Bottom Half of Motor

[rgreen]

Is it feasible to do the bottom half of the motor first before you do the top half few months down the road. I have read on other post but no on here. Where some folks was doing the bottom part of the motor then waiting a while then doing top half of the motor. Also what's all done when you just do the bottom half of the motor???

[Texasdude74]

Bottom half consists of liner kits, rods/main bearings and the oil pump. Usually the top half (head and cam) wears out first. You'll be paying for a lot of labor twice by doing only one or the other. Usually someone does only the top or bottom half when one end or the other has something fail prematurely.

[Hammerhead]

I don't like the demarcation of "Top Half" and "Bottom Half" of a motor.
IMHO, a motor is best divided into thirds.
Top Third:
Everything from the head gasket up. If your head or cams are worn and this is what you replace, then you are not disrupting the bottom two thirds.
Middle Third:
Liners, pistons, block, connecting rod from the crank bearing up. This section of the motor cannot be accessed without undoing the other two thirds, but the other two thirds can be done without touching this or each other section.
Bottom Third:
Rotating assembly down. Rod bearings, main bearings, crankshaft, oil pump, etc. This section can also be serviced without disturbing the other two sections.

When you divide a motor in half, you can't service the liners, pistons, and such without removing the top half. The traditional phrase of "doing the bottom end" usually means rod & main bearings, and occasionally the oil pump. Doing only this is fine if you have inspected the liners with a boroscope. But if your planning to do this, and the top third, then it's just best to do a complete inframe at one time. There's no sense in doing bottom end bearings, then a short time later planning to do the top, you're buying the same parts and labor twice doing it that way.

[rgreen]

(01-19-2017 )Hammerhead Wrote:  I don't like the demarcation of "Top Half" and "Bottom Half" of a motor.
IMHO, a motor is best divided into thirds.
Top Third:
Everything from the head gasket up. If your head or cams are worn and this is what you replace, then you are not disrupting the bottom two thirds.
Middle Third:
Liners, pistons, block, connecting rod from the crank bearing up. This section of the motor cannot be accessed without undoing the other two thirds, but the other two thirds can be done without touching this or each other section.
Bottom Third:
Rotating assembly down. Rod bearings, main bearings, crankshaft, oil pump, etc. This section can also be serviced without disturbing the other two sections.

When you divide a motor in half, you can't service the liners, pistons, and such without removing the top half. The traditional phrase of "doing the bottom end" usually means rod & main bearings, and occasionally the oil pump. Doing only this is fine if you have inspected the liners with a boroscope. But if your planning to do this, and the top third, then it's just best to do a comets inframe at one time. There's no sense in doing bottom end bearings, then a short time later planning to do the top, you're buying the same parts and labor twice doing it that way.

Thank you... I was just reading and I had friend tell me that he was go get his bottom third done. He can get more miles out of his truck, so I was having a debate with him. Which didn't
make sense to me and he has over millions miles on his trunk...

[Hammerhead]

(01-19-2017 )rgreen Wrote:  Thank you... I was just reading and I had friend tell me that he was go get his bottom third done. He can get more miles out of his truck, so I was having a debate with him. Which didn't
make sense to me and he has over millions miles on his trunk...

If his liners still have good crosshatching in them, and his head isn't worn out, then yes rolling in a new set of bearings is a very good idea with that many miles on it.