My Tractor Forum banner

1 - 3 of 3 Posts

·
Registered
Joined
·
443 Posts
Discussion Starter #1
Anyone know when LB made the change from the slotted hex rod bolts with lock plates to the Allen head type? Most of the newer (90s) F engines I tear apart have the Allen type bolts, and most older (70s, early 80s) F engines have the bolts with lock plates. All C and D-series with needle bearings on the big end (1962-late 70s) I have worked on have had the old style bolts....except 1. My 1977 LB 5269 (with 1979ish D-570) has the newer bolts. The rod caps themselves are different because of the provisions or lack thereof for lock plates. The threads into the rod are also different between the two types. My question is, did they make replacement D-series rods with the Allen head rod bolts and no lock plates? As far as I know, you can't put a F rod in a D engine due to the length, so I wonder why my D-series has the newer bolts and rod cap with no provisions for lock plates. I hope my rambling made sense, I am just thinking out loud.:fing32:
 

·
5K Poster!!!
Joined
·
5,141 Posts
Well, your "D" engine was probably made after the change took place. OMC continued to build "D" engined well into the 70's and even the early 80's.

I actually like the older style with the lock tab but when I am working with the newer allen head style I always put a drop of threadlock blue on each bolt. Remember, torque values are extremely important when tightening rod bolts on small engines....ask me how I know..lol.
 

·
Registered
Joined
·
443 Posts
Discussion Starter #3
Yeah, the change seems to have taken place sometime in the early 1980's. I don't know much about the history of the engine on this mower, but I know for sure it is NOT original because someone swapped it from a snowblower. I've never looked inside of a LB 5006 or something similar with the last of the leftover D-series engines, but I'd like to know what type of rod they originally had. I don't have a preference as to which type I use. The Allen head bolts seem to be an interference fit thread and fit a little better, but the older type with lock plates can't back loose once the lock pate is bent over. I guess both are good designs.
 
1 - 3 of 3 Posts
Top