New Life for an Old Allis|
by Tyler Woods
My friend Jon, has an old '39 Allis Chalmers B. He thought it a marginal tractor that had long since served its time. She smoked terribly and never had much power but he couldn't afford another so he was limping along with what he had. Jon's Allis has a small front loader and though it doesn't carry much, it serves his needs. It was the hard starting and low power that made him think it was time to replace the old girl.
Jon called me to help him discover why his tractor wouldn't start and I found his compression ranged from 50# to 65# max. Even with new plugs it took about 20 minutes to get her to catch. Once fired up, it was obvious you should never start this tractor in a shed with animals present. Jon couldn't hide with that tractor running. This is no joke, Jon used his tractor to do some backyard landscape work at a rental house he owns. Once he got the Allis started, a neighbor came over to see if he needed the fire department. By all the smoke his tractor was putting out, the neighbor seriously thought the building was on fire.
Jon wasn't ready to junk his tractor so we priced a full rebuild. Parts, paint and decals came to about $600. We added $200 for those extras you can't know, but can count on, and Jon figured $800 was within budget. It would at least increase the trade value when he could get a bigger tractor.
Jon had never been inside an engine before and didn't want to try this alone. He could do all the cleaning and painting but he wanted me to help with the engine work. On the first Saturday, we got the tractor split, head removed and the engine on a stand. Jon had already removed the sheet metal and radiator so my job was easy. Things weren't nearly as bad as we had imagined. Someone had been in that engine recently (as tractors go) and the sleeves were like new, the pistons were like new and the mains and rod bearings were fine. I measured the ring gap and found the problem. Ring gap is the distance between the ends of the rings as they sit in the cylinder sleeve. They need at least .007 and should be no more than .017. These rings had at least .030. No wonder we had no compression.
I figure the earlier mechanic failed to measure the ring gap when he did the previous rebuild. We ordered new rings and waited for our next work day.
The second Saturday, I honed the cylinders, installed new rings and the cleaned pistons. I had taken the head to a favorite shop of mine and it was ready with valves freshly ground and face milled. The valves, guides and seats were in great shape and it pressure tested fine. I thought $35 was money well spent for all that work. Jon had sent the pistons to the shop for cleaning. I never do that preferring to do that work myself. The shop had never seen pistons like these and didn't know to remove and save the shims. All the shims went to the bottom of the parts washer and had to be replaced. I spent the whole Saturday matching pistons to their spot on the crank and making shims to get the correct bearing adjustment. Another little feature of the parts washer is that it removed the piston numbering we had done. I hadn't planned on them going through a parts washer so the numbering was done with a felt tip marker.
Saturday number three found us remounting the engine and installing the head. Jon had done a great job of cleaning and priming everything he could reach and the cosmetic work was starting to look really good. We couldn't install the rocker assembly because the shop had removed the studs in order to mill the face of the head. By oversight, they didn't include them when the head was returned and I didn't think to ask for them when I picked it up. The biggest problem was time, not the cost of new studs.
Last Saturday was our fourth available day with the Allis. Jon had begun painting all the less accessible parts with new orange paint and it sure looked good. We got the new studs installed and mounted the rocker assembly, rebuilt carb, magneto, radiator and remaining running gear. The front wheels mount so easy on an Allis that they hardly get mentioned. With everything ready to go, we attached the chain to the truck and pulled the Allis for her first attempted start. Ooops! Gas was dripping from a stuck float in the carburetor and we had no fire out of the magneto. The float was a simple adjustment but I had never been inside of a magneto before. There is a first time for everything and this was mine for magnetos.
Fairbanks-Morse Magnetos are really simple inside and this problem was easy to isolate. The coil is held in place by two mounting screws that clamp down the coil and give it a ground connection. The screws were loose by about 1/8. After tightening the coil and reassembly, the magneto fired perfectly. All back together, the Allis started in about 20' of pulling. Jon was excited, he never thought it would go this easily. I have to admit, I'm always amazed when a new engine starts. I don't know why. You do good work, pay attention to detail, follow the rules and engines should start. It sounds good but for some reason I must not believe it because the amazement of that first fire is always present with me.
Once the engine warmed up, I adjusted the valve lash and buttoned up the valve cover. Jon has more painting to do and sheet metal to install but he's really happy with the old girl now. The little Allis has good horsepower, starts easily and runs well with NO smoke. I expect some initial smoke from engines I rebuild because I use a fair amount of Lubriplate to hold things until the oil pump can come up to pressure. This engine never smoked. I'll run a compression test after a month or so, to let the rings seat and get a stable reading, but I think it will meet spec just fine. Jon tallied up the cost and we came out at about $400. Half what we thought it might cost.
As I loaded up my tools, we talked about how soon he would be complete with the painting and new decals and which parade he could enter. I want a picture of Jon proudly driving that Allis B down Main Street. He'll be easy to spot. Jon will be the guy with the big smile.
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