730 D crankshaft

Anonymous-0

Well-known Member
I am working on my 730 engine - I lent my service manual to a friend and now it is lost. I would be grateful for the part number of the service manual so that I can order a new copy. In the meantime it would help if someone would confirm that the outside main clearance is 6 to 8 thou new and 15 thou maximum permissable wear.
 
I buy my manuals from Davenport Tractor. They have a web site. Their manuals are exact reprints of the originals. They recently advertised the paper quality has been improved since I bought mine, I feel sure you will be happy.
 
Not sure where you got that from, but 6-8 sounds excessive for maximum permissible, & 15 is just rediculous. Youll have lotsa oil leaking by, & hammering of parts. You need new bearings from Manitowoc Motor Machine in Wisconsin. Likely need to have the crankshaft turned, bearings sized to fit. Big job. Good luck.
 
I'd never put one of these two cylinders together without AT LEAST .004 clearance. I don't recall the exact numbers from the book but I'm positive they don't call out .002 (at least not for 80's, 820's, 830's, 840's) These things aren't Swiss watches and they need some extra room.

The allowance for out of round on the crank journals is .001. I'm almost certain the main bearing clearance "shoot for" numbers are .004 to .006 and I'll assure you that you are better off shooting for the high side.

If you crank is clean and round just measure it and have Manitowoc make you bearings with a hole about .005 + over your measurement. If the 730's have a center main (99% sure they do) better check it for ovality. Pull the center bearing halves out and torque the cap back on. Then measure at several places. Odds are pretty good you'll have some ovality. You need to take this into consideration when sizing the center mains. There's stuff you can do to compensate for this. If you have issue and want to discuss let me know. I'm not an expert by any means but I've been there and done that...
 

My mistake. I was looking at cam clearance instead of crank. :?

Crank clearances.
Right and left mains .006-.008

Center main .0021-.0055
 
That's right... Checked last night. The center main is spec'ed tighter because it's a thin multi layered bearing like in a car. Steel back then some sort of yellow metal then a thin layer of babbit. The .006 to 8 was for a 4" crank journal. If the 70 series have smaller journals they could be a breath tighter I suppose. The 830's took a thicker aluminum bearing and the center main is same clearance as the outers. The aluminum expands more than the cast iron and steel so you need to leave room for when it gets hot.
 

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