New Fel Pro Manifold Gasket... major leak!! Help..... (1 Viewer)

[Bluegrass40]

I pulled my header to weld up a hole. The old gasket was a paper type gasket. I never had any leak issues with it (other than the big hole in one of pipes).
I did some research and decided to go with a fel pro manifold gasket. I installed everything today. When I started it up, there was a very large leak on the 2nd and 3rd exhaust ports (from the front). I installed it with the exposed metal flanges toward the header/intake manifold (per instructions). It seemed like the gasket sat on the studs properly and lined up with the bolt holes. When I put the intake manifold and header on, it looked like something was wrong. Like the metal flange on the gasket was sitting too high relative to one of the ports on the header. I was not that surprise when it leaked. It was like it was not sealed at all. I loosened all of the bolts and tried to shift the gasket down and the header up, but it still looked like it was going to leak. I tightened up everything and sure enough... It leaked.

Am I missing something obvious? I'll try to snap a pic tomorrow and post it.

One other thing to note... The header and intake flanges are different thicknesses. The washers have been ground down on one side to address the flange height difference.

Thx!

 

[bgray]

Everything I've read states that you should have the surfaces and bolt flanges milled at a machine shop to the same thickness, so mating surfaces need to be the same thickness and separately the flange/ears for the bolt holes need to be the same thickness. I called a machine shop on this the other day and they quoted $90 for the complete procedure. As well, most folks state that the Remflex gasket is the best.

...again, this is based on what I've read vs. personal experience, but it makes sense.

Brian

 

[Solace in Solitude]

You can use half-washers to compensate for the different thickness of your header and intake 'ears' - I did mine that way - no leaks.

But, it's best if they are milled the same thickness - my machine shop didn't have a tool to handle milling the headers.

HTH

 

[DougAustinTx]

I try to avoid milling the mounting ears on the exhaust and intake, I don't want to weaken them. Instead I add brazing rod to the exhaust ears (on the nut side of course) and level it with a flap wheel. If the intake needs a little more thickness, it only takes a few minutes to TIG some aluminum on the ear to build it up. Same procedure with the flap wheel to level it with the exhaust. The trick to making the gasket seal is to have perfectly flat gasket faces on the intake and exhaust manifolds, then make sure the clamping forces are equal on the nut side of the manifolds. In my experience, you don't really need to preserve the washer indentations in the ears of the manifolds. They can't really move anyway when all the studs or bolts are in place. When dealing with an original intake and headers, I have found that it works best to put a piece of 3/16" inch thick steel about an inch and a half long and 3/4" wide with a hole drilled in the center for the stud or bolt, and eliminate the round washer entirely. The steel bar will usually have some tension across both the intake and the header flange to clamp them tightly. You can also put a slight bow in the steel bar to increase the clamping effect. Hopefully you can see the steel bar washers in this photo.

 

[Bluegrass40]

Thx for the replies guys. I'm planning on swapping out my header for a set of 3fe exhaust manifolds in the not too distant future soon trying to avoid any extra investment in the header (aka, don't want to spend any $ on machining). I'll take everything off and look at the impressions on the gasket for some clues. I may try to add some shim stock below the washers and see if it will seal up any better if the gasket looks to be centered over the ports.


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[Bluegrass40]

I like the idea of the 3/16 stock to help seal. May give that a go as well


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[tyama]

Hiya, I recently replaced both my gaskets. I couldn't pull the manifolds to get them milled so I used the remaflex gasket. They have seemed to hold up pretty well for the last six months. We'll see if they keep on doing good.

Good luck, ty

 

[sggoat]

I installed a Tri-Mil header on my '77. Had to grind out a bunch of weld voids first before I got the thing flattened. Amazing I had to go to 3 machine shops before I found one that actually knew what I was talking about to get the clearances flat against the head. They got it right(finally) and have had no issues with leaks since install.

 

[Howard705]

This is a header. I don't think anybody normally machines the surface on them. It sounds like it is misaligned with the hole. Flatness won't matter. How did it align with the ports in the head? Is it the correct gasket? I think hotrod guys use sealer btw. When I've done these with stock manifolds I left the bolts loose between the two manifolds so that they can "float" -snugged the head most of the way then tightened the manifolds together-then tightened at the head. Have done this on Fords in the past. .

 

[Bluegrass40]

Thx for all of the info, guys.
I think I found the likely issue. I want back to take some pictures and post and noticed that one of the washers by the port that was leaking looked odd. Took out the bolt and found that the washer was not sitting on the exhaust header flange but has slipped past it!

. I was getting virtually zero compression on that joint.
I removed the intake and shifted the exhaust header as far forward as possible then installed the bolt/ washer and scribed a line on the header to see what amount of engagement I would get.

It was very little. (you can see the scribe line if you look close)

I'm going to make a new washer to increase engagement. Will post pics when done.



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[DougAustinTx]

This is a header. I don't think anybody normally machines the surface on them. It sounds like it is misaligned with the hole. Flatness won't matter. How .

On the contrary, flatness DOES matter on the header flanges. I have two sets of Tri-Mil headers and both of them needed to be machined flat on the mating surfaces. They were off by a large amount and would not have sealed with a single gasket. The fit up of parts on gasket surfaces should always be correct before the gasket is installed. While apparently not the problem with the OP's setup, it will eventually become a problem when the exhaust leaks start popping.

 

[want2wheel]

I would weld that area up and have it machined back down so the maiting surface area on the flange is larger.

 

[Howard705]

Grind it a little smoother/flatter. Make sure the gasket doesn't shift one way. Use Large thick washers or the rectangular steel. Re tighten after running a few times.

 

[darwink1]

Having the same issues with my felpro. Im running a man a fre header and I now have an exhaust leak just under and in front of the carb.

Id like to try the bar washers, can someone post up how many bar washers are needed, some rough measurements for them including hole size and thickness of flat bar used? The torque sequence for the intake and exhaust nuts would finish the thread off nicely.

I know its obvious when looking at the motor as to how many and what size but my van is at a buddies getting electrified so I cant take a look. Id like to make them up before I head out to his place again and try em out. I have a new gasket on stand by but am curious to see if the washers will do anything with the old one in there.

Thanks in advance guys

D

 

[allan man]

Some folks use 2 gaskets and have had success.

 

[Bluegrass40]

Problem solved!
Did some more investigation today.
Found that the sealing surface of the header was totally shifted relative to the gasket metal sealing surface! I pulled the intake and header and lined them up off the head and found that the header ports were shifted relative to the pattern on the gasket. (Wish I would have snapped some pics). My old gasket was a paper type gasket which may have been less sensitive to the alignment issue. So I ended up grinding on the header flange to allow it to shift up relative to the intake/ gasket. I also slotted the mount holes In the gasket to shift it down slightly. I then put copper coat on the gasket and header and bolted it up (for literally the 8th time) making sure to shift the header up as much as possible. Problem solved!!

I def recommend people with headers and fel pro gaskets give the port alignment a check if there is a leak. I have a feeling that the paper type gasket may have not had this issue.




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[sggoat]

On the contrary, flatness DOES matter on the header flanges. I have two sets of Tri-Mil headers and both of them needed to be machined flat on the mating surfaces. They were off by a large amount and would not have sealed with a single gasket. The fit up of parts on gasket surfaces should always be correct before the gasket is installed. While apparently not the problem with the OP's setup, it will eventually become a problem when the exhaust leaks start popping.

Exactly what I found on my headers!!