Dropping Oil Pressure
Thread Starter
Le Mans Master
Joined: Jul 2006
Posts: 8,117
Likes: 104
From: charlotte north carolina
Dropping Oil Pressure
First road trip for the 427 swap into a 70. While testing and timing the engine the oil pressure was 70 when cold and then dropped to about 35 (Rotella 15-40W). After about 30 minutes the oil pressure started to drop to about 15. PANIC!! It held steady until I got home and I parked it overnight. Today I pulled the dissy lead and cranked it-nada, zip, zero. First thought was the oil pump feed tube. Pulled the dissy and used an air wrench and an old dissy that has a nut weled to the shaft and worked the pump. pressure was about 20. Whew! Dodged a bullet. I think! I replaced the original dissy and the pressure is about 20 while cranking.
But the fact remains the pressure dropped on the road trip. Any ideas?
BTW, it screams!
But the fact remains the pressure dropped on the road trip. Any ideas?
BTW, it screams!
Racer
Joined: Sep 2012
Posts: 262
Likes: 0
From: Roanoke Va.
What you are describing sounds perfectly normal. The oil is just thick when cold and as it warms up and the oil thins, the pressure will drop. As long as it stabilized at around 15 like you said, it seems normal to me. Even muti-grade oils will give you different oil pressure readings between a cold and a warmed up motor.. Drive it.
Le Mans Master
Joined: Oct 2007
Posts: 7,451
Likes: 974
From: RI, Now Franklin/Nashville TN
15 lbs of oil pressure is way too low! My 78 L-82 runs about 40 lbs cruising down the road at 2,500 RPM and 50 PSI at higher RPMS when hot. 30-35 PSI at idle when hot. Just changed the oil Sat with Mobil 1 0W-40 European Formula (1,000 PPM ZDDP and a true synthetic) and when I started the car cold after the change, oil pressure was 50-60 PSI. I was using Mobil 1 15W-50 (1,200 PPM ZDDP) but I am about to change to AFR heads and Roller cam so I went with the light weight synthetic since ZDDP will no longer be an issue.
Check the oil sticky on the first page of the forum-Vette Magazine Article-March 2014 about oils for our cars, if your interested.
Check the oil sticky on the first page of the forum-Vette Magazine Article-March 2014 about oils for our cars, if your interested.
Last edited by jb78L-82; Feb 23, 2014 at 07:14 PM.
2026 Loser of the Year
Joined: Sep 2013
Posts: 36,595
Likes: 7,043
From: New Or-leens Loo-z-anna
350 SBC/60,000 miles
I have noticed that at idle the 10W-30 when new is
cold is 60 psi.........
warm is 45 psi....
185*F is 30 psi.....
195*F is 25 psi.
When the oil has 2,000 miles on it:
cold is 50 psi
warm is 35 psi
185*F is 25 psi
195*F is 16 psi
What is the normal operating temp of your engine?
I have noticed that at idle the 10W-30 when new is
cold is 60 psi.........
warm is 45 psi....
185*F is 30 psi.....
195*F is 25 psi.
When the oil has 2,000 miles on it:
cold is 50 psi
warm is 35 psi
185*F is 25 psi
195*F is 16 psi
What is the normal operating temp of your engine?
Last edited by doorgunner; Feb 24, 2014 at 12:29 AM.
Thread Starter
Le Mans Master
Joined: Jul 2006
Posts: 8,117
Likes: 104
From: charlotte north carolina
Thanks for the replies.
I've searched the web and found two items. One is oil leaking down past the distributor from an oil galley near the top and thereby reducing pressure-something I've never heard of or can understand. And two, a plugged or damaged oil filter allowing oil to pass thru the relief valve in the filter. I'll change the filter today and report back.
I've searched the web and found two items. One is oil leaking down past the distributor from an oil galley near the top and thereby reducing pressure-something I've never heard of or can understand. And two, a plugged or damaged oil filter allowing oil to pass thru the relief valve in the filter. I'll change the filter today and report back.
