New exhaust manifold for 180-190-190XT gas engine?
Printed From: Unofficial Allis
Category: Allis Chalmers
Forum Name: Farm Equipment
Forum Description: everything about Allis-Chalmers farm equipment
URL: https://www.allischalmers.com/forum/forum_posts.asp?TID=209502
Printed Date: 29 Dec 2025 at 12:14pm
Software Version: Web Wiz Forums 11.10 - http://www.webwizforums.com
Topic: New exhaust manifold for 180-190-190XT gas engine?
Posted By: DrAllis
Subject: New exhaust manifold for 180-190-190XT gas engine?
Date Posted: 27 Dec 2025 at 3:31pm
| 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. |
Replies:
Posted By: Allis dave
Date Posted: 29 Dec 2025 at 6:37am
| 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. |
Posted By: AC7060IL
Date Posted: 29 Dec 2025 at 7:59am
| 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. |
Posted By: DrAllis
Date Posted: 29 Dec 2025 at 8:04am
| 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. |
Posted By: AC7060IL
Date Posted: 29 Dec 2025 at 8:26am
|
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? |
Posted By: DrAllis
Date Posted: 29 Dec 2025 at 8:33am
| 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...... |
Posted By: Les Kerf
Date Posted: 29 Dec 2025 at 9:28am
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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AC7060IL wrote: