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Discussion Starter · #1 ·
I have an 812 which I waffle back and forth on, either it's a parts machine, or it needs an engine and some cleanup.

I've been considering using something like http://tewarehouse.com/GX660-TXA2

From what I've read, that has the right crankshaft. Is there an adapter plate for it to bolt up to an 800 tranny? If I decide to embark on this project, what else should I be taking into account?

TIA...
 

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The exhaust is another expense. If you don't care if it looks like crap and sounds the same, then it will be cheap. If you want it to sound and look good, then it will cost.

You will have to find someone who is willing to make an adapter or modify an existing one.

Other than that, the rest is easy.

Personally I would go with the highest horsepower, most expensive engine I could afford.
 

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smallenginewarehouse.com has in the past sold Honda engines in kits that included an adapter plate. I believe Bruce G makes them as well. That looks like a nice motor, I have a soft spot for the Vanguard and if I had a lot of disposable income I'd put one on both my riders.
 

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Discussion Starter · #4 ·
Yeah, I know I'll need an exhaust system. These outfits (tewarehouse, smallenginewarehouse) all seem to sell them; I haven't looked into clearances or dimensions or anything, but I'm sure that's doable.

Thanks for the hint about smallenginewarehouse selling a plate, I'll look for that. And presumably Bruce will be along.
 

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Another thing may be the electrics. The 812 presumably had a coil and I think the new engine is a magneto so the ignition switch and wiring will have to be redone. Not sure about the charging system. The new engine may have it's own regulator which means more wiring changes. Since the 812 is pretty old, it is probably a good idea just to rewire the tractor. I would also put new fuel lines in and flush the tank.

I really think it is time to give the whole tractor an overhaul.
 

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One other thing came to mind. Use the same engine gear that was driving the transmission. Changing the gear can cause all manner of noise.
 

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I have an 812 which I waffle back and forth on, either it's a parts machine, or it needs an engine and some cleanup.

I've been considering using something like http://tewarehouse.com/GX660-TXA2

From what I've read, that has the right crankshaft. Is there an adapter plate for it to bolt up to an 800 tranny? If I decide to embark on this project, what else should I be taking into account?

TIA...
That linked engine will not work. You need an engine with a 1.125" X4" or 1.125"X 3 25/32" because of the need for the adapter plate nose. Add about $250 to the engine cost for a steel adapter to be made. You can also modify a plate off of a Kohler 12 HP to work on most engines. That is what I did for a Kohler Command Pro 18 HP.
 

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Discussion Starter · #9 ·
Oh wierd, I must have somehow ended up with the wrong engine. There's a version of that GX660 with a longer crank, but I can't find it now. Gotta be careful out there!

What I remember reading in other repower posts was that I need a minimum of 3.75" length. Is that right, or should I really be targetting 4 inches?

Good to know about the plate. I have a leftover K301 plate around somewhere. Don, do you remember what the mod is? Are the bolt patterns on the engine case compatible, and I just need to trim around the edges or something?
 

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Oh wierd, I must have somehow ended up with the wrong engine. There's a version of that GX660 with a longer crank, but I can't find it now. Gotta be careful out there!

What I remember reading in other repower posts was that I need a minimum of 3.75" length. Is that right, or should I really be targetting 4 inches?

Good to know about the plate. I have a leftover K301 plate around somewhere. Don, do you remember what the mod is? Are the bolt patterns on the engine case compatible, and I just need to trim around the edges or something?
Always go for the 4" model if available. Even it may come up 1/4" short but that is ok. The plate I used was machined flat in the recess toward the engine. Then a 16ga disk was made to fit in with a plug to fit in the shaft area that was drilled to clear the shaft itself. The plug and disk were siliconed to the adapter and the engine. The disk sealed up the hole in the adapter where the PTO shaft bearing sits too.That saves machining a seal area in the adapter for the crankshaft and installing a seal wear sleeve on the shaft. Bolt pattern was the same.
 

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Someone said "Most HP possible." Well that opens up all kinds of possibilities. There are LOTS of old car engines around that can be had for peanuts. That leaves you plenty of cash for adapters and plates and discs and things. And maybe an extra support wheel under the motor if you pick up a straight 6 or something else kind of longish.

Let's think BIG folks. I just saw a picture of a motorcycle with a 350 V8. 385 HP. Surely we can do better.

RL
 

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The problem with liquid cooled engines on a Gravely is the expense of having radiators made and having to relocate things like the gas tank, battery and more. Might be able to get enough cooling for a 1500 cc engine if the fuel tank were removed but even that is iffy.

Then you run into design limits. The internal PTO clutch has a limited amount of torque that it can handle.

Putting 100+ hp engine on a Gravely is a possibility just like the fellow that put a 400 hp engine on his Chevy Vega. He goosed the throttle once and instantly twisted the frame. He did it two more times before the frame broke.
 

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The plug and disk were siliconed to the adapter and the engine. The disk sealed up the hole in the adapter where the PTO shaft bearing sits too.That saves machining a seal area in the adapter for the crankshaft and installing a seal wear sleeve on the shaft. Bolt pattern was the same.
The is pretty much what I did when I installed the P224 engine on the 16G. THe engine I bought had a key slot instead of the woodruff key. That meant that the crankshaft seal was useless. I used RTV to seal the adapter plate to the engine.
 
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