In two years I've blown out two exhaust manifold gaskets on my 54 F100, the one that goes between the right exhaust manifold and the exhaust pipe. Last summer I put some Permatex Muffler and Tailpipe Sealer on both sides to help seal any leaks from uneven surfaces. Late September I drove my 54 to a family reunion at my sister's house in Lancaster County to show it to my cousins and siblings. It is about a 160 mile drive. I drove up to 65 mph at some points. On the way home I heard the truck backfiring on deceleration. On the way to get our Christmas tree in December my wife complained about exhaust fumes in the truck.... So I better get it fixed!!!

I picked two gaskets at the auto parts store. Will putting two gaskets and the Permatex on keep me from blowing out the gaskets again? I know there must be an uneven surface, probably on the manifold side. So will two gaskets clamped down tight do the job?

 

I have same issue on my 6 cyl. blown manifold to exh pipe gasket. Last time I installed 2...and it never really sealed completely. still had some sooting. This time I installed 3 and really tightened them down. So far it is doing the job. time will tell if it is going to hold up.

 

Sanderson headers do not use flange gaskets at all, instead they recommend high temp RTV. You place a bead of RTV on the mating surface and then install the header and finger tighten the bolts...this keeps the RTV from fully compressing. After the RTV sets (not sure about the time) you tighten the bolts to torque. I realize that your issue is at the pipe and not the head but if there is an issue with a gap in the mating surfaces I would think that this RTV technique may work better than stacking gaskets.

 

I'm not clear on what type of connection you are having trouble with but I know on my turbocharged snowmobile where there is a common problem they use a multi layer very soft compound gasket from factory and some with more problems have gone to a copper gasket .

 

Are these two, flat mating flanges? Are they pitted or warped? Is it something you can have milled flat, or maybe weld a bead around to create an even pressure area around the hole?

 

Some thoughts..........If you want to fix it correctly remove the manifold and lay a straight edge across the mating surface, it needs to be flat. 223 inline six can sometimes found out of wack if the intake and exhaust 3 bolts are tightened prior to starting to snug the exhaust to cylinder head. There is a bit of movement with those exhaust to intake 3 bolts. Tightening them last may give enough movement to arrive at having a flat mating surface.

I would dis-assemble intake - exhaust replace the three hole gasket* and leaving those 3 bolts a bit loose, put the intake exhaust assembly back on the head and working from the center out snug the assembly to the cyl head bringing it tight against the head without the gasket, do this in increments always working out from center. Then tighten the 3 bolts that mate intake to exhaust. Remove assembly and put a straight edge across the long mating surface. If there any gaps I would suggest machining that long mating surface flat. Don't forget the metal rings that go into the intake, imo they are necessary.

*The mating surface between the intake - exhaust can be also rough and hard to seal. I have made copper gaskets out of about 28 ga copper sheet ( about .014") by chiseling them out and then annealing the copper gasket by heating it till you turn the copper black and then let air cool, The annealed copper will crush and help fill voids in the mating surface. Even if there is a slight leak the copper gasket will not burn out like the metal-ized fiber gasket.

Double gaskets, RTV etc I see as stop gap and likely temporary. Anywhere the gaskets don't crush flat the exhaust gases will work on and eventually burn out the gasket.. The up side to taking all the pains is longevity and also no stress on the exhaust from forcing the intake-exhaust flat. Manifolds getting harder to find and they seem to command a premium $ anymore.

V-8's .......if the sealing surface is not flat ( straight edge) re-surface the mating surface., My 2 cents.

 

X2 on what Charlie is saying. I don't have a 223. But a 302, and the driver side exhaust flange uses one of those sintered donut style gaskets. Its also at a 45 degree angle. It is hard to get the connection straight and sealed correctly. So whenever I have had it apart I use a new gasket and a nice bead of Hi Temp RTV. Like Charlie says you leave it loose for a little while, then torque the flange bolts down. I let mine sit for the rest of the day so it cures. It seems to have solved the leaks at that connection. Also I use it on my exhaust manifolds instead of a gasket with good success. The stuff I use is the Permatex Ultra Copper.

 

I believe he is talking about the manifold exit connection not the manifold to block .

 

There seems to be some confusion here. My truck is a 239 Yblock V-8 with the crossover pipe. The blown gasket is where the right side exhaust manifold dumps into the exhaust pipe.

Charlie Leds suggestion of high temp RTV sounds like a good one. Here is what I used last time.


Here's the gaskets:


So, two gaskets and RTV or one gasket and RTV?

 

I wouldn't think that two would be of any advantage as those are not a multi layer squashable gasket . I do think the not fully tightening until it has set would have some merit although I have not tried it .

 

I get where you're at, the manifold to the head pipe connection. But is that connection two flat flanges butting together with the gasket in the middle? Are the flanges clean, flat and true, or are they warped and/or pitted? Is there some reason you can't achieve a good seal? I looked in my parts catalog and they don't show a picture of your exact application, but in all the other pictures, they show the head pipe with a short piece sticking out that fits into the hole in the manifold, as well as the gasket and flange. This would direct the exhaust gasses through the pipe before reaching the gasket. Assuming you've had the exhaust system replaced, is it possible the head pipe was made incorrectly and doesn't have the part going into the manifold correctly?

 

Pretty sure what abe is talking about is the right manifold to the cross over pipe on his Y -block

 

Abe's first sentence was

so that leads me to believe it's the pipe going down to the muffler, not the crossover that's the problem, but if it is, that's all the more reason to be rid of that goofy thing and go with ram's horns.

 

Yes, it is the rear of the right exhaust manifold where it dumps into the exhaust pipe. The one that is hard to get to.

 

Maybe try a copper gasket...?