Surfer69

I have been fighting a low oil pressure problem at really hot idle for a while now ever since I got my rebuild back a few weeks ago. Getting off hiway and coming to a stop the pressure would be 13-14 psi. First off I have new everything in the engine and high v pump. So before I blame engine rebuilders I started trying different things to resolve the problem. Long oil filter, heavier weight oil, lucas oil additive which didnt do much maybe 1-2 psi more at best. I knew pump was installed OK cause I checked pan with clay etc. After reading here and other articles, asking SBC people the number I was looking for was 20-23 psi at a min. The other weird thing was this low p was only after high rpm on hiway, really hot around town was still acceptable. Well it turned out that rpm and temperature were the main reasons. My idle was 650 rpm this whole time and I was using 195 thermo which the service manual says to use so I thought why not. I pulled a 195 out of the engine so someone else thought it was good. Once I put a 160 in and had idle at 800-850 rpm, I now was over 20 psi. By the way cold pressure is almost 70 psi and hiway was 45. Also, idle alone would not get me over 20 psi.

Without starting a war on thermos again it should be told that my previous engine spun a#1 rod brg and was using 195 thermo. So thermostat seems to keep engine and oil temperatures at different levels even after engine is super hot. The thinner the oil, the less effective it looks like. I always believed thermo did nothing after opening but stay opened but it seems clear it is regulating all the time. Temp gage shows 30 degree difference now also, even after highway.

I know pressure could probably still be higher but I believe I can stop sweating over this and start enjoying my car again which now runs great and fast.

Matt Gruber

engine failure is caused by low oil pressure at high rpm.
when very hot, what psi is it at 4500-5000?
THAT is the number to worry about, if poor.
sometimes it will drop in neutral right before your eyes :eek:

Aflac

Smokey Yunick's point of view was 10 psi per 1000rpm...

Surfer69

I heard that too and thought maybe I shouldnt worry about idle at 650 since per that theory 6.5 psi would be good, but other people say that applies only to higher rpms.

Pressure at 4k is over 50 psi.

MotorHead

10psi per 1000RPM but I would not like anything under 20psi at idle :D


[Modified by MotorHead, 11:50 AM 9/12/2003]