Z28 exhaust manifold crack opinion

[rszmjt]

Originally Posted by mhm1966

Kevin,

I am glad you are using welding material for the USA. The stuff made in China is junk and will never provide an adequate weld. You should also make a jig to mount your exhaust manifold in so that when your done welding the holes in your exhaust manifold lineup with the threaded holes in your head.

Chances are you will have to drill the bolt holes out a little bigger on the end cylinders #1 & #7 anyway, those style manifolds always seem to shrink in from heat.

We used to see that sort of cracking on similar design exhaust manifolds from mid 70,s Chev trucks that had propane conversions.

[KevinW]

Originally Posted by mhm1966

Kevin,

I am glad you are using welding material for the USA. The stuff made in China is junk and will never provide an adequate weld. You should also make a jig to mount your exhaust manifold in so that when your done welding the holes in your exhaust manifold lineup with the threaded holes in your head.

Hmm, that might be tough. I have to cool this down slowly, so overnight in a bucket of sand is the ticket.

I have been working on the smog tubes and the un-cracked manifold. Once done with that I plan to switch to the nickel MIG wire and try it out.

[KevinW]

Originally Posted by rszmjt

Chances are you will have to drill the bolt holes out a little bigger on the end cylinders #1 & #7 anyway, those style manifolds always seem to shrink in from heat.

We used to see that sort of cracking on similar design exhaust manifolds from mid 70,s Chev trucks that had propane conversions.

Thanks for the tip. I will test fit the manifolds and see how they fit before welding. I can always hit the bolt hole with a die grinder.

[rszmjt]

Originally Posted by KevinW

Thanks for the tip. I will test fit the manifolds and see how they fit before welding. I can always hit the bolt hole with a die grinder.

Very hard to die grind that length of hole, just use numbered bits and drill it slightly larger till bolts go in if the manifold has shrunk.

[bergy]

Most of you probably know this, but there was a repair station at the Tonawanda Foundry for cosmetic welds on cast iron parts. These repairs could only be done on non-stress areas though. The repairman just heated the damaged area to cherry red with a torch - then welded the damaged area - then covered the repair with asbestos cloth. They left the asbestos on until the next day before grinding the repaired area smooth. Most of the repairs involved chipped valve cover rails on heads and intake mating surfaces on the front and back of blocks.

[KevinW]

OK, sorry for the delay. Family stuff came 1st in priority

So I wanted to fill a hole in a riser for a blank. Here are the pics. Had some feed issues partway through, so some crappy welds. But good news, a cutoff wheel took the welds down with no issues.

Did a dollop of weld right on the cast surface (previously media blasted). Could not pry it off. Then did some grinding and smoothed out nice without any cracking that I could see. Did some chip hammering and it dented easy.

Then I filled the hole, no pre-heating of cooling. That amount of weld did not heat the part that much. Ground it smooth, easy-peesy

Next, will have to make a crack in a junk manifold, drill it and bevel and see how it goes.

[KevinW]

Alright! Lets work on an actual crack! On a test manifold

Drilled some holes at the end of the crack, but later saw it go further, so grinded past.

Cut a groove and ran a bead. Then put it in some media to slow cool it.

My feed issue is fixed, but I was not centered in the groove and it missed one edge. But still weld stuck well in the groove IMO.

Will still need grinding and some more passes, but I am happy with the result. Pinged it with hammer and it rang well.

I think I will next fix the smog manifold over the weekend and finish this test one up after.

[KevinW]

Well, that was a FAIL! Weld looked nice but did not adhere. Ground it flat, hit the edge of the manifold and the cracks appeared. Well this is why we test

Did the first pass over an inch, too much probably. Next test will be 350 deg preheated, only 1/2 inch passes, then stress relieve, then back in the heat. Also instead of 75% Argon, I will be going full Argon and bumping up the heat range of the welder.

[frankk]

What are you doing to stress relieve?

[KevinW]

No stress relief, just welded and stuck in media to cool. It was a test next test will include relief with pick hammer.