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#31
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I'll pass along what we used to do at the mill when working with super hard brittle material. Try peening the weld with the pointed end of a chipping hammer. Just keep hitting it until you figure the entire weld has been gone over. Then do your slow cooling. It worked for us. Good luck
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#32
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I am giving up on this Pre-heat, small welds, peening, slow cool. All did not work. So disappointed. Anyone have a non-cracked 3942527 manifold they are not using?
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69 SS 350 convertible (in peices) 69 327 convertible (driver) |
#33
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FWIW the exhaust manifold with the "raised walls and rivet bosses" for the preheat shroud and without the provisions for smog are not correct for any 69-73 Z28.
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~JAG~ NCRS#65120 68 GTO HO 4 spd Alpine Blue /Parchment 2 owner car #21783 71 Corvette LT1 45k miles Orig paint - Brandshatch Green - National Top Flight - last known 71 LT1 built. 71 Corvette LT1 42k miles Original paint - Black - black leather - only black LT1 known to exist. NUMEROUS Lemans blue Camaros, Monza Red and Daytona Yellow Corvettes & a Chevelle or two... Survivors, restored cars, & other photos https://picasaweb.google.com/lh/myphotos |
#34
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I had a similar crack on a small block manifold but was on the portion that bolts up to the header pipe. I never repaired and had no issue with it all.
I have about quit messing around with 50 plus year old exhaust manifolds and have been purchasing the repros. The casting numbers in most cases are correct, and the date code can't be read when the manifold is on the car and its nice to have a part that has not heat cycled dozens of times. Just my .02 worth.
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65 Corvette Coupe L78 67 427/390 Vette Coupe unrestored 67 L-79 Vette roadster (Top Flight) 69 L71 Roadster Survivor 69 L46 Roadster Survivor (Sold) 69 Z/28 RS 69 Dodge Charger R/T 70 W30 442 Auto Air Survivor 2016 Z06 Coupe M7 70 AAR Cuda (Sold) 69 L78 Chevelle |
#35
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Quote:
Buying a repro might be the way to go now and just use the one original side that is still good.
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69 SS 350 convertible (in peices) 69 327 convertible (driver) |
The Following User Says Thank You to KevinW For This Useful Post: | ||
firstgenaddict (08-30-2021) |
#36
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Thanks - I kept thinking to myself "I swear the crack was not near that bad".
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~JAG~ NCRS#65120 68 GTO HO 4 spd Alpine Blue /Parchment 2 owner car #21783 71 Corvette LT1 45k miles Orig paint - Brandshatch Green - National Top Flight - last known 71 LT1 built. 71 Corvette LT1 42k miles Original paint - Black - black leather - only black LT1 known to exist. NUMEROUS Lemans blue Camaros, Monza Red and Daytona Yellow Corvettes & a Chevelle or two... Survivors, restored cars, & other photos https://picasaweb.google.com/lh/myphotos |
#37
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The only alternative I can suggest is brazing the crack. Braze, while not as strong as weld, is pretty forgiving for cracks on cast iron since when the cast iron cools it will "stretch" to the surrounding shrinking iron rather than pulling the iron. You can ceramic coat it afterward to cast iron color (I've had good luck with Cerakoat Glacier). I've seen punch press frames brazed together that have lasted for years afterward. The manifold would be much less stress than that. Typical heat on the manifold is less than the melt point of braze. Maybe worth a try.
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70Z28 04B Norwood Forest Green-white Stripes Black DeLuxe Interior Owned since 1978 - First Car Last edited by BCreekDave; 08-30-2021 at 12:35 PM. |
#38
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Thanks Dave. I think I have some brazing rods left over from another project to test that. What can it hurt?
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69 SS 350 convertible (in peices) 69 327 convertible (driver) |
#39
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Kevin, there is a guy up near me that knows how to weld cast iron. His name is Steve Babinsky from Automotive Restorations ([email protected]) (908) 236-6400. His cars go out to Pebble Beach. You might want to talk to him about the cast iron weld. He told me the cast iron welding rods you buy are from CHINA and are junk. He has his welding rods made here in the USA.
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#40
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OK, I said I was giving up, but I just can't let a smog manifold go unrepaired So was doing some other tests and welding different cast iron stuff.
The "special" nickel wire was just not sticking to the parent metal. So in the "what the heck" moment, I just used the regular .025 mild steel wire. It seems to stick much better and don't see a join crack (yet). So I went ahead and did the smaller of the cracks on the smog manifold. Its heat and clean 1st. Then when warm to touch, small beads, and grinding, then another bead and grinding, etc, waiting for it to be warm to touch each time. Seems to stick properly. Finished it up with some die grinding and media blast. I will let this sit over night and then heat it up with a torch to see if any cracks appear. Not sure why I am getting the voids, I ground them out between welds. I found after the first beads that if I start the weld on a grinded bead it flowed to the cast iron better than starting on the iron. I will work on the mating surface more if and when I do the 2nd crack. That will get a gasket anyways. Opinions welcome as always
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69 SS 350 convertible (in peices) 69 327 convertible (driver) |
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