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24GLX - repower notes

5295 Views 17 Replies 4 Participants Last post by  Richard-tx
Now that I have had the opportunity to spend some time on the Onan P224 powered 16G with the shop made exhaust, I figured now would be a good time to describe the experience of the engine swap and the results.

1 - It does not sound like a 24G. It sounds very similar to my 818T. Maybe a little more rumble but not much.

2 - The tractor doesn't feel all that different. The Onan is a little heavier but not a lot.

3 - The engine isn't that much bigger and yet it is. Compared to the M18 that came off, it looks to be at least 30% larger. In terms of displacement, it is 50% larger. (42 cid vs 60 cid) It is slightly larger than the B48 but not by much. The 3 qt pan does reduce the engine ground clearance compared to the M18 but the transmission is still lower than the engine. The rear cultivator will still work.

4 - As near as I can tell the rear engine adapter from any B series Onan will work with the P224. Not sure about the CCKA.

5 - I had to drill and tap two 3/8-NC bolt holes in the P224 block. There was a casting depression in the crankcase where the holes should have been so locating the position for drilling and tapping was easy.

6 - The crankshaft on this engine had a long 1/4" slot in it. That meant that the shaft seal in the adapter plate was pointless. To seal the transmission I put some RTV around the OD of the bearing plate. That has worked well so far.

7 - The crankshaft was short by about 3/4 of an inch so I made an extension from an old K301 crankshaft and held it on with a SHCS. A metal lathe made that an easy task.

8 - I tied the oil pressure switch through the ignition. To keep the cranking time low, I added a relay so that when the starter was engaged, the coil received power. Without the added start relay it would take a second or so to build pressure before it would start.

9 - A new throttle cable is required. The throttle cable for the M18 is too short. The original choke cable however is just fine.

10 - Rewiring the ignition relay was easy. I just followed the schematic for the 24G.

11 - I added a 4 wire connector at the engine. I decided to use the same connector used on the 24G. It seemed to make sense should I ever want to remove the engine.

I ran it through some wet grass and leaves. Not once did I feel that the engine was approaching maximum load. I was running my modified 50" deck with the 40" deck pulleys. Just to spin that deck with Gravely blades requires 12 hp. I have spun that deck on a 5665 with a freshly rebuilt engine governed at 3300 RPM, the throttle plate was almost wide open. Held wide open the engine would run up to about 3400 RPM. Dropping the PTO clutch at an idle just spins up the deck. No worries about stalling the engine.

I redid the exhaust system to use 1-3/8" pipe. That actually worked out better than the 1-1/4" pipe. The 1-1/4" exhaust system will be used on my 818T or CCKA when the time comes. I will be ordering muffler guards next week.

This tractor now is on the same class as the Pro16. I have to start it just to listen to it run.

All in all, it was a pretty easy job, exhaust system included. I just took my time and enjoyed the process. My recommendation is that if the opportunity arises, do the upgrade to a P224. It is worth it. It is as significant an upgrade as going from a K301 to a M18.

Two word summary? "Quiet Giant" comes to mind. One word summary? "Sleeper"

I did receive some assistance and parts from a few members here. I do have to thanks them for their help.

Don in Fla. who supplied the chunk of crankshaft
Tom, aka Popcorn, who sold me the adapter plate
Boomer - the used Onan parts guy who supplied the correct throttle pieces and engine guard that the PO lost.
Onanparts - for the exhaust gaskets, etc.

Pictures to come.
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Thank you for taking the time to share the more technical aspects of this with us. While not a difficult conversion, not something I would likley jump into since I don't have some of the resources you do.

Should my 16G, (18GLX ?) ever need an engine, I will likely go the new engine route. But actually I won't be unhappy if I never need to.

Reading this last night got me thinking more about the debated differences between the M18 supplied on my tractor, marked 16hp, and other M18's, GRAVELY or other wise.

I have a Kohler master parts list for the M18, M20 engines, and after even more review of the parts used on verious spec numbers, there is no doubt in my mind that the M18 on my 16G is every bit the same engine power wise as the same year 18G engine, and many other M18's installed on various other brands and years of tractors, GRAVELY and otherwise, and advertized as 18hp.

In fact, there is nothing in those parts breakdowns to imply that any M18 produced measurably more or less power than any other M18.

And just to be clear, for those who will say that the carb is different - carburators cannot dictate horsepower, they can only limit max rpm by limiting max air flow - not a factor on a governed engine. The throttle bore of all the M18 and M20 carbs are the same - so their cfm is the same.

Cam lift and timing, ignition timing, valve size and compression ratio are what control the production of hp and torque in an engine - all of these elements appear to be the same on all M18 engines.

And now with my governor set at 3550 rpm, I am very happy with my 18 hp.

Again, Richard, great conversion and I'm sure it will serve you well, especially as you know how to treat the PTO clutch with respect.

Those Onan engiens are great - shame they are no longer made.

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Richard, Excelent summation of the issue.

Call me a wild man, but I usually plow snow at full throttle in 4th gear!

Unless it's really deep, then I move it down to 3rd gear.

Because of rebuilding costs, and because I have little faith in "used" stuff, if I needed to repower the 16G tomorrow, I would likely go for a new Kohler Command PRO EFI, 23 or 25 hp.

It will bolt on, my bagger vac will work, the intake and exhaust might require some mods - that I can handle.

While it is not and ONAN, I not sure anything out there is. May people rave about HONDA, but I have had bad experiances with HONDA small engines.

The other choice is Briggs, who I have had good luck with on other equipment, but somehow the Kohler looks like the better choice of the new offerings.

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I am plowing asphalt paving, and the snow is often wet and heavy. Out typical snowfall is 6".

In 4th gear the snow rolls nicely off the blade, at slower speeds not so much. I know this is an issue you have commented about regarding the rider blade design.

With a 6" snowfall I can drive right down the middle with the blade straight, then a make a pass or two on each side angled, and I am usually looking a black paving 12' wide, with maybe just a little touch up her and there - and that was before all the improvements. So As fast I can drive around the circle (the drive loops around the house) three to five times in high gear, a 6" snow is largely cleared.

Then I have claer the 40' x 40' pad, a little more detailed, and a fair about of backing up, but not more than 15 minutes for a 6" snow - when it's more than that, it starts to become "work".

I had my 300 ft drive plus my father's 270 ft drive to do. It would take a while.
I would imagine gravel is a much tougher situation? I have never done that. My "loop" is about 400', plus the pad, just a little under 7,000 sq ft. One of those big snows last year had me out there nearly 8 hours.

I just came in from test fitting the cross shaft - fits perfect!

Pictures on the thread tonight if I get time.

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