What to do with Warped Exhaust Manifolds?

[Peter_Crowl]

Since I have a warped manifold that's leaking exhaust, and will have to R & R it to do a repair I thought it best to look into the alternatives...aftermarket headers being one of them.

Still not sure how to address the problem - but address it I must.

Peter
in Denver

[fgutie35]

Peter, how do you know is the manifold that is warped?

[Peter_Crowl]

Well - I have not yet removed it to verify but...
It's blowing out on the right rear cylinder
It's as tight as it can get
From everything I read that's indication of warp

There seem to be as many opinions on this subject as there are people with 454's. But consensus is that the stock manifolds in this application are prone to warp.  People have planed them, used multiple gaskets, copper gaskets, Brian's guy suggests slitting the manifolds and using nothing but Never Seize compound .....
Then there's the Header group. Seems as though the experience of people who have installed good headers has been positive both in terms of preventing further leak and warp problems and in terms of increased performance/mileage.

All this to say, if the manifold has to come off - and it does - it seems wise to explore the options. Doing the job will be unpleasant enough. Having to do it again would be downright irritating.

[bluebird]

What ever you do, DON'T use double gaskets on it. I have a couple of GM service manuals, they both recommend cutting the manifold to help the warping problem. My old Itasca had warped manifolds. I removed them and got a large file. Filed them flat again and used a gasket made by felpro for the 454. Problem solved. I personally don't care for headers on anything but a racecar. But I won't try to talk you out of them. No matter which way you go the under bonnet temps will be very high. If you go with the headers you will have to replace the plug wires as the stock type will burn real quick. They probably need changed anyways. I know a fellow that took his manifolds off, had them milled flat and used the red high temp silicone for a gasket. He only has a few thousand miles since, but it isn't leaking yet. I use it on my race car headers all the time. Hasn't burned out yet.

[GWINGER]

If you use headers, buy  the good ones and the locking bolt system.

[Mississippi Winne]

If it is just warped, get it resurfaced so it is perfectly flat and have them slit between the bolts at a machine shop.  You shouldn't have to replace it again.  Likely cost more than the new one I showed you though.

Brian

[wrolandhyattjr]

While I don't have long-term results to report, I had Gibson headers and exhaust system installed at Camping World.  It was a compromise as the Banks was too rich for my wallet.

[fgutie35]

If I'm not mistaken, when the manifold warp, they tend to warp at the middle section. In your case, your leak should have come out from ports #4 and 6. The reason why I asked you how did you know, is because I had a leak exactly at the same port #8 as you. Like you , I jumped the gun and began to study all of my options and considered headers as well. I also looked at other aspects of actually doing the job myself and what was involved. At first, I looked at the cheap route which would be to remove the manifold in question, and have it re-surface at a machine shop, so I tought it was going to be cheap until I read that the bolts are pretty prone to break when trying to remove them, which besides being a head acke was a concern if I had to end up towing the MH to a shop to have them remove the broken bolts and re-do the treading; which already sounded very expensive. Well I was going to leave that project alone for the following summer, but then I decided to continue on a previous porject that I had started but not completely finished. On my quest to remove the A.I.R. system, I had already remove the air pumps, air valves, hoses, and canister, but I had not remove the pipes that come out from the exhaust manifold, which are attached by a 7/8's nut. Well I began with the more accesible one which happens to be port #8. I noticed that the nut was too thight to remove with a regular 7/8 wrench so, I decided to use a pipe wrench and just go at it. When the nut finally gave up, I noticed that part of the pipe was moving with the nut then I heard a snap. After closer inspection, I noticed the pipe was already "cut" or rotten near the nut except for a section about 1/16" thick which was the part that made the snapping sound. Well to make story short, I finished removing all of the other nuts by cutting the pipes first and then using an impact wrench which made the job a lot easier and faster. I plugged the holes with oil drain plugs that are M22X1.5 pitch in size, and put some cold solder on the treads to completely seal the deal. Well to my surpise, after I let the poxy dry, I turn on the emgine and notice there was no more leak noise coming from the manifold. So if you have the same problem, I would suggest to look into that first, before expending hundreds of dollars.

[Mississippi Winne]

I have a similar problem and was trying to figure out exactly where the leak was comming from.  I could hear it was comming from the rear of the motor so I tried using a funnel as a hearing aid to pinpoint the problem.  That was no help so I decided to stick my hand down there and see if I could feel the gas comming from the exhaust leak.  I felt it immediately and on closer inspection noticed that someone had put a gasket in there and part of the gasket had blown out on the last cylinder.  Now all I have to do is remove it and replace it without the gasket.

Any pointers on removing it without breaking the bolts?

Brian

[ClydesdaleKevin]

Every time I have ever removed exhaust bolts and manifold bolts, no matter how careful I am, no matter how much PB Blaster I use, no matter how much heat with a torch I apply, invariably at least one, and usually most, of them break.  Maybe I have bad luck, but they always always break.  When possible I'll use a nutcracker, but of course you need a lot of clearance, which you never have with manifold bolts.  Wish you a lot of luck!

Kev

[fgutie35]

I heard on another forum, of a process that is lenghtly (several days) and involes from WD-40 to some sort of vivration machine. The concept is to weaken the bond between the bolt and the head using every available means. It went something like this: bathe the bolts with WD-40 for two days, heat the bolts with torch, then use a hammer drill or air hammer to hit next to the bolt to create vibrations inside the head. Then try to remove by constantly heating and banging on the metal. Obiously, is a two or more man job, so I discartered as a plan. Plan B is to take it to the professionals and let them stress about it and just take it with Vaseline when the bill comes.

[Mississippi Winne]

I am a bit lucky in that my exhaust manifolds are stainless.  The manifold bolts are the Allen head racing type so maybe they won't break off.  If they do I'll just remove the head and take it to a machine shop to get the bolt removed. 

Brian 

[Peter_Crowl]

Finally got it sealed up. Had the manifold on and off 5 times.
Wound up replacing it.
Replacements are not easy to come by. Chevrolet/GMC Truck cannot supply them. NAPA lists one  - but none were in Denver. I got a Dorman from my local parts house. Know that the Dorman is a real POS. I had to die grind the casting to get clearance for fasteners...drill out the AIR rail ports so the tubes would go in...the manifold heat riser actuator no longer had clearance so I had to remove it...the mounting surface is not all that great so I used a Fel-Pro graphite gasket with SS port sealing rings. Hope that doesn't blow out.

It's as it they took a manifold and used it as the mold plug. Everything is off size by just that much.

But it's tight. Now we'll see for how long.

[ibdilbert01]

remove the head and take it to a machine shop to get the bolt removed.

Might want to try an "Easy-out" first, that vaseline the bill comes with can get messy.