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 Post subject: LeRoi engine specs
PostPosted: Thu May 05, 2016 10:48 pm 

Joined: Wed Aug 25, 2004 3:03 pm
Posts: 138
Location: Wichita, Kansas
We have a 2000 cu in LeRoi V-8 in a Plymouth locomotive and are doing a valve job on the heads of this engine. We can not find any information in all of the manuals that came with the engine regarding torque specs for the head bolts. Does any one have any information regarding these engines. I might add that this type of engine was used for pumping and running cotten gins. They were also configured as a 4 cyl. Any help with this information would help us finish this project.


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 Post subject: Re: LeRoi engine specs
PostPosted: Fri May 06, 2016 4:24 pm 

Joined: Sat Oct 17, 2015 5:55 pm
Posts: 329
Stewartstown Railroad has one of the few Plymouths still with a Leroi engine, you might ask them. The person who started this thread:

viewtopic.php?f=1&t=39367

is one of their guys.


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 Post subject: Re: LeRoi engine specs
PostPosted: Fri May 06, 2016 6:58 pm 

Joined: Wed Jan 15, 2014 9:14 am
Posts: 174
Try to find the specs if you can. But if nothing can be found, here is what I do on some of the weird engines that I work on.

Measure the diameter, thread pitch, and length if it's a bolt. If it is a stud, length will not matter much. Next, start looking at similar vintage engines that you can find specs on (ie. Continental, Fairbanks morse, Allis Chalmers, etc.) And try to find one that uses same size bolts, close to the same length if possible. If you can find a few examples, take the average torque spec and use that. It is not ideal, but I have done this 4 or 5 times and never had a failure.


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 Post subject: Re: LeRoi engine specs
PostPosted: Fri May 06, 2016 8:08 pm 

Joined: Fri Aug 20, 2010 8:25 pm
Posts: 246
Well... you can always torque them until they snap and then back them off a quarter turn....

I am kidding...

There are many variables; strength of the base materials (likely cast iron for that vintage), strength of the bolts (original or replacements), dry fasteners or oiled fasteners (it makes a difference), fine thread/coarse thread, class of thread (ie tolerance of the threaded surface), gasket material, flatness of mating surfaces, etc. etc....

I think finding a few similar vintage engines of the same size with similar bolts and averaging the torque specs (if you can find them) is probably a safe bet.

I (with a team of fine folks) rebuilt a 1919 4 cylinder Buda gasoline engine in a Plymouth Model BL2 locomotive. It is a real cast iron monster, ~ 75 hp out of ~ 1000 pounds of iron. We had an real copy of a Buda engine repair manual, but back then torque wrenches were not invented yet and there were no torque specs anywhere in the manual. Believe it or not, a whole manual about rebuilding the engine (including how to manually scrape the main crankshaft bearings for a proper fit) and not a single torque spec anywhere in the manual. The official repair manual did have a "tightening sequence diagram" which told you to start in the middle of the cylinder head and work your way outwards in a spiral pattern until you tightened all the cylinder head bolts. So they did understand the need to spread the stress of the engine block to cylinder head joint evenly around the total assembly, but they had no way to specify torque values.

A good mechanic was supposed to just "know" what the right torque was for any given fastener.

From Wikipedia;

"The beam type torque wrench was developed in the late 1920s/early 1930s by Walter Percy Chrysler for the Chrysler Corporation and a company known as Micromatic Hone. Paul Allen Sturtevant—a sales representative for the Cedar Rapids Engineering Company at that time—was licensed by Chrysler to manufacture his invention. Sturtevant patented the torque wrench in 1938 and became the first individual to sell torque wrenches."

So engines from pre-1940's vintage probably never had cylinder head bolt torque values specified....

On the rebuilt Buda engine I replaced the original studs with new ones (5/8", I think), got the mating surfaces nice and flat and then torqued it up to about 90 foot pounds and watched for leaks (oil in the water, or water in the oil, bad compression, etc.). Then I thermal cycled it a few times (run it, let it cool off, run it again, etc.).

The safest route is to have two good flat surfaces with no nicks/gouges/grooves and a good quality gasket. Then torque it evenly to a lower value, run it, see if it is sealed up good. If it's a little "leaky" take the torque up gradually in say 10 ft-lb increments until it appears "tight". Moving the torque up slowly in even increments should be safe and reduce the risk of damaging anything.

Over torquing is (in my opinion) a bigger risk because you can break something. Under torquing just means something leaks, and you can always go back and "tighten it up" until it stops leaking.

Studs, bolts, and nuts can be replaced. Even threaded holes in old castings can be "refurbished" with thread inserts, one brand of which is "Helicoil" (tm). But if you break a casting you are in a whole new world of hurt.

Good luck, Kevin.


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