Engine Rebuild Question

[Rick ('50, NC)]

I have a '50 Cub that has low oil pressure after getting hot. I am using 20W-50 Full Synthetic Oil that holds the oil pressure at about 18 pounds while mowing in Summer heat. It does not use oil, and only smokes a little at start-up. Then never smokes any more until the next cold start-up.

My questions:

1. Does this sound like cam or crank bearings?
2. Can the cam and crank/connecting rod bearing be replaced without pulling the engine from the torque tube?
3. Do you have any more insight into this situation?

Thanks for any input.

[Dale51]

This is just my $.02 but the first thing I would do is try a diff. oil pressure guage.
When did you switch to synthetic & did you have this problem be for the switch?
The reason I ask is that some old eng. like synthetic others hate it.
After turning the wrench for 12 years on cars I found that a new eng. is fine with synthetic but with old or used eng. it caused more problems than It was worth.

Also what is you pressue when cold right after start up ?

As for the rest the rods can be done with torque tube on the rest can not.

[Rick ('50, NC)]

Dale,

The pressure is about 35 psi at start-up and slowly drops to about 18 psi after mowing 30-45 minutes. I switched to full synthetic because I was told that the oil would not lose viscosity as much as petro-based oil after it got hot. The pressure was lower with standard 15W-40 oil after getting hot.

The only reason I hesitate to do any engine work before asking for advice is that the pressure doesn't behave like I would expect it to if bearings were worn. At mowing RPM after reaching operating temperature, oil pressure is about 18 pounds. At idle it is still about 8 - 10 pounds. I would expect the oil pressure to drop to almost zero at idle.

What do you think?

[Bigdog]

Rick, I think it will run a long time with pressure readings like that. Based on your description of no oil consumption and only minor smoke at start-up, I wouldn't do anything at this point. (Unless you just need something to do.)

[Dale51]

Rick, I think it will run a long time with pressure readings like that. Based on your description of no oil consumption and only minor smoke at start-up, I wouldn't do anything at this point. (Unless you just need something to do.)

I agree with Bigdog at this time I would not do anything.
Just keep er full of oil & watch the guage.
OH and most of all have fun while you use your cub.