I put the EFI exhaust manifolds on my 86 300. I have an exhaust leak but it's small. I only hear it under load. I think it's here where it connects to the pipe.
See the black spot on the side of the engine?
I was wondering if I need the donut gaskets? Do these manifolds even use the donuts?

Thanks

 

Wait till the engine is cold, start it up and run out really quick and run your hand around the manifolds and feel for the leak. You will have a little bit of time before it gets to hot to touch.

From the picture, those manifolds do not use donut gaskets. If it's leaking on the pipe to exhaust manifold connection, all you can do is tighten it up some more, or take it off and re-position it to see if that helps.

 

It's quite been a while since I've messed with those 300 EFI manifolds, but I don't remember all those extra nuts in between the flange and the manifold. It looks like that low hanging nut on the right side of that flange could be affecting your ability to tighten that side. I know that parts stores sell replacement stud kits. I'd consider investing in one of those.

 

Are you a cop?



Same thing on my 5 liter, I got some exhaust sealant from NAPA,

dropped the system in the front, applied sealant and reinstalled

after cleanin' up the threads on the studs. Used anti-seize on the

studs.

 

Thanks guys, I'll try all these. I do have to stick my hand in there quick. I gets hot quick. I'll see if I can get the studs out without breaking them. I've never seen exhaust sealant before but I'll certainly look for it.

Thanks!!!

 

Don't take the studs out, take the nuts off and clean up the threads.

I think you'll find the nuts that hold the flanged cup are brass, I swapped

mine out for steel I believe they're 7/16-20. I had to ask about the sealant,

they kept it behind the counter.

...Rusty

 

No, there are no donuts in there.
Those nuts we see on the studs should get taken off, they are probably preventing you from tightening your exhaust up fully.
If you want, I know you can buy new studs from oreillys. If you can Id pull them old ones out and replace them w/ new ones. Heat the **** outta the manifold around the stud holes, they will turn out easier that way.

 

Those nuts we see on the studs are most likely part of the stud itself. Ford manifold studs have a hex in the middle between the 2 different threads. Odds are that side had backed out a bit at some point in time and hasn't threaded back in.
Personally I prefer to replace the studs with Ford parts, as the manifold side is actually a tapered thread.

 

82 is right. A couple of the manifold studs have backed off. The nut is part of the stud and should be against the manifold.

 

Yes the nut is part of the studs. I got replacements from RockAuto.
No they aren't backed out. They are screwed in as far as I could get them. I was afraid of breaking them off if I put anymore torque on them.

Dave's idea worked, Thanks. Cranked it cold and stuck my hand in there quick. I can feel it. I'm goin to take some air tools to it this Saturday. I appreciate it gemtlemen.

 

Be careful with the air tools, you don't want to break a stud off in the manifold.

 

Spraying with PB Blaster and letting it soak over nite might make things come apart a little easier. You might have to shorten the studs od the manifold side so you will have more room to draw the flange tighter. Have you tried tightening them while they are hot? Be careful not to break the studs when you do this and not to get burned, but it might be all you need to do.

 

I agree, i thought they came with nuts, but its been a few years since ive owned an I6, and i was unsure. But they are also correct in that those nuts should be up against the manifold. Those holes thread all the way through, w/o the nut there you should be able to keep screwing them in until they fall out the other side. Time/heat/corrosion may have gummed up the threads, tap out the holes before you put an impact on them, or pieces will come apart from togetherness.

 

My exhaust leak is now fixed. Thank you one and all!

I was very surprised that the manifold studs were much easier to screw in than when I first installed them. I did hit them with some Tri-Flow a couple of hours before. Anyway, I laid off the air tools and just put a 2 foot rachet on them. I got them screwed in all the way. I used a little high temp sealer for good measure and it's nice and quiet now. Well, quiet in the Cab. The Summit Racinf turbo muffler has a nice sound outside.