STU HARVEY 10/15 June ’83

Rod Barber, our worthy Chairman (Ed’s Note – and Editor!) has just been obliged to strip his PI engine after only 32,000 miles since a total rebuild. Having examined the main and big end shells I can see an advanced state of wear for such a low mileage. Assuming that the machining and reassembly was correctly carried out – it ran very well and quietly up to a few weeks ago – what exactly happened is a mystery.

The only explanation I can put forward (and have seen like before) is that some residue of “swarf” from the machining process has remained in the oilways of the block (from a rebore) and / or the crankshaft (from a regrind). In my experience some engineers specifically tell you to clean out all the oilways yourself, and some say “nowt” , and some say that the remachined units are ready to be rebuilt. Being a cynic (and a coward) I always thoroughly clean all the oilways and channels etc. I was told once by an engine specialist that the best method is to use a hot water, high pressure jet. If possible I use this but have resorted to garden sprays, bicycle pumps, etc. as available. The main thing is to get all the muck out of the oilways as it is a mixture of emery dust, carborundum grit and particles of the metal removed by the machining process – not the ideal “running in” compound. The hot water for cleaning can be blown out with compressed air or displaced by pumping clean oil through the oilways (an ordinary pressure type oil can will suffice).

While carrying out this operation don’t forget the small holes that feed the rocker shaft. Also remember that the hole is continued up through the cylinder head and any valve lapping paste or grit from valve reseating operations must be removed . This of course may have nothing to do with Rod’s trouble, but it does seem possible that something nasty may have been left behind.

When discussing this aspect of Rod’s engine at a recent Chiltern Group meeting, Chris Witor inspected the bearing shells and whilst agreeing that my theory could be the possible cause, asked why we were using Glacier bearings and not Vandervell, which he reckons are of much better quality and last a lot longer, but do not cost any more. (They do cost more nowadays! – Uncle Stan Part).

By the way, I heartily endorse the advice given in the last issue to replace the oil pressure relief valve plunger and spring periodically. The seating does wear, in which condition it could contribute to “late” oil pressure delivery.