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Header exhaust leaks

3bals

3bals

Retired Firefighter
Messages
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297
Location
Minnesota
I'm being plagued with header leaks on my custom stainless headers on my P-400 upgrade in my Motorhome.

Originally we used stock exhaust gaskets, but the bolts would loosen some would even back out far enough to fall out. We talked to Peninsular to see what they recommended and they said to use high temp RTV and regular header bolts. We did that, but used locking header bolts. Well that lasted about 500 miles before blowing out on at least 3 cylinders.

Next we will check the headers for straightness and try to figure something out.

Thoughts?

Here's a pic of the headers header 1.jpg
 
Headers need to be re-torqued after so many miles. My Dodge with an aftermarket manifold had trouble with the gaskets crushing and loosening things up. I used better gaskets.
 
Stainless moves around really bad with heat, very very few exhaust mannies are made with SS for this very reason...

Be warned if you do use the stage 8 lockers be ready to have broken bolts a short time later...
 
SS is common as dirt for the Cummins. :confused: Maybe why I had some trouble at first with the AFE 46-40011 BladeRunner Stainless Steel Exhaust Manifold .
 
sctrailrider said:
Cast SS yes, tube ... not so much...
Click to expand...

I been thinking about the expansion. I always assurmed they have been making this type of header/manifold. Have they?

Yes that 1 large tube could grow in length with heat and try to spread the 4 ports apart from each other. The thicker the pipe is the more it will resist growth.

But do not to think stainless pipe is worse than steel. We had to use stainless in making pyrolysis chambers subjected to amazing heat. We made small test units out of steel that would fail under flame after only a couple hundred hours. Stainless can deal with it for years. The mistake most people make is over estimating the stainless ability, so they make it out of too thin or wrong type of stainless. 410ss actually expands slightly less than cast grey iron. But it is more expensive than 304 or 316. Cast grey is what blocks and heads are made of and is what they should have used.

Ask them if they made this type Of header before and what type of stainless it is, along with thickness. Thinking about it, boats tend to run water cooled manifolds a lot...

If they're still on the rig, take a very accurate measurement of the length while cold then get the truck very hot (high EGT) then take another measurement right then.
 
Last edited:
But DON'T melt your tape measure or burn your fingers trying to measure that hot header!
 
We used those locking header bolts one week ago today with high temp RTV, no gasket. Like I said, it lasted about 500 miles before blowing the RTV out. The bolts stayed tight.

Yesterday I spoke to a machine shop about milling the flange surface. They were somewhat reluctant because taking material away from already thin flanges. We talked about what type of gasket to use and what is causing this.

Heat, stainless bolted to iron and possibly the fact that I wrapped the headers before installing them when the engine was new holding the heat in.

Possible fixes. Remove the headers, check them for straightness, unwrap them, find a quality gasket, use high temp RTV on both sides of the gasket an the locking bolts. Luckily, I have an extra set of heads to make sure all fits before reinstalling the headers.

Now the hard part is finding a quality gasket.
 
Use copper like the racers do. On a completely unrelated topic, Jody, your homemade sauerkraut ROCKS! Tried some of your hot batch on some jalapeno cheddar brats with honey dijon mustard, yum! Put some of your regular batch on some bacon cheddar burgers with spicy brown mustard, da bomb! Paired those up with some New Belgium Brewing's Voodoo Ranger Imperial IPA (9%ABV) to wash it down, fantastic!

If ready-made copper exhaust gaskets are not available, you may need to cut your own from some sheet copper.
 
Also, sorry I wasn't in Lincoln over the weekend to watch the total eclipse with you and Connie, as I was already out in the Panhandle to watch it from Carhenge. Perfect weather, 2 minutes 28 seconds of totality and it was one of the best places in the U.S. to view it from. For those of you who don't know what Carhenge is, Google it. You'll see why people drove from as far away as NY, NJ, FL, NM, CA, TX and Alberta and Ontario Canada to watch the Total Eclipse from there.
 
Those header flanges should be minimum 3/8" thick. Anything less will warp. If they're not 3/8", ask Peninsular why, and if they'll remake you a proper set of headers with the right flange thickness. Also, a single piece flange, instead of individual runner flanges, will be much more stable. If you go the soft copper route for gaskets, do NOT use any RTV. In fact, the RTV may be the problem with the current set up.
 
I'm not having much luck finding after market gaskets for the 6.5L TD. Are they the same as a big block w/D shaped holes? 6.5L head.jpg
 
No they aren't, What Husker said about needing a full flange is correct and is part of the problem, but getting them to admit that isn't going to happen... we all know gaskets don't stay long on our stock mannies, they sure aren't going to stay with separate flanges I don't think... but I know you are searching for what will work...

I have seen copper gaskets for ours on ebay....
 
There is someone in AZ that makes copper gaskets, I don't remember their name, they are on ebay, at one time I talked to them and they said to send them a gasket and they could make a set... the seller has lots of listings on the bay...
 
You can always get the OEM GM one piece gasket and trace it out on a sheet of copper then cut out a set.
 
I know a lot of people swear by rtv there. I have never had good results.
When 6.5 manifolds or hummer headers wont seal up bare,
I use : Felpro ms 91587
 
I have a large 6" belt sander my dad used in his wood shop, it's great for running the flange across to make them flat, the entire mannie will fit against it so it all gets nice and flat...

If you feel the need you could send them to me and I'll swipe them for ya, a machine shop may not be as cheap as shipping would be.. just offering ...
 
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