I was installing a new fuel pump on my '67 GS 400 today and decided to fix an exhaust leak while I was at it. There was a chunk of exhaust manifold gasket missing from the number one cylinder and it was making a racket. The exhaust manifold bolts are stainless and I had a new set of gaskets in the shop so I figured it would be snap to fix. The car has stock cast iron manifolds. I backed out all the bolts, removed the old gaskets and slipped in the new gaskets with the metallic/shiny side towards the exhaust manifold. I tightened everything up and now it leaks in multiple locations, worse than before. I have read that some people don't use gaskets. Should I give that a try or is there some other secret to getting the exhaust manifold to seal properly?
Stacey, the secret is to have the manifolds trued up either with a belt sander or if you are real ambitious a flat file. Then a small amount of permatex ultra and torque them up evenly and viola, no leaks. There may be some other thoughts, but this usually works, the manifolds unwind when they are removed from the heads, hence the warping and leakage.
There were no factory installed exhaust manifold gaskets. Try running w/o gaskets and see if you still have leaks. If you do, Roberta has the right advice for you.
Went through this a few times with my 69 400. Gasket,no gasket(thin skim of ultra) then belt sanded the manifold to true it up and it leaked again after about a month... Closer inspection(mirror) revealed corrosion/erosion on the cylinder head exhaust flange. Went back to the gaskets with a thin coat of Ultra BUT let the Ultra set up for 20 minutes or so before I installed them and I've been good ever since. I really hate an exhaust leak as much as I do having to redo the same repair again... Good luck to yah!
depending on how long it's been leaking the manifold or head may be burned away some. did you pull the manifold completely or remove the bolts and slide in new gaskets?
I solved that problem by using two gaskets....it held up for 3 months and then I sold the car..... so...??
I was trying to avoid removing the manifold completely so I just removed the bolts and slipped in the new gaskets. It looks like I will be taking the manifold all the way off to make sure both surfaces are clean and flat. I will try the cured bead of Permatex Ultra on the gasket and see what happens. Since I will have the manifold off I will probably blast and paint the it with POR-15 Manifold Gray paint. Funny how a simple fuel pump replacement leads to me restoring my exhaust manifold. Thanks for all the help!
16 years ago, I had to have the manifolds resurfaced on my '72 GS. I added fel-pro gaskets & no leaks.
Stacey, Flatten the manifolds via a big belt sander or have them milled.. and then use a very light coat of high temp form a gasket on the heads. This is only needed if there is corrosion on the head exhaust port surface. If they scrape up nice and shiny, they will seal typically. I suspect that you may have had pieces of old gasket left behind on your first attempt. I prefer to use no sealer at all if possible. Exhaust manifolds need to "move" in relation to the heads.. this is why the bolt torque is so light (18 ft-lbs) and ramp-loc bolts are used. Over time as the manifold moves in relation to the head, it will erode a gasket, and that is why, sooner or later, they always leak.
I went to town on the manifolds and sand blasted them then painted them with POR-15 manifold paint. I then made sure there were no gasket remnants on the engine and went after the manifold gasket surfaces with a hand file. They were not flat and were pretty uneven. One of the photos below shows one of the surfaces after a couple of passes with a file. Its a little bit tricky to get the gaskets lined up and the bolts in place with the RTV is still uncured but I managed. NO LEAKS of either the fuel or exhaust type after I started up. the car sounds great and no exhaust smell when driving. Thanks everyone for the help!
I use Remflex Gaskets on my 70 GSX Stage 1. They are thicker and softer than standard gaskets and I think they are made from graphite. I have had them on the car for 4 years and so far 0 leaks.
