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: 22 Mar 2026 at 4:20am
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
 |
AC7060IL wrote:Posted By: Ed (Ont)
Date Posted: 29 Dec 2025 at 7:46pm
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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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Posted By: DrAllis
Date Posted: 29 Dec 2025 at 8:09pm
| No. The 230-262 family came from Buda's line. The G-2500 (265) and G-2800 (301) were new Allis creations in 1964. |
Posted By: JC-WI
Date Posted: 30 Dec 2025 at 3:11am
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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. ------------- He who says there is no evil has already deceived himself The truth is the truth, sugar coated or not. Trawler II says, "Remember that." |
Posted By: DrAllis
Date Posted: 30 Dec 2025 at 5:53am
| 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. |
Posted By: AC7060IL
Date Posted: 30 Dec 2025 at 10:40am
| Maybe exhaust heat transfer for gas atomization would not be functional? But, what If a D2800/D2900 exhaust manifold was swapped onto a G2800 & then it’s gas muffler be modified to bolt in place of turbo(D2900)? |
Posted By: AC7060IL
Date Posted: 31 Dec 2025 at 8:27am
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Could an AC D2800/D2900 cylinder head be bolted directly onto an AC G2800 block? Maybe no cylinder head bolt alignment issues, head gasket issues, etc??? Reason I ask is that the cross-flow design of the diesels head should benefit the gas engine vs the OEM gas intake/exhaust manifolds on same right side of G2800 head. Maybe plug the Diesel injector holes & drill/tap spark plug holes on its left side where G2800 distributor is located? What are the chances a gas carb could be fabricated onto the D2900’s air intake & also accept its turbo for a modest 5-7 psi if waste gate was installed? |
Posted By: DrAllis
Date Posted: 31 Dec 2025 at 8:49am
| 2000-series blocks and heads all interchange without issue, gas or diesel. An updraft tractor type carburetor would be a challenge on the left side of the engine with the hydraulic pump and ignition distributer. Then, there would be the matter of the governor. I may get some time to think and design and maybe tack together something this weekend as I have Thurs/Fri off. I've got a 301 NA diesel exhaust manifold and want to see what it would take to get it on the side of the gas cylinder head, but I have doubts that would be possible with the intake manifold right next to it. I'll try and take some pics as i go along. |
Posted By: AC7060IL
Date Posted: 31 Dec 2025 at 8:56am
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Downdraft carb attached to topside of D2900 intake that would accept a turbo top hat? Fabrication to intake will probably necessitate carb mounting anyway? Why not fab it for a 650 2bbl Holley downdraft? Or any auto carb that allows easy access & assortment of fuel jet sizing for both farming or pulling setups? |
Posted By: AC7060IL
Date Posted: 31 Dec 2025 at 9:09am
| If D2900 cylinder head could convert onto G2800 with larger carb fuel jets, turbo boost, etc,,, THEN custom 2 piece tuned scavenging exhaust headers would be the balls to give that cross-flow D2900 cylinder head it’s appreciated breathing power!! |
Posted By: injpumpEd
Date Posted: 31 Dec 2025 at 10:52am
|
Pullers convert diesel heads to spark plugs for methanol, or even gasoline pulling engines. The diesel conversion helps with higher compression ratio too. The conversion would be an ideal application for Dave Kepners DJ Update EFI system he makes for JD gas tractors. Dave lives here in Walnut, though I am not involved in his systems, and he doesn't want to branch to other brands, but Dr could lmao! ------------- 210 "too hot to farm" puller, part of the "insane pumpkin posse". Owner of Guenther Heritage Diesel, specializing in fuel injection systems on heritage era tractors. stock rebuilds to all out pullers! |
Posted By: coggonobrien
Date Posted: 01 Jan 2026 at 3:40pm
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Posted By: DrAllis
Date Posted: 01 Jan 2026 at 3:41pm
