Exhaust manifold crack
Race Director
Joined: Oct 2000
Posts: 12,687
Likes: 3,139
From: Shamong, NJ
If you buy a used one, look it over carefully, it's pretty common for the 70's "ram horn" manifolds, to crack in that area.
Dorman makes a decent replacement that sells for about $100 each, and exact repros are about $240.
Dorman makes a decent replacement that sells for about $100 each, and exact repros are about $240.
Safety Car
Joined: Jun 2004
Posts: 4,652
Likes: 80
From: Lakeland Florida
Time to buy a reproduction one. Yours may be able to be welded, but if this is not a concours or frame off reproduction, then store the old one for future use, and get a replacement one.
kdf
kdf
2026 Loser of the Year
Joined: Sep 2013
Posts: 36,607
Likes: 7,053
From: New Or-leens Loo-z-anna
Back in the day "V-ing" a crack......preheating the cast part.....then using a stick welding rod of the same material to weld the V closed....then slowly bringing the part down to room temperature was a sure-cure.
Melting Slicks
Joined: Oct 2013
Posts: 2,569
Likes: 126
From: San Diego California
That crack's gotten pretty big Jeff. You now have a great excuse to tell the wife it's time to get a set of headers! 
After all, they flow better and are soooo much cooler. A lot of people know this, which is why the market is full of these ram horns.
Good luck.
Steve
After all, they flow better and are soooo much cooler. A lot of people know this, which is why the market is full of these ram horns.
Good luck.
Steve
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Michael S. Palmer
Le Mans Master
Joined: Dec 2007
Posts: 6,422
Likes: 591
From: McHenry Illinois
Good excuse to get a set of side pipes!
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,118
From: Crossville TN
No doubt in my mind that the heat riser valve on the outlet of that manifold was stuck in the 'closed' position. Driving it that way builds up IMMENSE heat. I had one that did so and it 'ballooned' the metal out (bulging) which meant it was close to melting temps for cast iron! 
You might be able to repair it with brazing (can't weld it); but that depends on the width of the crack and your welder's skills.
It would be best to find a replacement.
And make sure that heat riser valve is working properly...or just cut the valve plate off the shaft and NEVER worry about it again.
You might be able to repair it with brazing (can't weld it); but that depends on the width of the crack and your welder's skills.
It would be best to find a replacement.
And make sure that heat riser valve is working properly...or just cut the valve plate off the shaft and NEVER worry about it again.
Thread Starter
Instructor
Joined: Mar 2015
Posts: 203
Likes: 4
From: Dallas Area Texas
yes that thought crossed my mind... but I don’t want the expense of redo-ing the rest of the exhaust system piping.
Thread Starter
Instructor
Joined: Mar 2015
Posts: 203
Likes: 4
From: Dallas Area Texas
No doubt in my mind that the heat riser valve on the outlet of that manifold was stuck in the 'closed' position. Driving it that way builds up IMMENSE heat. I had one that did so and it 'ballooned' the metal out (bulging) which meant it was close to melting temps for cast iron!
You might be able to repair it with brazing (can't weld it); but that depends on the width of the crack and your welder's skills.
It would be best to find a replacement.
And make sure that heat riser valve is working properly...or just cut the valve plate off the shaft and NEVER worry about it again.
You might be able to repair it with brazing (can't weld it); but that depends on the width of the crack and your welder's skills.
It would be best to find a replacement.
And make sure that heat riser valve is working properly...or just cut the valve plate off the shaft and NEVER worry about it again.
ill be ordering a new manifold.