Straight 40w?

[Jim Becker]

I think you said the engine was rebuilt lately.

Hold up a minute. We need to follow this comment a little farther back. When was major work done on this engine, like how many hours? A lot of gasket sets come with an oil pump gasket that is way too thick. If one of them was used, a lot of oil will bypass inside the pump. The result is low oil pressure. You may not have a crankshaft bearing problem.

[Glen]

If you have records of when the engine work was done, and what was done to it, it would be nice to know about that. The Cub has to be split at the rear of the engine to get to the oil pump Jim mentioned above.
I don't know if you said if the oil pressure was low before the engine was repaired.

Just to show you more about it, below are pics from TM Tractor showing the Cub crankshaft.
The bearings run on the flat shiny areas, they are called journals, you can see the round oil holes for the bearing in pics 3 and 4. It is not turned right to see the oil holes in all the pics.
http://www.tmtractor.com/tm-tractor/gen ... ft_001.htm

The journals should be smooth and shiny, not rough or worn, or out of round.

Below are pics of the connecting rods, the bearings fit on the crankshaft journal surfaces.
http://www.tmtractor.com/tm-tractor/gen ... ds_001.htm

Below are pics of a Cub engine block showing where the crankshaft goes, in pics 4 and 7.
http://www.tmtractor.com/tm-tractor/gen ... 48_001.htm

[Gary Dotson]

There has been much mention about connecting rod bearings but the crankshaft main bearings play just as big of a part in the oil pressure thing. I would certainly look into the oil pump gasket, as Jim mentioned.

[Clemsonfor]

There has been much mention about connecting rod bearings but the crankshaft main bearings play just as big of a part in the oil pressure thing. I would certainly look into the oil pump gasket, as Jim mentioned.

Yes your correct mains and rods are different but I guess I was thinking of all those bearings as a whole. Yes there entirely different and do very different duties but in the end there bearings that basically encircle the crankshaft . You are correct worn mains will do the exact same thing, decrease oil pressure.

[49Cub2017]

I see a few more questions have been asked about the work that was done. Most recently, the head gasket failed, so that was what the main focus was. But, while the engine was apart I suggested other items be replaced. So, new rings, connecting rod bearings, valve train overhaul, head resurfaced, and all required gaskets to reassemble. The main engine bearings were not replaced. As to the hours run since this was done, not all that many...if I had to guess, maybe 30 or so. I have another mower and have purposely used it more I guess as a way to preserve the Cub. I have to confess, I don't know how long the pressure has been low because I only noticed it within the last few hours. While I watch for the pressure to come up when starting, I only recently noticed the low pressure after being run until hot.
I have a call in to the fellow who did the most recent work. He is a long time trusted mechanic who has worked on this Cub for years, including doing previous engine overhauls. I'm hoping I can get it back in his shop to take another look.

[Jim Becker]

I have a call in to the fellow who did the most recent work.

Be sure to ask him whether he had the oil pump off and whether he checked end clearance on the pump gears. Mention the question about the oil pump gasket.

[49Cub2017]

Jim: Will do. I’ve made a list of every one of the possibilities discussed in this thread and plan to ask him about all of them.

[Clemsonfor]

He is a long time trusted mechanic who has worked on this Cub for years, including doing previous engine overhauls. I'm hoping I can get it back in his shop to take another look.

How many "engine overhauls " has this thing had!!!

[49Cub2017]

I’m not sure, but it’s had maintenance at intervals over the years. My Father in law bought it sometime in the 1960’s and maintained about 4 acres of field with it, so I’m sure that put some wear on it. He’s no longer living, so I can’t ask him.