| We have had a marvelous start to 2026 !!! Who would have thought a diesel exhaust manifold from a 180-185-190 or Gleaner "F" would bolt right on a G-2500 or G-2800 cylinder head ?? Well, it certainly does and with about 2 minutes worth of grinding on each end mounting holes. With every discovery like this, there is usually a downside. The one thing I will have to fabricate is the up-pipe from the diesel manifold to the muffler. The diesel pipe is 2 inches closer to the valve cover so the muffler either needs a new hole in the hood or an up-pipe with a jog in it. A very minor detail compared to fabbing up a whole complete exhaust manifold !!! There are tons of these diesel manifolds in salvage yards to be had. I may have to fab up some sort of heat shield to warm up the intake manifold in the center. Probably not needed in summer temps but winter temps I can see why it might be needed. It will be bolt on and could be removed if desired. |
Posted By: SteveM C/IL
Date Posted: 01 Jan 2026 at 11:29pm
| Well HAPPY NEW YEARS Doc!!! |
Posted By: coggonobrien
Date Posted: 02 Jan 2026 at 4:32pm
 
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Posted By: tbran
Date Posted: 02 Jan 2026 at 4:52pm
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FOR FARM USE- suggest a 1" channel laid on top of the intake - weld up the ends - and put a fitting in the exhaust probe hole and direct it down to the box via fitting. Probably gonna need some heat in the intake for efficiency and eliminate lean condition or allow a leaner mixture for general use. (not that a gas XT would burn a lot of fuel anyway :-) ) I had mocked up a turbo manifold on a XT and mentioned it on here when I think it was Doc that said, and what are you going to do with it at 8 gallon per hour and gas was $4 at the time... I put back stock and sold the XT gas , I wasn't thinking - just playing. ------------- When told "it's not the money,it's the principle", remember, it's always the money.. |
Posted By: DrAllis
Date Posted: 02 Jan 2026 at 6:18pm
| My plan is to build a simple steel box around that area that needs heat, secure it to the outside two existing intake manifold bolts and then going up as high as the pyrometer probe hole and then up to the muffler u-bolt clamp. This will help support the weight of the muffler and keep it from turning. But for now, the main goal of a solid not-cackling exhaust manifold has been achieved !! Interesting how the 180 intake manifold throat looks like it has a NASCAR restrictor plate (4022853) slug pressed inside it. The restrictor slug measures only 1.125" I.D. and the throttle plate bore on the Zenith carb measures 1.250". This small throat isn't on the One-Ninety or XT gas tractors. So, besides slowing down rated speed to 2,000 RPM and a smaller carb, the restricted throat choked the HP down to 65 at the PTO. |
Posted By: AllisFreak MN
Date Posted: 02 Jan 2026 at 6:23pm
|
Now we need to hear how it sounds . ------------- '49 A-C WD, '51 A-C WD, '63 A-C D17 Series III, 1968 A-C One-Seventy, '82 A-C 6060, '75 A-C 7040, A-C #3 sickle mower, 2 A-C 701 wagons, '78 Gleaner M2 |
Posted By: AC7060IL
Date Posted: 02 Jan 2026 at 7:40pm
| DrAllis, that exhaust manifold looks excellent! Wonderful job! Maybe don’t lock-down/completely tighten your planned fab’d intake heat box to exhaust manifold &/or /muffler clamp? Let intake do most of supporting muffler? Do Attach it loosely to exhaust manifold but allow for it’s necessary freedom of movement for its heat cycles? |
Posted By: DrAllis
Date Posted: 03 Jan 2026 at 7:32am
| When I get around to the intake manifold heating area, I will take some pics and post them. I'm still laughing about how the non-turbo diesel exhaust manifold bolts right on and fits !! |
Posted By: coggonobrien
Date Posted: 12 Jan 2026 at 8:57am
  
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Posted By: DrAllis
Date Posted: 12 Jan 2026 at 9:28am
| I built a hollow steel box around the warming pad area of the intake manifold to build heat from the exhaust components in that area. Included is a vertical support plate for the mufflers U-bolt clamp to connect to and help stabilize the muffler. If the heat build up isn't adequate (excessive frost at the intake manifold), I can direct a small amount of exhaust down from the 1/4 pipe thread pyrometer hole in the exhaust manifold. Once the hood is in place a good deal of this is covered up. I may just leave this tractor as a gasser now and focus on building a narrow front end for tractor rides. |