Hi guys,

My 250 came with a set of Clifford long tube split headers. I've noticed that the area where the tube comes through the mounting flange is not very wide in spots, from 1/8" to 1/4" wide and in fact, the mounting flange is blackened where there was an obvious exhaust leak in the past.

I'm thinking that the best way to resolve this is to grind the tubes back flush with the mounting flange, TIG them to the flange, and file flat. I think this will give me the best sealing surface. Alternatively, I could TIG some weldment to widen the area and leave the configuration as it is, with the tubes sticking through the mounting flange and being flattened out about 1/4" wide and about 1/16" thick on the inside of the flange.

Thoughts?

However

Is this the flange to the head?

Yes. The 1 1/2" diameter round tube goes through the flange and is stretched into a rectangle (exhaust port size) and bent over on the inside of the flange on the mating surface. I was in a speed shop today and noticed that some of the V8 headers had fairly wide flat area...about 1/4" inch which would give a nice tight seal I'd think. Mine goes from 1/8" to 1/4" and when I lay the exhaust gasket on it, there are a couple places where there is barely ANY overlap which accounts for the previous exhaust leak.

I think what you have found is the reason tube headers are notorious for not sealing. I tried to straighten the headers I have on my 292 now by grinding down that area on the flange. That area is the weld and if you grind too far you have little or nothing holding the tube on depending on penetration. I have another set of headers to replace the ones I ground. 8-[ I'm thinking of doing what you have already thought of. I'm going to try and MIG some more material around the existing weld and then flatten with a belt sander. If someone has a better idea I'd sure like to hear it.

Larry

i LIKE TO PUT SOME INSURANCE WELDS ON THE OUTSIDE SIDE OF THE FLANGE - NOT ALL THE WAY AROUND, ONLY 1/2 " AT THE TOP AND BOTTOM AND SIDES. Then I take them to a shop with a BIG belt sander used for resurfacing cylinder heads and make them flat. You're right about the headaches though. That is why I run split cast exhausts on the street with NO gaskets.

I read in one of the metal working books that some people braze a big fillet on the outside where the tube goes into the flange. The brazing rod is a little more flexible than the welding material, and has a sort of natural wetting action that makes a good seal. The down side is that once you braze something it can't easily be welded again. The upside is if you do it right it would look really nice (I used to build bikes this way back before everything became carbon fiber and titanium)

Leif

I've thought about brazing, but didn't what other problems it might cause particularly for coating, paint, plating, ceramic. What about building up around the weld on the inside of the flange? IIRC there isn't any way I'm going to get a good seal with the new headers and the gasket. I'd also like to match the port a little closer from head to headers IIRC I couldn't.

Larry

What I ended up doing was TIGGING additional steel rod around the narrow bead...making it at least 1/4' wide. I then knocked the proud down with a hard sanding disk and marked it up with a wide tip sharpie. Then with a large file, I filed both flanges at the same time...that is, I kept the file in contact with both flanges at all time...and kept filing until all the sharpie mark was filed away. Should be nice and flat.

On the head side of the flange there should be some weld thats been ground flat but not to the flange.This would be on the face of the header flange that contacts the manifold gasget.That weld is ground flat but still raised from the flange to aid in sealing.There should be a bit of weld thats been ground to contact the gasget.Don't belt off all the weld to the flange face or you will have seal problems.

get a set of cast iron headers from Stovebolt at theboss@stoveboltengineco.com Phone # 586-739-9601 part # 42-0070
price was $259.00 probley more by now. I have a set and have had no problems with the, I get them in 2000.

I agree with xderelict about the weld.

Try different gaskets. Replace the end pins with studs if it still has them. Use the cheapest gasket you can find and don't over-tighten.
I originally tried a three-piece Felpro that cost $30. It lasted a week and a half. In the last 15 years I've had two cheapo $6 gaskets on it, replacing the first, five years ago with the engine rebuild. This last one leaked a little at first because I over-tightened it. I think mine are Heddman