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DrAllis 
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Joined: 12 Sep 2009
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 Topic: New exhaust manifold for 180-190-190XT gas engine?
Posted: 27 Dec 2025 at 3:31pm |
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I don't believe these are available at all anywhere, correct ??? If i'm wrong, please steer me in the direction where I might purchase one. So, assuming there aren't any available, I have plans to build probably two sometime this winter. They will be of 1/4" thick steel instead of cast iron and it shouldn't ever crack like cast iron does. If anyone is interested, let me know and I'll include you on my build schedule. Thanks.
Edited by DrAllis - 28 Dec 2025 at 10:11pm
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Allis dave
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Posted: Yesterday at 6:37am |
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A friend of mine was looking for a new 190 gas manifold a few years ago. He bought the tractor cheap with a bad manifold. He is a decent welder and finally repaired his becasue he couldn't find a replacement.
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AC7060IL
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Posted: 22 hours 52 minutes ago at 7:59am |
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DrAllis, maybe try welding up the OEM manifold? Problem isn’t the cast manifold, it’s the gas engine’s timing. Engine is set too lean, so it’s cylinder’s exhaust becomes a blow torch with flames pushing upwards thru manifold & out the muffler extension pipe? The high heat tempered manifold (+1500f) is cracking after engine shuts down & manifold cools to quickly? To remedy it, try setting timing 4-6 degree before OEM setting. That will enrichen it’s burn without any carb adjustments. It’ll cough some, but it’s Power will be fine.
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DrAllis
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Posted: 22 hours 47 minutes ago at 8:04am |
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Well, you might be right in theory, but you cannot time the ignition at anything faster than 25 degrees BTDC or the detonation will destroy the pistons. I know this factually from replacing broken pistons. I'm sure a good operator that lets the engine slow idle for a couple of minutes before shutdown would help reduce the castings cracking, but it's a known problem from back in 1964 up to the end. They made one manifold casting change (in the 70's) to try and help and I'm sure it did, but these days there's nothing new or good used available it seems. I'm beginning to wonder if i can even get the gasket that goes against the cylinder head. I'd rather start with new steel and fabricate something that I know will outlast a 50 year old casting that has been cracked and welded up as a repair.
Edited by DrAllis - 22 hours 34 minutes ago at 8:17am
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AC7060IL
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Posted: 22 hours 25 minutes ago at 8:26am |
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Right. Well then Ideally, a tuned exhaust header could suffice a lean engine. Tuned correctly, a custom header could scavenge hot exhaust while also improving power. Maybe a bit overkill though?
Are these “pullers” or farm tractors? Or both?
Two piece headers (1-3,&4-6) could remove heat even better?
Edited by AC7060IL - 22 hours 22 minutes ago at 8:29am
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DrAllis
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Posted: 22 hours 18 minutes ago at 8:33am |
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Just farm tractors. I've built puller manifolds out of the same materials without any failures, but admittedly the 1700 degree temps only last for 10 seconds and then cool down driving back to the pits. Anyway, this will be fine as any of these gas tractors aren't plowing and discing anymore. it's just nice not to hear constant cackling coming from the exhaust manifold. Sounds like Jed Clampetts truck......
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Les Kerf
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Posted: 21 hours 23 minutes ago at 9:28am |
 AC7060IL wrote:
...Two piece headers (1-3,&4-6) could remove heat even better? |
Two piece headers would probably be easier to fabricate, and with the low overlap duration of these camshafts there is almighty little to be gained trying to build any extraction/tuning into the design for a farm tractor. A great big ugly low backpressure exhaust will work just dandy. Your mileage may vary 
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Ed (Ont)
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Posted: 11 hours 5 minutes ago at 7:46pm |
Is this the 262 6 cylinder gas engine we are talking about? What was the compression ratio on these from the factory? Would be nice to run one of these on dyno and check the exhaust temps at 25 degrees and then give it a couple degrees more advance and see what the readings are. I set my WD45 about 2 degrees more than the "F" mark. Sure works nice and starts nice. But of course I do nothing with it except for a couple drives now and then. I remember at home on the farm we ran a belt hammer mill with it. Ran it almost wide open when we were doing that usually for about 2 hrs. Exhaust manifold was cherry red. But back in those days we did not use a timing light. Probably just didn't know any better!!!
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DrAllis
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Posted: 10 hours 42 minutes ago at 8:09pm |
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No. The 230-262 family came from Buda's line. The G-2500 (265) and G-2800 (301) were new Allis creations in 1964.
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JC-WI
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Posted: 3 hours 40 minutes ago at 3:11am |
Early exhaust manifolds 4020190 needed the inside hole on the outer EX ports drilled out 1/16 inch larger for the expansion and contraction. Manifold 4021866 (effective with One-Ninety gasoline engine number 2G-15618) had the larger hole in them. They used lock-thread capscrews on the intake and exhaust manifolds and torqued the two capscrews at the ends of the exhaust manifold to 30-33 ft. lbs. and torque all remaining capscrews 44-49 ft. lbs.
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DrAllis
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Posted: 58 minutes ago at 5:53am |
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And then, if I have my events in order, they changed the exhaust manifold casting shape making the bends from the front and rear exhaust ports straighter, to try and eliminate cracking.
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