Sean---The only thing that tells me that there is some "looseness" in
your oiling system is the 50 lb. @ 3000 rpm. This is generally from a
larger than ideal gaps between the rod and main bearings and the
crankshaft. (Altho less likely it could be from a worn oil pump)
The 15 to 20 lb. seen at hot idle should not be troubling.
The other part of this is what one may call "hot idle". If this is when
the coolant temp gets up to normal, such as when driving around town,
the oil is probably not to its thinnest viscosity. This only occurs with
sustained highway driving, or during competition. It's not unusual for a
good engine to have its oil pressure to drop to 15 lb. at these times.
Cold oil pressures don't mean much, as this is the product of many
things that may have little to do with engine conditions.
If you feel you want to bring up the oil pressure readings that you now
see, and the crank journals look OK and measure within specs, then just
replace the bearings.
If the engine is otherwise OK and not pumping out too much oil, you
could just drive it a while longer.
Dick
From:
mccafferty@sympatico.ca(Sean McCafferty)
Hello,
The winter project season has started - snow's in the forecast for later
this week.
When driving this summer and monitoring my oil pressure the typical
readings I was getting were: 70-80Ibs cold, 50 lbs @3000 RPM- 4th gear
and 15-20lbs hot idle. The last reading was the one that had me
concerned and so main/con rod bearings and thrust washer assessment were
put on the project list. I dropped the pan this past weekend and pulled
the #6 con rod bearing. Everything looked good to me - minimal, if any,
wear on the bearing. Crank also looked good with no scoring on the
bearing surface. I checked the oil pump specs to the Bentley standard
and they also look good - the outer rotor to the pump body was on the
outer end of the acceptable .010 so I'll go ahead and replace the pump.
The questions I have are:
- most of my reading suggests 15-20lbs hot idle is low ---
is there a
specific circumstance that would cause that?
- the bearing I removed was Std dimension (no manufacturer
marks) and the new ones I ordered were the BPNW tri-metal so I hate to
have them sit around and collect dust - if the surfaces look good do I
really need to plastigage the fit to check whether the fit is within
spec or just go ahead and install the new bearings?
Any suggestions/recommendations would be appreciated.
Sean McCafferty
Milton, Ontario
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