Engine assembly questions (Help Urgent)

[Ron240zxt]

Got a question my engine is using Clevite 77 bearing The middle bearing is the only one with the sides on the bearings, why is this also it has a major problem fitting between the counter weights on the crank its to tight.Any suggestions on what to do here would be appreciated....Thanks for the help....

 

thanks Ron

[Guest lambsr]

I've had this happen a couple of times with L6 engines I've rebuilt. Seems the bearing manufacturers err on the min side for clearances.

 

There is a solution, but it depends on how confident you are in your met polishing skills whether you want to make the attempt. All you need is a some sheets of fine wet and dry emery paper (600 to 1000 grit) and a sheet of flat glass (float glass is best but not abs essentially).

 

Basically you need to tape or cable tie the two halves of the centre bearing together 'end-to-end' (as they if they are installed in the engine). Make sure the end (thrust) faces are flush - simply pushing them against the glass should do this (the tape or ties should be tight enough so they don't move easily).

 

Place a sheet of emery on the glass and wet it with a fair amount of clean water (you'll need to keep the sheet wet throughout). Take the bearing assembly, place it on the emery an start lapping the thrust face using a circular motion with light pressure. After each, say, 6 'circles' rotate the assembly 90 deg and continue....and so forth. The bearing assembly then needs to be turned over and the process repeated on the opposite faces. Always remembering to keep the emery wet.

 

Now your asking yourself...'how long should I do this per side ??' Unfortunately this is difficult to answer because it depends on too many factors (grade of paper, pressure..etc). What I would suggest is that you start slowly and check the bearing fit at regular intervals until you've got the clearance within tolerance. I used 1200 paper for a recent engine and it took ages.

 

The above method will work and is standard metallurgical practice for grinding samples for polishing. However, be VERY careful to wash the bearings thoroughly after each 'lap' session - emery and cranks do not mix. Simply use copious amounts of running water.

 

Good luck.

 

[Of course, you could always try another set of bearings

 

]

[240Z Turbo]

Ron, I personnaly would not touch the bearing surfaces. They are specially preparred surfaces that should not be jacked with. If you are having clearance problems with the thrust bearing then you need to send it back and get the correct one. Don't get in a rush to slap this motor together or you might regret it. If you must, take the crank to a machine shop and have them do some measurements on the crank to determine if there is a problem. You should have some clearance in the thrust bearing for the crank or you will potentially wear out the thrust surface on the bearing.

[Guest lambsr]

'specially prepared' ?? - they are surface ground on a production machine. The hand lapping method I've described will produce at least as good a result. and in most cases better. This is not rocket science, but in fact a more common practice than you seem to realise. But as I also said if he's not confident, he shouldn't do it.....simple.

 

I'll ignore the 'slapped together' comment.