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Oil pressure how low is too low?

RoadRacer4Life

Owner: DeathWagon
300+ Club
Joined
Jul 3, 2005
Location
Montgomery Alabama
The oil pressure in the ole Champ wagon has never been stellar but I was curious what's considered too low.

Hot oil pressure is like 15psi at idle 800-900rpm
Hot oil pressure is around 40-45 psi at 5000rpm.

Time to build it?
Replace oil pump?

Already recently replaced oil feed tube seals so I doubt that's an issue..


-Sam
 
It's on the low side, but not dangerously low, motor is tired, not shot. what weight oil? I used to up the weight or add STP type additive to buy time
 
I've always heard the 1psi per 100 rpm at hot idle was about the minimum before it would give up the ghost. You're getting pretty close to that. Time for Lucas?
 
Different kind of how many psi can a stock support

In our race car we ran 20w50 Castrol, later squirter block. Hot we had about 20psi, and at full chat it would just tickle 50. We do have fresh bearings in the bottom end, though, for what that's worth.
 
My rebuilt squirter with new bearings and oil pump seems to run 20 at idle and about 45-50 psi above 3k. VDO gauge/sender. 15W-40 diesel oil. It does drop on long left hander turns.
 
On my recent rebuilt engine, its running 10 at hot idle and 50 at 3000 rpm. I believe has something to do with oil cooler. I did shorten my oil cooler lines and that helped. I was told running 10an lines are to big and if I switched to 8an oil pressure would increase. I think my engine is fine, I do run my idle up higer than most to keep oil pressure from dropping to low. I know rodders like low idle to hear the cam loping. But even in a ford you oil pressure drops big time.
 
With redblocks I've just come to not worry so much about oil pressure so long as the light doesn't flicker at idle or drop below 1 bar (~14psi) on a hot idle. B18, B20, and B230 motors have already a wide variety of oil pressure values for me. Usually on the lower end when hot even with thicker oil (15w40 or 20w50) and a relatively fresh motor.
 
Main and rod bearing clearance, will be the key to oil pressure, and oil pump out put volume is another factor . Small oil lines to cooler/remote filter restrict oil flow. I run -10 lines on the V8 car with remote oil filter [1&1/2 quart] and 16 row oil cooler. My MG Midget 1275cc runs -10 lines, remote oil filter,13 row oil cooler, 70psi hot @ WOT [8,500 RPM] I,m going to up the pressure relief valve. Bearing clearance and oil pump out put and volume are the key to oil pressure. A good rule of thumb is 10 lbs per 1000 rpm The Midget runs 40 lbs at idle hot @ 1,100 RPM.
 
Noticed a drop in pressure when I swapped in the RX7 cooler. Needed new fittings, ran 1/2" push-lock hose from the stock hardlines to the RX7 banjo's. Factory squirter, hot idle with decent bearing clearances and an M181 pump, running 10w40 M1 is around 1.8-2b, hot cruise at around 2600 is around 2.8b, hot 4500rpm is around 3.2b.
 
My stock B21ft in the flathood runs low at hot idle, but the light never flickers- it has had bearings and pump done in the past.
 
We ran a full day of endurance racing with a paper towel jammed in the oil pump inlet, running 20-23psi at wide open, high RPM. Rod bearings looked great! 15 at idle is just fine.
 
From my yellowing 1985 GLT Owner's Manual:

85-GLT-Oil-Warning-Light.jpg


85-GLT-Oil-Warning-Gauge.jpg


My original ~350K miles B21FT engine definitely flickered at idle when hot. My rebuilt B21FT doesn't flicker, but the hot idle pressure is certainly way on the left of the gauge. And yes, the pressure noticeably drops when the oil cooler thermostat opens.
 
I ran my NA B23 for about 8 months/10k miles with 15w40 oil with the oil pressure at about 8psi@idle/35psi@3-4k. The oil pressure light was on solid until about 1500 rpm and it ran fine until I pulled the engine so yours probably won't blow up or anything
 
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