I need to replace exhaust manifold- UPDATE
 

My 54 F100 truck has been backfiring on deceleration. There was a thread about this a while back. My mechanic at the local garage says the timing can cause backfiring. It was timed perfectly. I have an exhaust leak at where the left manifold connects to the crossover pipe. My mechanic friend I should double up the gaskets at that point. I tried that but it didn't help. The surface of the crossover pipe is flat. I didn't put a straight edge against the surface of the manifold but it looks concave.

I put this manifold on when I replaced the heads a year and a half ago because it looked better. The old manifold was very pitted. So I got it from my stash upstairs in my garage today, painted it with black high temp heat, and will put it on.

Any advice or tips? Shall I clean the surface of the manifold that goes to the heads before I install it? Or should I try three gaskets to seal up the connection between the manifold and crossover?
Pictures:
The old gasket, is burned out. You can't really see it but there are perferations in it.
https://cimg9.ibsrv.net/gimg/www.for...2e86c95e2e.jpg

I would cross file the surface of that crossover flange, and maybe hit the manifold gasket surfaces as well.

This may be a stupid question, but would high temp JB weld withstand manifold temperatures ? If so could you hit the pits on the old manifold with it ?

The heat from the exhaust will burn up the JB weld in a few seconds. You should try to find a Remflex exhaust gasket. Summit has all of the usual applications. This site lists a lot of classics, so maybe something for your 292. The gaskets are a little spendy, but worth it. Remflex Products - FCRC Machine


Dan

What did you do to your thumb Abe? That looks like a painful one..

Ben in Austin
1950 F1

I seem to recall saying exhaust leak causes backfire in your backfire thread

What needs to be done is pull the manifold, remove the studs, then with a flat belt sander true up the manifold surface. Many engine rebuild shops can do this. I always true the manifold surface that goes to the block whenever installing a manifold. My buddy has a 30" belt sander and all I do is lay it on the sander with it on and it makes it nice and flat

Have you got a decent automotive machine shop in your area? If so, run your existing manifold in to them and explain the problem. They will be able to mill that back to perfectly flat and it shouldn't cost much.

I don't remember doing it. I banged the thumb below the nail, I'm not really sure how and a few days later I saw the blood under the nail. It will grow out eventually. Not painful at all.

Good idea guys. I'd rather use the good looking manifold than the pitted one. The pitted one has at least one bolt hole broken and I am not talking about the end slot. There is a guy that planed my head for me about 30 miles away. I'll give him a call.

Thanks!

Here is an update on my backfiring problem. I know many times guys, myself included, don't report back after we've solved a problem with FTE help.

I took the left exhaust manifold off and took it and the crossover pipe to a machine shop. That day he put the crossover pipe on a big belt sander and made sure both ends of it were flat and level. He said he would have the manifold done the next week. He called me on Monday and said it was done. He had to take out the old studs before he planed it. He put new studs in. He charged me $50. He recommended that I use high temp RTV on both sides of all the gaskets. The guy at Advance Auto recommended Muffler and tailpipe sealer by Permatex. He has used it on his vehicles. Its good for up to 2000 degrees.

I painted the manifold with grille paint good for 1400 degrees. I put it back on last evening. I put the permatex sealer on the joints at the other end of the crossover and heat riser. I let it cure for about 24 hours and so I took the truck out for a drive late this afternoon.... And no backfiring, not even when decelerating going down a hill.

So thanks guys for the help. And Kevin BigWin, you were correct on that earlier thread, started by that chap in England, that backfiring can be caused by exhaust leaks.

That's a great update Abe. Glad it solved your problem.

Yes, it's great that you got it fixed, but.... where are the pictures? Pics or it didn't happen. :)

How do you take a picture of a backfire that isn't there anymore!

All right then. Here is a picture of the left manifold that does not have a leak and no backfire. Now I have to paint to paint t the passenger side manifold to match. And I will do it while installed. Lots of paper and tape.
https://cimg4.ibsrv.net/gimg/www.for...713e4e19bd.jpg
https://cimg9.ibsrv.net/gimg/www.for...43d6538e6f.jpg

And I'll have to repaint the valve cover since it for blackened and blistered from the hot exhaust.

Edit: I don't know why the picture is on here twice. I went to edit but then it appears only once!