Max bore on 730 block

[schmitty]

How big of a sleeve can be put in a 730 block? Machining will definitely be required. I can get 5.5" Cummins sleeves, and pistons are no problem. This is for a 400 pulling tractor.

 

[jon f mn]

I put 4 5/8 from a 504 in a 930 and that
was about the max because I had to remove
part of the eater pump housing to get the
front sleeve in. You could get some more by
boring the sleeves.

 

[EP]

4 7/8 is easy with a thin custom sleeve​, and you can still have a decent counterbore. Anything over that you will most likely have to fill in the water ports in the head as the bore will be getting into them. Guys are going out to 5.125, 5.250, then you will be moving centerline's and compromising the integrity of the top of the block more, but it can be done. It all depends on how much money you want to spend and the level of competition you are up against.

 

[big tee]

We went 4 and 15/16.---Tee

 

[brutus49DC]

My puller is 5.125 bore (7.5 stroke)with ductile cast sleeves from Power Bore. There are a few at 5 1/4 but things start getting a little thin. Forget about using Cummins ect. parts. Custom sleeves and pistons are pretty much required for anything over 5"bore. Lycoming 5.125 pistons will work at 7 inch stroke or less. IH 400 small pin rods will work up to 6.5 stroke or a little more. After that billet rods are required to clear the block with out too much clearance work.

 

[brutus49DC]

Bore center to center distance does not change as there is no room to move them. At 5.125 you can have a nice top flange.

 

[EP]

Did you go 5.125 using the 30 series block or were you lucky enough to come up with a 70 series block. I have looked for several years for one of those with no luck. I left my bores a little smaller and turn it close to 3000 RPM if I need to.

 

[brutus49DC]

I bought an 870 gas engine with a spun rod brg. from a salvage yard for $750. They didn't realize what they were selling and I didn't bother to inform them! The 30 series block will go to the same bore but the 70 series block is thicker on the bottom and has bigger head bolts.