Re: If you were to overhaul your engine...

Posted by Larry51 On 2014/3/16 7:48:48

Definitely rings, timing chain (as you said), and other parts that have worn to well beyond the mid-point of their measurement/ tolerance specs. Especially bearings (oil pressure limitations)and valve guides (leak down). And oil pump must be in spec of course.

Camshaft wear (pitting especially) can't be tolerated and valves that have thinned due to many re-facings likewise.

I'm sure opinions vary regarding re-boring and other major work but my opinion is measure carefully and make a decision based not only on wear but also on 1) how rapidly the engine has worn during past use, and 2) how much you are willing to spend!

If you've done many miles and engine wear has been minimal then why re-bore etc at the mid-point tolerances when you may get many more miles with just a set of rings and regular oil changes? (That's my philosophy, not being wealthy!)

I'm sure that for some, anything other than 'new spec / minimal tolerance' is not acceptable. But if a new valve guide causes a valve to jam then a bit of wear in the original guide would probably have prevented that situation, at the cost of a bit of extra oil being used.

Regarding assembly lubricants I think a spray of Molybdenum Disulphide on every moving surface is a good idea - even necessary. Adding a slip agent (oil modifier) to oil is a good idea as well - unless you are 'running in' a re-bored block, in which case you don't want a slip agent during the running-in period.