Rod babbit resizing
- Thread starter Richie R
- Start date
BRENT in 10-uh-C
Well-known member
"Back in the day" you likely found people doing the same as today, ...trying to use a bad idea to correct a problem.
Think this through, ...you have a connecting rod of a certain size bore along with a pin that has now been machined to a smaller size. Let's just use the number of .010" as that smaller difference in size. By you grinding the cap to tighten that clearance you can likely get to .001" at the 12:00 & 6:00 position however you still have .010" clearance at the 3:00 & 9:00 position. Also factor in at the 5:00 & 7:00 position you will have about .003-.004 clearance, - all which creates an extreme loading on the Babbitt in the 12:00 position. When this happens you will likely see quick wear and premature failure. My suggestion is get a newly poured rod and correctly fit it to the journal pin.
hardtimes
Well-known member
Hey Richie,
X2 ! Do a drawing , and what has been said will become apparent. However, if you are just experimenting and want to use the engine at very low speed , say from the barn to the house...might last longer. Back in the day, people used leather 'inserts' in place of broken out Babbitt. Don't think that you would want to go that far in experimentation, but IMO many would be amazed at how long some jiggered up 'farmer fix' would last. I've taken down flatheads with cardboard shims and behind worn inserts. It's interesting to think about how you/we would get along without !
X2 ! Do a drawing , and what has been said will become apparent. However, if you are just experimenting and want to use the engine at very low speed , say from the barn to the house...might last longer. Back in the day, people used leather 'inserts' in place of broken out Babbitt. Don't think that you would want to go that far in experimentation, but IMO many would be amazed at how long some jiggered up 'farmer fix' would last. I've taken down flatheads with cardboard shims and behind worn inserts. It's interesting to think about how you/we would get along without !
Hi Hardtimes
I understand what you say, the bearing babbit shape would be egg shaped, but a used bearing insert shell on most insert style engines had pulled apart were worn on the top and bottom of the bearing, not the side,,,
By grinding the cap this should almost round it back up?
I was reading a old book on old Diesel engines and this technique was one of the way the slack was taken up.
hardtimes
Well-known member
Yeah, egg shaped..no yoke
The wear on top/bottom that you speak of is where most of the of forces/stress of combustion exist! With the enormous costs of rebuilding these 80 yr old engines these days, I wouldn't do any re-engineering
unless I had the machinery/talents of say George. I know nothing of diesel engines...except that they seem stronger and have less parts than four cycle gas engines. Oh, and emit horrible smelling emissions !
Tom Wesenberg
Well-known member
Even though most wear is top and bottom, you did mention turning the crankshaft undersized, so this will still induce excess clearance on the sides of the same bearing.