G900 bored to 504

Anonymous-0

Well-known Member
I have a 1968 G900 diesel that I bought for a bargain price. After running it some, I heard a slight miss and and occasional knock. I tore it down and it turned out to be a broken piston land and ring. It scored the block. I overhauled it by having the blocks bored out to G1000 standard size (504), with new pistons, valve job, etc. It now starts really great and sounds sweet. I understand this combination raises the compression ratio to around 17-1. I used it on a 15 foot brushhog, which it handled just fine, but I"m looking to replace the mower with a 20 footer. Would this be too much for a 504 inch G900? The G1000 is 110 HP, and this tractor is now a couple of points higher compression than a stock G1000, so would the power also be over 110HP? The governor was set up when I got it and it holds 2000 RPM under load.
 
I would tend to think that it would handle it without any issue.

On your 451 to 504 rebuild, my 900 with a 451 also broke a ring and scored the wall pretty good, so this summer it's going to get a 504 rebuild. What else did you do to it? Did you have the pump worked on? If so what specs did you have it adjusted to? I'm going to be boring mine to 504 std.
 
I asked Ed Welters about the pump and he said it would be fine as is. I never thought at the time to ask him whether the power would increase due to the larger displacement, with the same pump setting, or whether it would be limited to whatever the current pump setting is. After thinking about it, I suspect the latter will be true. I used Welters as a parts source and machine shop. They went through the heads and valves and bored the G900 blocks to G1000 standard size. I put in all new pistons, etc.

My pump, or at least the governed speed, was already turned up by the previous owner to 2000 RPM. The tractor will pull a load at 2000 RPM. I don't know the specs the pump is set to and I just left it as found.

It feels stronger than before, but the biggest difference I see is how easily and quickly it starts now. The 17-1 compression really made a difference. I don't know if the power also increased. My "seat of the pants" impression is that it did. I do not know whether it will also run hotter under a heavy load, which is why I was questioning the wisdom of getting a 20 foot brush hog.


Ronnie
 

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