Howard, I was interested in your comments on the Stag issues re the OHC and your thinking on periodical start up`s and that you determined those as being the cause of premature bearing surfaces in the cylinder head.... ? I am not in anyway suggesting you are incorrect in your assumptions, though as I typed in my ramble in terms of oil drain down, it seems once drain down may have been thought to be an issue in early adoption of OHC engines in mundanemobiles, that oil companies may have altered the formula in the make-up of their oils to try to overcome drain down to some extent...?
I suspect today that there may be numerous types of oils available and that some vehicle manufacturers are very specific relative to the exact specification of oil required to suit any particular engine. For sure there will be some sort of marketing tie up between oils and vehicle manufacturers as one might expect but Engines and their the manufacturing tolerances have changed since the time my mid 80`s +8 hit the road. I suspect with more accurate and perhaps tighter bearing clearances that some degree of drain down may have been accomplished, to the extent that "thinner" oils may be used such as the change over to synthetic oils for most modern vehicles...?
In the case of your Stag Howard, perhaps dependant on the actual circumstances at the time, the time between start ups and the oil in use there was enough time for the oil to drain from the cylinder head between every start up, equating to an oil starved cam on each and every start up, which using my logic, would seem to equate to excessive wear and eventual failure..?
There are numerous theories as how best to maintain a classic during times of lay-up and I guess that may differ to some degree dependant on the age of the engine design. I suspect those engines of an age designed to run on synthetic oils may indeed need little in the way of semi regular start ups, assuming the correct grade of oil is used in the engine and preferably a known quality brand if not that which the manufacturer specified..?
I know of one 993 owner who lay`s up his car for months on end and supposedly just jumps in turns the key and drives off...whereas some with similarly aged Porsches remove a relay to inhibit the engine firing up, and crank it over till the oil pressure begins to rise before putting the relay back in and firing it up...As ever each to their own (-:
While typing of oil.... When touring some years back and finding it difficult if not impossible to locate Castrol at French service stations, I did spot a can of STP oil treatment, which when added to the old +8 considerably reduced it`s usual thirst for oil.... Yeah I have read that STP may have other issues, but circa 20 years on my old +8 still seems to be running just fine... (-:
