Can I put 730 LP pistons in a 630 engine?

[Paulcat9]

Hi, I am restoring a John Deere 630 for tractor pulling. I want to put 730 LP pistons in my 630. My thoughts are to cut the counter bores out and use a 730 repair sleeve. I know I will have to use 730 connecting rods because of the wrist pin size difference...but are the crankshaft rod journals the same? Or do I need to change the crankshaft too? I also need a good carburetor because this tractor was a barn find and the carb is missing some parts. Any help and advice would be extremely appreciated!

 

[HFP]

A 630 isn't a very common tractor for pulling due to the weight, but I'm sure you are aware of that. If you are going to spend the money to bore and sleeve it, I'd find a piston with more bore and compression than a 730. If you aren't going to stroke it, you will probably need to lengthen the rods to get much compression out of it. So worst case you could use 1/2 of each type of rod when you do that. If you don't get much for responses here, try posting this question down on the Tractor Pulling or John Deere parts of the forum.

 

[matthies]

Just pulled a 630 crankshaft last night, due to a spun main bearing. The way it looked last night, it can't be stroked much, as when I pushed the piston/rod into the bore farther, it didn't go far. But never had anything stroked so maybe you don't need much.

 

[Paulcat9]

Just pulled a 630 crankshaft last night, due to a spun main bearing. The way it looked last night, it can't be stroked much, as when I pushed the piston/rod into the bore farther, it didn't go far. But never had anything stroked so maybe you don't need much.

Any idea if the rod journal is the same size for both engines? I know the stroke is the same, but wondering if I can just use 730 connecting rods... I can't seem to find that information on the internet.

 

[used red MN]

Any idea if the rod journal is the same size for both engines? I know the stroke is the same, but wondering if I can just use 730 connecting rods... I can't seem to find that information on the internet.

Hello Paul, welcome to YT! Looks like 3 3/8” for the 630 and 3 3/4 for the 730. That is from a Diesel truck repair manual from the early 70’s.