Subject: V12 motor overhaul
This is information from Mark Whitehead which I think helpfull for all V12 users:
regarding your request for information to access parts for an overhaul we would like to tell you what we did in the overhaul of the 7 engines.
1. we fitted new original V12 pistons of which we had a set, but wondered why as the old pistons were near to perfect. On subsequent engines we found also the pistons were in as new condition, no wear on the skirt and also the ringlands so we had them cam ground, fitted new rigns and reused them.
2. in the mater of the conrods we had them crack and fatigue tested which showed no defects. We then opened out the bigends to take slipper bearings.
3. We had the crankshafts crack tested, do defects, reground and then built up with hardchrome and machined back to original size. New main bearings fitted and linebored.
4. Valve guides we reused as they do not wear, the camfollowers ensuring that the thrust is centric. Valves we were able to obtain new from Morris Leo who then had a stock of new valves but once he gave up Lagonda work the residue of parts were acquired by the late Ivan Forshore whose son is now running the businesss and trading as Aston Service Dorset but we understand he has changed the business name.
The Sanction 1 engines had valves whose stems were a different length to the Santcion 2; the fact is that many engines were converted by the works from Sanction 1 to Sanction 2 and you will have to dismantle the valve gear assembly to determine which you need. Also the camfollowers differed as between the Sanction 1 and the Sanction 2, which had shorter cam acceleration ramps which changed the valve timing. The early engines were timed at inlet valve opening at 15 degrees before top dead centre and the Sanction 2 with the shorter acceleration ramp at 11 degrees before top dead centre.
5. We had the acceleration ramps on the camfollowers re radiused.
I have no doubt that the overhaul specialists in England could help locate what you require. W.O. Bentleys claim that he built these cars to do at least 250,000 miles before requiring anything but top overhauls. Our experience has proved him correct... as long as they are not abused.
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