Car in bits again...
AO Silver Member
Join Date: Feb 2007
Location: Hampshire, UK
Hi Al - I can only think of one more top end issue that has happened to me, and that is when my cambox gasket let go on the LH cylinder bank. This is the thin plastic sheet that goes between the cambox and the cylinder head. When it is working the oil level in the cambox only drains back to the level of the return holes, leaving the camshaft and tappets partially submerged in oil.
When the gasket failed it allowed nearly all of the oil in the cambox to drain back into the sump, leaving the camshaft journals and tappets on that bank starved of oil at startup.
Probably not related to your situation if the engine is a fresh build, but I went against advice and used sealant on this gasket just to be on the safe side (Stag Wellseal). Unfortunately with a hydraulic engine you can't take the cam covers off to see where the oil level is at.
I would definitely agree that the oil level in the camboxes will be dictated by the orientation of the engine. But the bottom end should not suffer from oil starvation in the same way, as the oil pump pickup is too deeply submerged in oil. Good oil pressure means the strainer is not clogged, and you don't have air leaks ahead of the pump, or blockage in the filter.
So I can't think of what might cause the bottom end to knock, unless it is an unrelated issue (flywheel bolts loose? That happened to me once).
The valve in the oil filter blocks the oil in the main oil gallery (on top of the block) from draining back to the sump too quickly, although as Kev says, nothing will stop this happening eventually. Normally though the oil viscosity prevents it flowing freely past the clearance gaps in the pump impellor etc.
The only other possibilities are excessive clearance around the main bearing journals, letting the oil out that way. How long does it take for oil pressure to develop? Is the oil light on for a couple of seconds after the engine fires?
Hope you can get to the bottom of it soon!
Alfanauts are GO!!!