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Oil Pressure

Ken56

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Lk. Ariel, Pa.
I have a 66 Belvedere with non original modified 440. Oil pressure is between 70 and 80Psi when first started, After warm up it drops to 18 or 19PSI @ idle. Should I be concerned?
Thanks, Ken
 
18 or 19 psi hot idle is OK, sort of marginal for me personally but also depends on what viscosity oil you are using and your idle rpm. Also, if the car is an automatic and that’s in gear I would not worry about it. I usually try to maintain 20 psi hot in the summer and adjust my oil viscosity (within reason) to adjust. But I don’t think most oil pressure warning lights come on until something like 5 psi or less.
 
Old rule of thumb is hot oil pressure 10 PSI per 1000 rpm.
18-19 PSI @ 800 RPM is fine in my books.
 
At 20 psi warm, it's a little lower than I like, but it really does depend on what oil you use. Some oils do start out "thicker" then thin out. What does it come up to at 1800 RPM? A bit of wear on the oil pump rotors will change that 800 RPM idle number a fair amount. A good real tight oil pump will have more. If you are at about 40 PSI at cruising speed you are just fine.
 
Got a hole new oil pump from Summit. No worries now. Not that expensive.
 
Thanks for all the replies, I asked because I also have a 68 Roadrunner with it's original 383 and has a higher oil PSI. It's over 80 @ start up, and well over 20 @ idle when hot. The Beledere is a 4 speed and I run 10w-30w high zinc PennGrade in both cars.
 
Remember pressure readings are resistance to flow.. Low Idle oil pressure is the result of the pump flow volume not being able to keep up with internal leakage. As engine speed rises flow volume increases. As long as the high rpm pressure is a desired number you are good. 10 psi/1000 rpm is plenty safe.
Doug
 
Brand new build, 440 +0.60 over stand oil pump, only done about 1500 miles so far,
60psi running at 60mph and 20-30 at idle,
High volume/pressure pump did 80 at start up. everyone has different ideas, my engine guy said 80's to much and so that's back at 60 with std pump
 
I have had a 67 GTX clone for 12 years now with a 440 RB engine. The engine stamp is 02/68. My oil pressure starts at 25-30 psi on startup and gets up to 80+ when warm and running. I have been using Valvoline Hign Zinc racing oil at 20W-50. No smoke, no leaks, runs smooth.
 
I have a 66 Belvedere with non original modified 440. Oil pressure is between 70 and 80Psi when first started, After warm up it drops to 18 or 19PSI @ idle. Should I be concerned?
Thanks, Ken
What are your bearing clearances etc? The more clearance is, the chances are your oil pressure will be a bit low at hot idle.

Brand new build, 440 +0.60 over stand oil pump, only done about 1500 miles so far,
60psi running at 60mph and 20-30 at idle,
High volume/pressure pump did 80 at start up. everyone has different ideas, my engine guy said 80's to much and so that's back at 60 with std pump
Don't think 80 cold is too much.....been there lots of times and it comes down a bit once at op temps.
 
Brand new build, 440 +0.60 over stand oil pump, only done about 1500 miles so far,
60psi running at 60mph and 20-30 at idle,
High volume/pressure pump did 80 at start up. everyone has different ideas, my engine guy said 80's to much and so that's back at 60 with std pump

It all depends on what the bearing clearances are and what weight oil you are using. 80 psi is not too high with heavy oil to start out, I presume it dropped some after warming up. Standard pump is probably just fine if the bearing clearances are like stock. 60 psi at 60 mph is just fine, 20-30 at idle is in the ball park.
 
I have had some motors that had 70-90 cold and 50 at warm idle and 60-65 at 2000 rpm. I have also had some with 70 cold and 20 warm at idle. 35 at 2000 rpm. My race engine pegs the gauge at 100 cold. Warm idle 70. Going down the track pressure is pegged again. I have had 1 motor that was 60 cold and 40 warm and 50 at 2000. Kim
 
I have had some motors that had 70-90 cold and 50 at warm idle and 60-65 at 2000 rpm. I have also had some with 70 cold and 20 warm at idle. 35 at 2000 rpm. My race engine pegs the gauge at 100 cold. Warm idle 70. Going down the track pressure is pegged again. I have had 1 motor that was 60 cold and 40 warm and 50 at 2000. Kim
Do you recall bearing clearances on them?
 
They were all .002 to .0025 on the rods and .003 on the mains. Cam bearings were also changed. I built everyone. I will say that I don’t like seeing anything less than 30 lbs at idle. They all have been fine though. Maybe some had more of a restriction in the block and heads or the lifters. Kim
 
383 Stroker - 440 Source

.0025 clearance on the mains - Block line honed using 440 Source Billet Main Caps

25 PSI oil pressure at 700 RPMs hot idle

I always wondered what effect full groove main bearings had on oil pressure or flow if any
 
Pressure is nothing but resistance to flow. It is dictated by pump volume (speed dependent), internal leaks (clearances), oil viscosity (temperature dependent). Knowing this makes it easy to see why low engine speed, warm or thin oil, and larger clearances lower pressure. So the only question that reminds is how much pressure is enough? Age old rule of thumb is 10psi/1000rpm. For most engines this is an extremely safe number. Do you need 50w oil. Most likely not unless you run extreme heat thinning your oil. Watch the gauge it will tell you. Pressure to low at higher engine rpm? You need a stiffer relief spring. If that doesn’t do it, you need more pump volume. To low at idle? Don’t worry about it. If you recorded actual idle oil pressure in new vehicles you’d have a heart attack.
Doug
 
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