The Stovebolt Site Forums The Shop Area The HiPo Shop Fenton headers and blown gaskets

With just a couple hundred miles on my Fentons and new exhaust system, the gaskets have blown. I'm trying to figure what went wrong. This is on a 248.

I first thought that the installer must have warped the flanges when he welded them. Then I thought maybe it takes a special gasket. Then I thought about how solid the pipes are attached to the frame. Maybe the pipes need more flex when the engine twists.

What have you guys running these done to keep gaskets in them? What are your thoughts about my thoughts?

All tips appreciated.

Cletis, i'm not sure just how solid your pipes are mounted to the frame,but that might be the possible suspect.

Like Joe says, it's got to flex/expand.

My friend had a 52 with a rolled rear pan,after a blast down the freeway,the tailpipes stuck out about an inch and a half, they were flush when cold!

Try using 2 gaskets, it worked on my 350. Those special small head bolts help, they give more clearance with the headers. O'Rielly (Checker ) has them.

Cletis, I have probably 1,000 miles on mine and no leaks, I got the gaskets from napa and have the rubber strap type hangers so the pipes can move.

I used donut gaskets at the exhaust pipe flange.
The pipes are flared at the ends to contain the gaskets.

regards,
Leon

Cletis, I have the same problem with my 248 with Fenton headers. I thing there is a little alignment problem that is holding the headers up too high and there is not enough contact between the head and headers to keep the gasket from blowing. I will try adjusting mine and let you know if it works.
Don

Just to clarify, the manifold to pipe gasket is my problem, not manifold to head.

I always attach the headpipes to the manifold first, and tighten them up, before I attach anything aft, like hangers, mufflers, etc. I've had mine apart and back together several times trying different mufflers, still the original gaskets with no leaks.

Good luck.

Back when I was a kid, you ALWAYS mounted the head exhaust pipes to the Fentons with doughnut gaskets. ALWAYS. They even make two types of doughnuts, the kind for the flat flanged front header used with a flared pipe and the beveled doughnut for use with the beveled rear header which also uses a flared pipe. Most muffler shops have the doughnuts - I think it's a Fel-Pro gasket. Unless a muffler shop has never put dual exhausts on an inline Chevy or GMC six, they might not know that.

That is what I have. There is no donut groove cut into the headers. The guy put the flat flanges on it. And the pipes are welded together and to each other. There's no bolting them up separately.

The gasket they used look like the top set in the picture. The bottom set with the crush ring looks like they would hold better. Both together might be what I need.

Charlie - Every set of Fentons I have ever seen are as I described in my earlier post. I have about seven sets in my possession and they all are flat on the front header and a beveled gasket surface on the rear, but that is really not the point here. The point is that to use Fentons on a six, you have to use a donut gasket to allow the exhaust pipe (the pipe from the header to the muffler) the ability to move a little. The donut gasket allows that to take place. As I said, if for some reason the headers you have are flat surfaced on BOTH of the headers, there is a flat surface doughnut that is made and can be used to allow the head pipe to be attached by being flared and ride on the doughnut gasket with the pipe being held by a pull up flange, not a bolt up flange. That arrangement allows some movement for the head pipe and allows everything to be slightly "loose" instead of rigidly tight.
Again, I will say, experienced exhaust installers know what I'm telling you to be the best way to install these type of dual exhaust systems. From the comments here regarding "other" ways to make the system function correctly prove that you can't just "bolt them up" and expect no problems. Mine have been on my truck as I describe here for 30 years with no problem. Right now if I had to move one of my head pipes over 1/4" because it was hitting the side of the oil pan rail, I could loosen the flange, move it over and retighten the flange and the head pipe would be over and stay over. The don't bolt up "tight". They need to run a little "loose".

Obviously, this guy had never installed pipes on Fentons.

To top it off, the studs the installer used were extra long and the pipes won't come off the truck so I had to remove studs to get the old gaskets out. Wouldn't you know, I broke a stud. I tried removing it in place with an EZ-out and heat but no luck. I've decided to pull the headers. I'll figure out something before they go back on.

Keep those ideas coming.

The doughnut TooMany2Count is showing is the doughnut that would go on the front header because it doesn't have a beveled outlet. The doughnut slips right into the header opening and the bottom rounded part will fit nicely into a flared exhaust header pipe. The flange pulls up on the flare and will hold it together. The beveled header opening has a doughnut that looks the same except the rounded off part, like the bottom of the doughnut TooMany2Count shows, is the same on the top. A flared header exhaust pipe is also used with a flange to pull it up.

Shoddy workmanship. One of the flanges was badly warped. They both had ragged edges of pipe sticking through the flange keeping the header from seating. Neither flange met the header squarely and when one is in place the other was off. (They are welded together at the muffler.)

The header surfaces were machined smooth but there were some tiny cutting tool marks. They probably wouldn't matter but I smoothed them anyway using 220 grit on my table saw table. I then went to 320 then crocus cloth.

Then I went to work on the pipe flanges. I first dressed them down with a vixen file to get the ragged pipe edges off. Then I used a method suggested by Bill M. (Thanks, Bill.) I used a piece of steel plate wrapped in sandpaper. I started with 100 grit, ended with 320. It took at least 2 hours to get the warped one trued. The other took less than an hour.

Then I put the manifolds back on using the hi-temp silicone sealer. (Thanks for that tip, Greg H.) Even though there was no evidence of leakage between the manifold and head I suspect the intake was sucking air there. I had to run part choke. I hope this fixes that.

Next I did Tony P's trick to stress relieve them. (Thanks, Tony.) I bolted them up without a gasket then heated about a 2" strip on each pipe red hot and let them cool overnight. I haven't pulled them loose yet so I don't know how successful it was.

I found a gasket that I think will work. It is a Fel-pro 60052. It is for a 1949-67 Ford. It has a metal crush ring around the hole. But I had to order the other one. Out of 4 parts places in Mineral Wells there was only one of these gaskets.

I think there is enough flex in the mounts that they won't be a problem. I think with the other problems I found and corrected this ought to fix it. When I put the engine back in last month I used new mounts so it shouldn't be flexing much anyway. I hope.

Thanks for everyone's input.

All you gotta do is give Cletis a reason and then you had better stand back!!

I don't get it. Why not (if possible) machine the bevel in the Fenton header(s) to accept the donut and would all this be a non issue? As explained the donut is very forgiving and allows for angular misalignment while completing a seal.

That could easily be done, Curt, but why not use a flat doughnut on the front header and a beveled doughnut on the back one. Both react the same to any angular misalignment with ease the problem is solved. The other thing about doughnuts is that they can be reused. There really is no issue here if the muffler shop knows what the heck they are doing before they start the job!

I just received my headers and dual pipes from WALDRONS EXHAUST .I posted pictures on my photo bucket if you wanted to look.

Here's a follow up to this old post. My fix detailed above worked. I now have over 25,000 miles on the setup with no exhaust leaks.

A clarification on the procedure: when I stress relieved the pipes I heated them about a foot away from the flanges.


That would be a great plan if one was starting from scratch. I already had about $500 invested in pipes with flat ends. As Joe stated, one of the Fentons already has a bevel. You would only need one cut. Then have flared pipes installed.