. Try taking a length of small diameter hose, like fuel hose, putting one end up tight to your ear and use the other end to find the leak. Move it around each port and the coupling with the exhaust pipe. Also around the hot air choke tube plate and the egr plate. Hope you find it!
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I just had a customer's truck do the same thing. He had a big repair made just below the flange and the last guy left a BB sized hole in the pipe. I fixed that but it still leaked. I resealed the manifold, it still leaked. I double gasketed it, it still leaked. I finally gave up and put a new manifold on it. Then it was silent until you torqued the engine under load. Then it would tick just a little bit.

If you find the answer, please let us know, because I'm dying to know what the heck was leaking on his. (it was the passenger side manifold.)

 

I had an engine,460 i think, not sure it's been a few years and i'v had about all of the ford engines. But it had a leak,i found on the back side of the heads next to the fire wall there were some ports that had some tubes sticking out that had been cut off and closed up. I believe they had something to do with the air pump emissions system that had been removed. There were leaks there that sounded just like an exhaust leak. I removed them and capped them off the correct way and no more leaks. Attach a small hose to a small funnel ,funnel to your ear and end of hose to the back side of the heads should locate any leaks. Good luck.--

 

I use those caulk gun sized RTV tubes from o'reilly's. I dunno, probably a 1/4inch bead. I hand tighten everything so the two surfaces are against one another. I then sit on a bucket, drink a cup of coffee and roll a few cigs. Burn them, and go back to retighten everything once the RTV is hardish.

Never had a leak.
Finding the leak is easy enough, find the soot. If not, baby powder makes a good leak checker

 

Kinda off topic, but not really.

Would this work for sealing my collectors? I had the paper gaskets and they leaked so I bought some the percy's dead soft aluminum gaskets and they still leak between the bolts (I have the three bolt flanges). Do ya'll think it would seal up if I ran a 1/4" bead of read RTV around each side of the percy gasket, bolted it back up and let it sit for a while (a day) to get "hard" before cranking the truck up again.

Thanks,

 

Like someone said..common spots are the emmission lines.

Ive also seen a few 460 that the heads crack at the exhaust port.Its more common with the EFI motors.

 

The yellow truck had what sounded like an exhaust leak at number four. I tried gaskets and bolts, but never actually found proof of the cause. It did have the "head-to-head" pipe that had been capped off - that could have been leaking. It also had broken and missing intake manifold bolts, seemingly causing an internal cooling leak. But that is all behind us now...