84 GN pseudo header manifold things

[GN_Guy]

From everything I've heard, the header style manifold things that GM put on the 84GN's are notoriously bad pieces of trash. I've had mine off and repaired nearly a dozen times - and I only street drive mine.

I remember talking to the folks at Kirban's a long, long time ago and they said that they had the best luck with putting a single cut in the flat piece of steel that runs between each of the ports and then powder coating them.

Apparently the cuts help keep the expansion of one port from putting stress on the others. The powder coating reportedly helps with heat distribution (uniform heating of the whole piece rather than hot spots).

Are there others that have had the same experience???

Are the 85's the same? I know the whole system is different on the 86/87's.

Does anyone have more info on a reliable fix???

Has anyone found a suitable replacement aftermarket system???

[pfredricks]

Originally Posted by GN_Guy

putting a single cut in the flat piece of steel that runs between each of the ports and then powder coating them.
Are there others that have had the same experience???

I've had that experience. My 84's were cracked, had 'em welded and added the cuts, all is well after 5000 miles as far as I can tell. But I didn't powder coat them. I haven't looked closely since the rebuild, but somehow the motor is still strong despite the owner's stupidity.

Originally Posted by GN_Guy

Are the 85's the same?

They are. I bought an '85 motor that I'm building now. This one had the header cracks also. I'm not sure about the cuts, I can't see how they would help given that the flange is bolted to the head.

I plan to have Lo-Ko put their coating on the headers, crossover and down pipe.

[GN_Guy]

Hey - Thanks for the info Paul.

Nice to know that the cuts seemed to help you. Where did you put the cuts exactly?? Is the placement critical, or just somewhere between will do?? What's the story with Lo-Ko? Do they specialize it that kind of thing?

Next time I have a couple days with nothing else to do, I'll yank mine off again. I'll also check with you again down the road to see how your set from the '85 do over time. It'd sure be nice to the the turbo boost gage go all the way up again!!

Thanks again.

[Keller]

Are both manifolds the problem, or just the driver's side primarily?

Is the driver's side the same as the 86/87 cars?

I believe that proper, quality welding can insure that the cracks don't reoccur. I had my 87 driver's side header repaired twice. And the second time really was part of a porting of both manifolds; I don't believe it cracked a second time. However, a good weld was put down in that area when beads were put down in all tube-to-flange areas. It was done by knowledgeable, experienced welders both times.

[pfredricks]

Originally Posted by Keller

Are both manifolds the problem, or just the driver's side primarily?

In my case it was both sides.

Originally Posted by Keller

Is the driver's side the same as the 86/87 cars?

I'm not sure, I haven't been able to conduct a side-by-side comparision. I've heard that the crossover pipe is different.

Originally Posted by GN_Guy

Where did you put the cuts exactly??

Through the flange between the pipes. In my case it was off to one side, but I don't see a need to position the cuts in any particular spot. Heck, I still don't understand how the cuts solve the problem.

Originally Posted by Keller

I believe that proper, quality welding can insure that the cracks don't reoccur.

This makes the most sense to me. Maybe a support on the crossover would relieve the weight load on the headers, or stronger pipe material....

[Keller]

Originally Posted by pfredricks

Maybe a support on the crossover would relieve the weight load on the headers, or stronger pipe material....

I've seen a gusset created for the rearmost pipe on the 86/87 headers before. Also, the Poston ones may be a thicker material. The TA ones are definitely a better grade of stainless.