I have a question about 5.8 heads and the differences in the exhaust port locations. New exhaust manifold gaskets do not fit and I'm having a hard time figuring this out.

Here's what has brought me to ask. I have a 92 f150 with a 5.8 that recently began to leak exhaust out of the right bank. Before getting started I went to my local parts store to pick up a set of exhaust gaskets and a couple of cans of spray penetrating fluid. Long story short, the new flepro ms90000 gaskets do not fit. They are a about a half inch too long length wise -- height seems ok. Seems to me that the exhaust ports on the set of heads I have are just a bit closer together.

Any ideas? I've been to two parts stores and since this motor didn't have exhaust manifold gaskets from the factory, my Ford dealer is not much help.

Thanks for reading and look forward to hearing some feedback.

 

All late model windsor heads are the same but unfortunately gaskets are another story. When you say they are too long do all the bolt holes line up?

 

I don't use exhaust gaskets. clean both surfaces real well, then spread a thin coating of graphite on. torque the manifolds to spec. I always instal new studs in the manifolds while they are off, saves a headache later

 

Thanks for the responses!

As for the bolt holes in the exhaust gasket lining up question: no not all of them do. I'm working on the right bank; cyls 1-4. It appears that cyl 1 and 2 are close but not quite right on. Cyl 1 has a bit of an over hang while 2 seems to be spot on. For cyl 1 the bolt holes line up but the the gasket is too small for cyl 1's port -- cyl 2 is spot on for both the bolts and the exhaust port. Cyls 3 and 4 are about 1/4 inch off to the right. Kind of like if you were reading from right to left -- they end up being offset by about a 1/4 inch.

My best guess now is to cut the gasket in half and get 1 and 2 to align as best as possible and then trim a bit on cyl 1's ex port and then do the same for cyl 3 and 4 to get them to align where needed.

As for just cleaning up the manifold? It seems like the 17 or so years has left it a bit pitted and perhaps somewhat warped - although I haven't straight edged it yet. The pitting leaves me thinking that a gasket will take up at least most of the small imperfections which is what I'm hoping for.

How does the graphite apply here? Does it just smooth out the torque process when installing? Is there something that might fill in the pitting in the exhaust manifold like a gasket might?

I'm okay with doing a bit of trimming on the gasket if that what it's going to take, but that still leaves me wondering why a standard off the shelf gasket for a 5.8 (351) just doesn't fit. I'm under the impression that these heads have, for the most part, been reasonably the same for the 35 years (give or take) years they have been in production.

Still willing to learn more about this whole thing, so feel free to chime in.

Thanks again for your input.

Mark

 

If your manifold is warped you'll never get it to seal properly, you're better off having it machined flat and just bolting it back on or use some grahpite sealant on it. Sounds like the gasket you have is a particularly bad I have never had that much trouble with one.

 

Yeah, it's a curious problem. For what's it's worth, I went to 2 parts stores out here and both of the gaskets are off in the same way. Since 2 gaskets sets from different shops didn't fit, I figured that it was the head / manifold that was different. Very strange.

I'm not familiar with graphite sealants, so I'm need to read up on that.

Thanks again for all the help!

Mark

 

I also meant to ask if you notice the alignment problem with the gasket against the heads or the manifold itself.. or both?

 

someone stuck the wrong gasket in the right box. 5.0, and 5.8 both heads are the same, and the gaskets should match. I agree with seeing if they match up to the manifold too. trimming it will not work, the surfaces need to line ip, and if the gasket covers the port in any way, it will burn out before the engine even warms up. the graphite is the same product you would use to lube door hinges. I spray the manifold with wd40, and shake it on with a salt shaker. bolt it up and torque it, if any leaks, the graphite moves into that spot. this is a tsb from ford, that's how the dealerships repaired them under warrenty back then. manifold has to be true, and not warped though, which is what probably blew out your gasket to begin with