Replacing mains bearings

[beepbeep]

Further to my previous post I've removed the sump and the rear mains cap to replace the oil seals. The main bearing is a little bit scored and I'm thinking of replacing the bearings while I'm on (I changed the rod bearings last year). Am I right in thinking this can be done in situ? The front cap looks a bit awkward to remove but is it do-able without removing the crank pulley and timing cover etc?

Chris

[June J]

Hi Chris,
yes, you can change the main bearings in situ. Remember to release all the main bearing cap bolts to allow the crankshaft to drop a little to make things easier to remove the old bearing shells. Its a good idea to get a brass plug made up that fits into the oil hole in the crankshaft, and that protrudes from the shaft slightly LESS than the thickness of the bearing shell. You use this to carefully remove the old upper bearing shells by rotating the crankshaft, thereby avoiding any damage to the crankshaft or bearing cavities in the cylinder block.

Be careful when fitting the bearing caps, make sure they engage in the rebates in the cylinder block before making up the bolts, I have seen caps cracked by folks not checking this before making up the bolts.

Good luck.

Ian

[beepbeep]

Thanks for the reply Ian, so I just loosen the caps enough to allow the crank to drop a little but not take them off completely for the top shells then take them off individually to do each cap shell? Does the brass plug just pull the top shell round when the crank is rotated? The front cap looks as though the casting that the timing cover bolts to would have to be removed in order to loosen the bolts, does that sound right or can you get access without doing that? Thanks

Chris

[Kaegi]

never seen the phrase "in situ"?? an abbreviation for something?

[beepbeep]

I didn't know so I had to look up where it comes from and it's from the Latin for 'in position'......must be a British thing

[Kaegi]

I didn't know so I had to look up where it comes from and it's from the Latin for 'in position'......must be a British thing

thanks for improving my command of language. ;/)

[June J]

Thanks for the reply Ian,

so I just loosen the caps enough to allow the crank to drop a little but not take them off completely for the top shells then take them off individually to do each cap shell? Yes, it gives you a bit more clearance to ease getting the top shells out.

Does the brass plug just pull the top shell round when the crank is rotated? Yep, exactly. some folks try to push the shells out with a screw driver, in doing so you risk damaging the crankshaft or bearing pocket

The front cap looks as though the casting that the timing cover bolts to would have to be removed in order to loosen the bolts, does that sound right or can you get access without doing that? Its been a while since I did mine but that certainly sounds right. I seem to recall cutting the old timing cover gasket and gluing in a new piece where the cast bridge/sump front cork bridge attaches believe it or not it didnt leak!!!
Cheers

Ian

[June J]

Chris,
Google "Crowsfoot Wrenches", there are a number of brands listed at quite reasonable prices. You may even be able to buy a single 5/8 wrench.
Cheers

Ian

[beepbeep]

I didn't know so I had to look up where it comes from and it's from the Latin for 'in position'......must be a British thing

thanks for improving my command of language. ;/)