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Basic 2F engine rebuild questions..

Discussion in '40- & 55-Series Tech' started by offcamber40, Jul 25, 2003.

  1. offcamber40

    offcamber40

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    Ive got the head off my 40 2F right now for some head work, and was curious as to the extent of difficulty of replacing rod bearings and rings while I have the top end off. Can I just hone the cylinders and go .10 over on the rings? on the rod bearings, can they be replaced to original factory specs? The rods arent really making any bad noises, and the current compression isnt that bad, but since the head is off, I thought if there was a way to replace these and tighten the bottom end up a little and get a more even compression I would try it. Opinions? Thanks guys.

    Mike
     
  2. 73lndcrsr

    73lndcrsr SILVER Star

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    IMO if you are going to go through that much of the engine I would take everything out and do a full rebuild.

    Have the valves done, replace all bearings, including the cam, and seals. Have the crank checked. If the cylinder walls are not bad, you can just ream the ridge and replace the rings. If you think you have .010 of play then you will need to have it bored and put in new pistons. Have the cam replaced or re-ground.

    If you just want to refresh it.
    Replace the rings, bearings and seals. Inspect the cam bearings for wear.
    Hand grind the valves and put new seals on them. ream the ridge in the cylinders.
     
  3. offcamber40

    offcamber40

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    The head is off right now for a rebuild. I am going to be doing the rear main seal and clutch related stuff when I do my clutch. Im pretty much looking to just refresh with the motor still in the car. I have no real facility to pull the engine. I just figured with the top end off i would do a couple of things to try to extnd the engines life a little.. does it hurt to just do bearing and rings, or should i just leave it alone and put the head back on.
     
  4. 73lndcrsr

    73lndcrsr SILVER Star

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    Have you done compression tests? Wet and dry? What were the numbers?

    If they were both okay and the cylinders look good (no major ridge in the top)I would not worry about rings. You can check the bearings for wear, but if there is significant damage you will need to have the crank turned to make any bearing change worth while.

    Hope this helps.
     
  5. offcamber40

    offcamber40

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    I looked for the peice of paper I wrote the compression test number down on last night and couldnt fid it.. Basically, dry all cylinders were around 135-140 except for one which was in the 120s.. wet they all came up a little bit, especially the one bad cylinder.. The motor runs pretty smoothly with good power. I was getting a lot of oil smoke when I backed off on the gas after running through a gear, and also if it idled for a while. I assumed that it was valve guides and seals and that is why the head is being worked on.. the 2f only has one oil scraper seal, so I thought of doing a ring job just to ensure my oil blowby was actually in the valvletrain. BTW, on the bearings.. from what you said above it sounds like the crank wears before the bearings? I always figured it was the other way around.. so whether or not there is play in the bearings it cant be remedied by replacing the bearings, the crank has to be turned and reground?

    Thanks for the replies.

    Mike
     
  6. 73lndcrsr

    73lndcrsr SILVER Star

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    Based on your compression numbers I believe the compression in the cylinder with the low reading would be ring related. How is the ridge on the top of the cylinder wall? If it just feels like a rough spot wihtout being too thick, I would just ream it and replace the rings. In my experience, if the bearings show significant wear the crank is also being worn down. I would not want to replace the bearings to have to do it again in a few months.

    Since is sounds like you have a good running engine the bearings and crank are most likely in good shape.