I guess it would not hurt to try a sealer. I would have my doubts but since at least you know you won't be breaking bolts off it won't be that difficult to try. I would try that what is it orange or red? Made for headers. I think I would be tempted to try the just snug it up and let it partially or maybe fully cure? Then torque it down? And maybe give it an extra day or two to really cure to give it the best chance? But with the turbo adding back pressure and heat kinda seems like a long shot.

If you are willing to spend a few bucks which it sounds like you are if you are considering a new head maybe try ordering a few other brands of gaskets to get a good look at them and maybe one will look better to you as far as how it would crush and seal in the problem area? I know I have been very unimpressed with most exhaust gaskets. Need to find a source for atomic lead infused asbestos.

Normally I try not to use exhaust gaskets but that only usually works when you can have both sides surfaced. I think on my last used engine swap I wasn't able to find anyone to surface the manifold and my mill isn't that big so I'm pretty sure I used the gaskets out of the fel pro full gasket set and I may have used a bit of the red or orange sealer just for fun but maybe the mess I'm remembering during the install was anti seize? I know I made a mess trying to get bolts started and gaskets in place.

 

This may sound a little bit hilly billy, but ...

I'd use transfer dye (Dykem, white spray paint, etc) on the head and/or manifold to find the contact points on the manifold and GRIND THEM OUT. This should allow better contact and uniform clamping pressure across the entire gasket. Yes, I'm suggesting wrecking your spiffy new manifold face with a bunch of cut-n-try "tuning."

"Back in the day," my MC2 Audi engine had the 100%-assured crack on the 3-2 collector of the iron manifold. Had a qualified buddy help weld it (pre-heat,peen, nickle rod, post heat, insulated slow cool etc) with great success--lasted thru my ownership. Had a different buddy face the manifold, "must be uneven after the welding." My "new" perfectly-flat manifold mated poorly with the uneven factory aluminum head surface.

Someone who's tested or read up on it could suggest the drive pressure in the hot side of the exhaust assembly, but I'd think it must be 25-50 PSI--which would be quite leaky.

Y pffft pffft pffft MV

 

I believe the gm-x turbos are 2:1 drive to boost pressure, so its probably around 25 psi in the exhaust. Not a lot but more than some rtv can handle. I do like the dykem idea, I could even build up a little with some weld on the manifold where the low spot on the head is. If I can't get it to snug up I'll give that a shot.

 

I snugged up the rear manifold bolts and the crossover bolts. Got a quarter turn out of the rear two manifold bolts and quite a bit on the crossover flanges. Its quieted up for now, we'll see how long it holds.

Gotta say it really is such an improvement not having an exhaust leak. Way more power, lower engine temps, better mpg. I bet this problem is a lot of why these things have such a poor reputation. The noise isn't to far off the regular idi rattle and you cant see it without taking an awful lot off.

 

Does anyone know if the diesel trucks had additional sound insulation added? I know back in the 80's if you got a diesel Cadillac you got a bunch of insulation so you could barely hear the engine. If you swapped in a gasser you really could not hear the engine at all.

 

I know my 95 and 99 have a sort of insulation on the engine side fire wall that my 94 and 95 gas trucks didn't have. I don't know what the cabin side fire wall had on those trucks. I never had them apart far enough to see that. I know when I pulled the dash out of my 95 6.5 part of that insulation crumbled and fell off. The engine was louder after that then when it was there.

 

Diesel models got underhood insulation blanket too. I'm not sure if all gasser models got the blanket but I have seen two different versions, the diesel one is thicker.

Steve

 

Leak is back and better than ever, while the bolts are still tight. I've ordered a sheet of remflex gasket material and I'm going to try cutting out my own gasket. This stuff is supposed to offer a 50% crush and starts at 0.140", so it should be plenty to fill in some pitting. Being graphite I hope it will sorta mold itself into the pitting, but we'll see.

I do still plan on comparing the surfaces using the dykem but unless I can get a 60 thou feeler wire between the manifold and head I don't think I'll be doing any more grinding.

 

I'll be keeping an eye on this. I also have some leaks developing. Not bad yet.

 

Luckily for me its just leaking between the turbo and the downpipe. Nothing between the head and manifold as best as I can tell. Recent drop in mpg must be due to something else. I do think the remflex would work nicely, it has a lot of crush and seems pretty easy to cut with a utility knife. I will probably make the gaskets and put them in when I swap the turbo just so I don't have to think about it, but the regular gasket seems to be holding for now.