1968 S1.5 Crankshaft.

[mikebryan]

I am restoring a 1968 S1.5 OTS. Have recently stripped down the engine and have the crankshaft out. The crankshaft shows some scoring on the main bearings, whereas the big end bearings are within spec and have no scoring.
Would appreciate some advice re. the main bearings.

According to my workshop manual, the spec for the main bearings is, 69.85 to 69.86 mm.

The journals are Nr. 1 69.81mm
Nr. 2 69.83mm
Nr.3 69.85mm
Nr.4 69.82mm
Nr.5 69.82mm
Nr.6 69.84mm
Nr.7 69.80mm.
So, yes they are out of spec, but only marginally and also they have a few scratch marks. My problem is that I live in Munster Germany and so far have been unable to find a qualified Jaguar engineer who could advise me. The bearing shells that I have taken out are standard size. Would appreciate any input,

Thanks

Mike

[PeterCrespin]

Your worst main is just under 2 thou down. The engine will run OK with mains merely polished IMO but not be as good as new. Polish all journals and run the thing if:

1) Money is really tight
2) You do your own work and can handle an earlier rebuild than if you spent more
3) You merely intend to do a thousand gentle miles a year.

If you wish to use the engine hard, or 'fit and forget' with only one set of outside labour charges, do it once and do it right.

The plugs need to come out of the crank anyhow, and since you need new shells the undersize will cost no more. Which only leaves the regrind charge and only for seven journals. The rest is just opinion and everyone has one. Seems like false economy to skip it, unless you are really stoney broke and just want to potter around. But you knew that anyway I guess.

Pete

[christopher storey]

I agree entirely with Peter. The expensive part of refurbishing the bottom end is the bearing shells, which are expensive , and if the journals are scored however lightly to a depth which polishing will not remove , the scoring will damage the new shells very quickly . Any competent machine shop will be able to regrind the mains for a modest cost - here in UK the last time I did it it was about £ 13 per journal, say 15 - 20 euros, and you would be best letting the machine shop guide you as to how much needs to come off . It sounds as though .010" = 0.254mm undersize will be good enough but it is best to wait for the machine shop before ordering new undersize bearings . I also emphasise my agreement with Peter about the plugs being removed from the crank webs - it is amazing what comes out of the drilled passages when these are removed, and it is also sad that many people neglect this and then wonder why their new bottom end is wrecked by the abrasive material finding its way into their brand new bearings

[mikebryan]

Hi
Thanks for the replies, and especially regarding the removal of the plugs, which I was not aware of. Will continue to hunt down a competent machine shop over her. Thanks again guys

Mike

[abowie]

Do it properly and do it once. If you have scratches and scoring I'd get it reground 10 thou under.

A set of main bearings costs bugger all in comparison to the effort of rebuilding the short motor a second time. A regrind of the mains and polishing up the big ends is similarly not much. Any competent machine shop will be able to do this for you.

Removing and replacing the sludge plugs with new ones is a must. They are usually peened in with a punch. They can be removed carefully with an appropriate allen head socket on a racket. Once the plugs are out thoroughly clean out any crud in the oil ways. I gently chase the threads with a tap before I put in new plugs. I use blue Locktite on the threads and peen them as well.