Lead additive in 1940s AC tractor ?

94ranger55 said:

I am getting a 1940s AC tractor this weekend !! My question is, should a lead additive be used in the gas ???I figured since its from the 40s the engine was designed to run on leaded gas .What do you guys think ??? Thanks !

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Not needed unless this a work tractor that's going to run 8 hours a day, 5-6 days a week. Even then, in the long run it would be more cost-effective to run it until the valves get too deep and leak. Then pull it apart and do a valve job with new hardened seat inserts. Overall that will be cheaper then buying any additive (which won't have lead in it).

The only issue with non-leaded gas in older engines is valve-seat recession during high RPMs, high heat, hard use and long hours. Not usually an issue with a part-time use collector's type of machine.

I'd be more concerned about what motor oil you use. Most motor oils sold since 2009 or highway use lack the ZDDP lube-additives needed for flat-tappet camshafts - like your AC has - along with just about all other cars and tractors made mid-1980s and back.

I have a tractor and sold an old international crawler that I had run the snot out of. These machines are owned and run by special people. They have their own forums, especially for something from the 1940s. I would seek that forum out.

Modern EP grease is fine for chassis grease.

Highbeam said:

I have a tractor and sold an old international crawler that I had run the snot out of. These machines are owned and run by special people. They have their own forums, especially for something from the 1940s. I would seek that forum out.

Modern EP grease is fine for chassis grease.

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+1 Seek out the experts. I've heard you can really get into trouble running detergent oil in an engine that's only ever seen non-detergent oil.

If its ever had a valve job chances are that hardened seats were installed and lead is not needed. As was said earlier, its probably cheaper not to use the lead additive regardless.

I suspect just about any modern oil is much better that what was available in the 40s but again, the experts would know.

94ranger55 said:

The tractor has been sitting for some time but she fires right up !Any recommendation for what motor oil to use ? I am a little rusty on my antique oil types...if i remember correctly non detergent is used for the older rigs ????Also what other things should I change ,check or add ie tranny fluid .Also i assume a regular grease that you would use on a modern day industrial tractor would be sufficient?

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A 1940s AC tractor engine isn't much different then one built in the 1970s. Very little difference in technology.

The isssue of non-degergent oil versus degergent oil is this. If a tractor is old and wasn't maintained very well - it could have inches of sludge built up inside the engine. Especially in the oil pan and valve-cover (if an overhead-valve engine).

If you dump in high degergent oil into an engine that is that dirty inside, stuff starts coming loose. If that happens rapidly, it could damage the engine -but that's kind of rare.

If you have no past history of maintenance - and have no idea of the internal status of the engine - there are two simple approaches. 1st. Just use non-degergent oil and play it safe. 2nd. Put in a detergent oil and watch the dipstick closely for oil color. If it turns black real fast, you might want to put in non-degergent oil instead.

Note that even old tractors run for 50-60 years with non-detergent oil - can be fairly clean inside. All depends on how they were run and what sort of maintenance they got.

Semipro said:

I suspect just about any modern oil is much better that what was available in the 40s but again, the experts would know.

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Just about all motor oils made since 2009 that are intended for cars and trucks driven on highways have LESS anti-wear additives, not more - then older oils.

Thus the benefit of buying off-road, racing, or tractor oil for older machines.

got an old MM im working on, Went to mobil oil web site and they recommend 20-50 racing oil.

EKLawton said:

got an old MM im working on, Went to mobil oil web site and they recommend 20-50 racing oil.

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Funny you mention a MM. The 2009 and newer highway oils cut back on the anti-wear ingredients that keep flat camshaft followers from wearing.

Out of the many brands of tractors I've worked on, built from the 1920s up to 1980s - the MMs are the only ones where I've found cam and lifter wear problems. If I had an MM engine with those wierd long rocker-type lifters that you access from the side - I would definately want off-road or racing oil with lots of ZDDP.

That's assuming your MM has a MM engine. A few have Hercules.