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Case 646 Repower

10K views 20 replies 6 participants last post by  Case-Closed 
#1 · (Edited by Moderator)
After being followed home by a ratty old 646 in August I am about ready to begin it's reassembly. I have been trying to remember to take pics as I go so here they are. The previous repower was a 16 Hp Briggs with a vertical shaft and all I can say is it was a bad choice. With no space under the hood the battery was left sliding around on the floor board. This engine also had a dead clyinder so it really did have to go. The new engine is a Kohler CH 18 that I got for a good buy. Everything has been fit and refit and I think the final assembly is at hand.

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#3 ·
Well I made a little progress today on the 646 and the puzzle is starting to take shape. The first pic is of the motor mount and oil cooler installed. The engine sits with the pump forward just I have seen done by many others with the oil cooler mounted near the back of the engine compartment. It's a tough deal to make everything fit but it can be done. For vibration reduction the engine sits on a quarter inch thick rubber pad. Tomorrow I hope to mount my new oil lines and a new filter on the return side.

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#4 ·
I know a guy that has nice reproduction dash tower panels for sale if your missing yours.

That repower looks great! WAAAAAY better than that Briggs.

Nice job!
 
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#5 ·
I managed to get in a nearly solid undisturbed day working on the 646 repower. I got the muffler and supports put together, I used an ATV muffler rated for 600cc because I want this tractor to be a whole lot quiter than my 444. The hydraulics have also been fitted and I need to do their final installation in the next few days. I hope to get some paint on newly welded parts before the real cold weather gets here and then do a final assembly of this jigsaw puzzle.

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#9 ·
It runs!!! But!! I seem to have a hydraulic issue and I think it might just be the pump. It came with a Rexroth S16S5AH26R and I find no reference to that anywhere in the case world. I have learned that this pump is 2.9 GPM and that sounds a bit low to me. Does anyone out there know what pump should be in this tractor? I have heard that a 6296k63 from McMaster Carr is a direct replacement and puts out 4.52 GPM at 1000 PSI. I would really like to know if this is correct before I drop $200.00 on a pump.
 
#11 ·
I managed to find a replacement pump and it is made by Eaton. I will be usinfg a 26004RZC rated at 10.3 GPM at 3000 RPM and 5.5 at 1800 RPM. The size and ports are Identical to the one I have and it's even made in USA. You can see in the pics how the pump mounts up and it took a mere 15 minutes to pull it.

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#12 · (Edited by Moderator)
I recieved the new pump yesterday and installed it this morning. Everything was identical to the the old Rexroth so it bolted right up without a hitch. The difference in performance is astounding. I thought I might see a bit of difference with the new pump but instead it's huge. The weather here calls for highs in the low teens so rigerous testing will have to wait, as I don't like to freeze if I don't have too. I hope to wrap up this whole engine swap stuff and move on to adapting my sleeve hitch tiller to go on the 3-point on the 646. I suspect one of the triangle shaped adaptors I see all over the internet will easily adapt to suit my needs.

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#16 ·
The old cooler was still in place but damaged and leaking and of course no fan. I tried to follow the "70" series of tractors that followed the 646 with cooler location, and I hope it works ok. I would like to know what the temp of the hydraulic system should be during operation. I am not certain that the air flow across my oil cooler will be adequate or will I need to install a fan.
 
#18 ·
I would highly recommend a fan. A fan that pulls the air through rather than blows air through it is best for heat exchangers. This is how all cars are equipped with a shroud. but anything is better than nothing.
 
#19 ·
I'm set up so the Kohler pulls air through the oil cooler but I have a fan that could easily be added if need be. I did discover though that cold weather starting is going to be a problem. I tried to start the tractor this morning at 17 degrees and it would not go. I suspect a brand new engine coupled to a brand new pump might have something to do with it. I intend to put a stick on oil heater on the hydraulic tank to see if that solves the problem unless someone has a better idea that has worked for them.
 
#20 ·
You should be in good shape then for cooling.

I have heard guys covering the tractor and placing a heat lamp or 100 watt light bulb under the tractor to keep it warm. This needs to be maintained when not in use though.

Also make sure you have a lighter grade oil in everything including the engine. A synthetic oil flows much better in cold weather. I've started my old Onan's in much colder weather than 17* before so that should not be an issue. I had Amsoil Synthetic 10w30 in the engine and Amsoil15w40 in the hydriv.

It could be that its taking awhile to get gas, sometimes priming the carb with a shot of fuel before starting gets thing fired up quicker.

I hope it all works out for you. :thumbs:
 
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#21 · (Edited by Moderator)
A good friend of mine runs several diesel vehicles and he uses a Katz stick on heater on each and all of them. The surface must be squeaky clean for them to stick but he swears by them. I think I might try the magnetic heaters first since I just happen to have a 500 watt unit in house. It would make sense that once the new engine and pump have a chance to wear in a bit the starting problem will fix itself.
 
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