JD 318 engine

dzc3

Member
I just "inherited" an Onan engine it is disassembled. I have no clue how to go about reassembling it. Is there a PDF I can down load or a book on these engines? Any information will be helpful Thanks in advance
 
I dont have a direct answer for your question but I will say that I have a 318 and when the Onan became tired I quickly realized that Onans are not cheaply serviced. Retro-fit replacement engines are far cheaper than the Onan and are much better units. The modern commercial engines have a longer life expectancy and use far less fuel than the Onan. I settled on a Vanguard for my 318 and couldn't be happier. It is quieter, vibrates less, makes far more power and uses much less fuel than the Onan. The crankshaft pulley and clutch that came on the Vanguard is slightly larger than the Onan which sped up my deck to where I always thought it should be. My 318 will flat cut grass now. It'll burn the belt off the deck before it slugs the engine.

The replacement engines come with a warranty. The Onan that cost more to rebuild than the Vanguard cost new has no warranty.
 
Where did you get the vanguard engine? Did you have to purchase an additional kit or did it "bolt right up" ?
 
I have the 318 with the Onan still on it and I like it. Yes, Onan parts are spendy. So are replacement engine kits.

There is a discussion on Weekend Freedom machines website that tells how one guy put a replacement engine on his. It involves changes to the drive shaft, special engine mounts, and changes to the electrical system as the electrical on most modern large engines is more involved than what the Onan required.

I guess its your call what you do but would depend somewhat on why your engine has been taken apart. (Check the valve seats. Nobody ever adjusted the valves because it was so involved to do it and they tend to beat the valve seats loose at about 1000 hours if it was never done.)
 
My engine came as a kit ready to bolt in. They only thing I had to modify was the throttle and choke cable. I used the original cables for both but they had to be shortened. I also had to purchase a different belt for the mower drive. I cant remember if it was longer or shorter. The engine install was easy. I did it one night after work and had it ready to mow that night all except for the mower belt. My mower still looks original from the outside. You'd never know the difference unless you heard it start up or looked under the hood. The V twin Vanguard sounds very different from the opposed twin Onan.
 
Parts and service manuals here:
http://casecoltingersoll.com/showthread.php/18752-Engine-Section
Parts available here:
http://boomersonanparts.com/
Examine and measure your rods,crank, pistons and bore before deciding what to do. IMO, the Onan is as good as or better than anything else available. Except for fuel consumption, they are thirsty. But consider this: Every premium garden tractor of that era used them, Case, JD, Cub Cadet. There must be a reason! If you can avoid machine work, other than valve grinding, they are not much more expensive to repair than any other, using original equipment parts. Rings, gaskets and a valve job will fix most. You can source used parts if needed to keep the cost down if pistons, rods or crank is needed. Either the link above or I can help with that. If you can do your own work it should be a LOT cheaper than a Vanguard repower. And faster.
 

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