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My Galaxie has a 390 in it and it makes noises like a valve chatter when under a load going up hill. It goes away if you push the gas petal down or let off.

But I know for a fact that I have a bad exhaust leak at the gasket on the driver's side exhaust manifold. Could this be causing it?
 

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But I know for a fact that I have a bad exhaust leak at the gasket on the driver's side exhaust manifold. Could this be causing it?
Sure can.

Is the leak at the head mating surface or where the down pipe attaches to the manifold?

While I never had trouble with any of my FE engines leaking at the head mating surface, I did have the same problems with Lincoln 430/462 MEL engines leaking at the mating surface.

If this is your problem, pull the manifold off & take it to a machine shop & have the surface machined true. Then put it back on with no gasket, just metal on metal. Your car may have a stamped metal heat shield sandwiched between the head & manifold, you can keep that if it's in good shape.

If it's leaking where the pipe connects to the manifold it might just need to be tightened or it could need a new donut gasket.
 

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or a cracked manifold..
 

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Discussion Starter #4 (Edited)
Sure can.

Is the leak at the head mating surface or where the down pipe attaches to the manifold?

While I never had trouble with any of my FE engines leaking at the head mating surface, I did have the same problems with Lincoln 430/462 MEL engines leaking at the mating surface.

If this is your problem, pull the manifold off & take it to a machine shop & have the surface machined true. Then put it back on with no gasket, just metal on metal. Your car may have a stamped metal heat shield sandwiched between the head & manifold, you can keep that if it's in good shape.

If it's leaking where the pipe connects to the manifold it might just need to be tightened or it could need a new donut gasket.
It's at the mating surface where it mates to the heads. I was hoping that was what was causing it, it's a great motor, doesn't smoke, and still has plenty of power to it.
 

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or a cracked manifold..
That's also a possibility. Or even a broken flange in the bolt hole area. When I used to tinker on 430/462 MEL engines it wasn't uncommon for them to develop little cracks in the ports that would leak. I'd pull the manifold, have the cracks welded and mating surface trued & it'd be good to go.


jeremyl

Just curious, why eliminate the gasket after the machine shop work?
There shouldn't be a gasket there in the first place, from the factory they just have stamped metal heat shield thing. If the surfaces are true it'll seal better metal on metal than with a gasket there. If you insist on putting something there just do what I do on the manifold to turbo flanges on my Dodges, smear a little grease on there & it'll burn & turn to carbon in a matter of seconds.
 

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If it is not even and you don't want to machine it, then a gasket will have to do.
 

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On my 360 truck engine I must have changed the gaskets 4 or 5 times and it would be OK for a month or two and then start leaking again. I finally pulled the manifolds and took to a machine shop to have the surface redone. Used gaskets and red permatex when I put them back on and it hasn't leaked in over 8 years.

One good thing about changing the gaskets so ofter is that the manifold bolts were never a problem to get out, after the first time. First time I had to use a torch to get some of them out.
 

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Which bolts are harder to get out? The ones along the top, where you can see the shank of the bolt, or the ones along the bottom?
 

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Which bolts are harder to get out? The ones along the top, where you can see the shank of the bolt, or the ones along the bottom?
Seems like the top ones break more often. That's what I've seen in a few pics and I had one of my own like that.

Also if you machine the exhaust manifold flat but leave the head alone you're only fixing half the problem. Out of the two sets of FE heads I've had both needed to be milled flat, although neither looked as bad as the one in Putt's pic.

If you're going with headers you're probably going to need some gaskets but it wouldn't hurt to hook it up and try it without first. If it won't seal up, installing gaskets later is pretty quick and easy. Be sure to use some anti-seize on the bolts when you put it together.
 
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