My long running engine rebuild is on again and I have a few issues. Its a 1990 1275 Rsp cooper with the original 12A MG metro engine. I've kept it standard as bores & pistons are fine but I'm fitting new bearings & rings as part of a complete stripdown & overhaul due to an earlier gearbox problem.
1) I gapped the new rings today but I'm finding variation, especially with the second ring (although top rings may have the same problem as Ive only measured 1 of these so far). They are Grant rings made in the USA & are supplied in separate packets for 1, 2 & oil control.
I set the middle rings 2.5 inches down no.1 bore using a piston to set them square. I also confirmed using a vernier to measure the depth. Of the 4 rings in the set one is bottom spec (8 thou), one is top spec (13 thou), however the other two are measuring at 18 thou. I've tried the ones with the 18 thou gap in no.2 bore with the same result. As a further check I set them 5 mm down the bore above the ring land & they measured 17.5 thou. Are these two ok to use?
2) Crank end float. I measured this using a dial gauge on the end of the crank & measured it at 3.5 thou. I thought this was ok, however the Haynes manual says 2~3 for the 12A engine so I tried a set of +3 thou washers but the crank was tight to turn by hand. So I reverted back to my original standard washers. Again is 3.5 thou ok?
3) Following AndyMiniMad excellent rebuild guide on this forum, Andy oiled the back of the main bearings before installing, however a couple of people advised against this & suggested installing them on a cleaned surface stating 'the bearing could possibly spin'. Unless I've missed something its not possible with mini shells as the opposing tangs will prevent this. Are there any other reasons not to oil them?