I've been following the saga of oil pressure in TR6s and replacing big end
bearings and I have to jump in and make a few statements:
Remember, it's the job of the oil pump to deliver oil to the wearing surfaces,
and the job of the viscosity of the oil to keep the wearing surfaces apart.
The pressure that the pump developes cannot keep the surfaces apart. What
keeps them apart is that the oil can't get out of the surface's "way" quick
enough! Thus an engine can motor along on low oil pressure, I don't
recommend it, but it can (I once drove a TR3 several hundred miles on 10
psi). Don't play Speed Racer!
If the oil pressure is low in an engine due to engine wear, then adding
thicker oil to bring up the oil pressure actually does little to the
lubrication capability, but it does make the owner feel better. ( You are
just delaying the inevitable). Low oil pressure is an indication of engine
wear,and an indication of engine rebuilding time. Pay me now, or pay me later.
If you are going to all the trouble to replace big end (con rod) bearings then
measure the crank. It does little good to put new bearings on a worn and/or
scored crank. This is a good way to end up with a spun bearing as someone in
our local club will attest to. In the engines I've rebuilt when the con rod
bearings were shot the crank needed grinding to bring it back into tolerance.
Tolerance numbers are printed for a reason. Pay me now, or pay me later.
Sorry about the sarchasm, but I've been burnt too many times by people saying
"this engine's been rebuilt". To me that means "tear it apart now"!
Bruce "Paid my dues" Clough cloughbt@batman.flight.wpafb.af.mil
|