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Thread Starter
Le Mans Master
Joined: Jul 2006
Posts: 8,117
Likes: 104
From: charlotte north carolina
I changed the oil and filter without any improvement. I pulled the dissy and used my forementioned pump tool and got 30 pounds on two different gauges. I replaced the dissy and fired it up. I'm getting about 10 pounds when idling at 750 rpm. When I rev the engine to 1500 rpm, the pressure drops steadily and then rises again in a few seconds when I let it idle. It's got a stock oil pump and a four quart Summit G3510X oil pan. I'm starting to think that the pump is scavenging the oil too quickly (pick-up too high?) and the pump is starving for oil. As a test what harm could be done if I added an extra quart of oil? Anybody have any other thoughts?
Melting Slicks
Joined: Mar 2002
Posts: 2,164
Likes: 7
From: Beringen
Give us some details about the engine (bearing clearance etc). What type of oil pump, what of ancillaries ?
10-15 lbs is too low. Pressure is measured on the entrance to the block so at the end of the oil galleys it's even lower.
I've had oil pressure dropping on mine, but it only did it in the higher rpms. Still searching for a solution though.
10-15 lbs is too low. Pressure is measured on the entrance to the block so at the end of the oil galleys it's even lower.
I've had oil pressure dropping on mine, but it only did it in the higher rpms. Still searching for a solution though.
Safety Car
Joined: Nov 2008
Posts: 3,717
Likes: 551
From: Seattle Washington
I changed the oil and filter without any improvement. I pulled the dissy and used my forementioned pump tool and got 30 pounds on two different gauges. I replaced the dissy and fired it up. I'm getting about 10 pounds when idling at 750 rpm. When I rev the engine to 1500 rpm, the pressure drops steadily and then rises again in a few seconds when I let it idle. It's got a stock oil pump and a four quart Summit G3510X oil pan. I'm starting to think that the pump is scavenging the oil too quickly (pick-up too high?) and the pump is starving for oil. As a test what harm could be done if I added an extra quart of oil? Anybody have any other thoughts?
Drifting
Joined: Jun 2010
Posts: 1,781
Likes: 15
From: Oxford Ohio
Do you know what the bearing clearances were at the rods and mains, and rod to rod clearances at the rebuild? If it goes high when cold then the pump is working. Your clearances create the pressure. There is a max pressure control in the pump, but that seems to be working.
Thread Starter
Le Mans Master
Joined: Jul 2006
Posts: 8,117
Likes: 104
From: charlotte north carolina
Here's the problem
This mass of shreaded paper-like material completely covered the pump inlet screen. I dropped the pan and just touched it, and it plopped down into the pan that was sitting on the floor. I pulled the #1 cap (last one to get oil) and the bearing looked ok. I'm going to cut the old (actually it is a Fram filter that had about 2 hours of time on it) filter apart and see what it looks like inside.
This mass of shreaded paper-like material completely covered the pump inlet screen. I dropped the pan and just touched it, and it plopped down into the pan that was sitting on the floor. I pulled the #1 cap (last one to get oil) and the bearing looked ok. I'm going to cut the old (actually it is a Fram filter that had about 2 hours of time on it) filter apart and see what it looks like inside.
Burning Brakes
Joined: Dec 2008
Posts: 971
Likes: 45
From: Middlesex NJ
Man was that hiding in ur oil pan under the built in wind age tray?
Does it look like a rag or paper towel, easy to rip apart?
Sound like ur lucky and caught it early lucky lucky!
Had a similar issue on dodge dart my brother and I put a 383 in ... Rag was in the lower hose to keep antifreeze leaking out well it got jammed up inside we didn't see it and the pump shredded it and clogged the heads... Man did that stink.
Does it look like a rag or paper towel, easy to rip apart?
Sound like ur lucky and caught it early lucky lucky!
Had a similar issue on dodge dart my brother and I put a 383 in ... Rag was in the lower hose to keep antifreeze leaking out well it got jammed up inside we didn't see it and the pump shredded it and clogged the heads... Man did that stink.
Drifting
Joined: Jun 2013
Posts: 1,269
Likes: 226
From: Cocoa FL
Taken from this site: http://www.minimopar.net/oilfilters/opinions.html
http://www.minimopar.net/oilfilters/index.html
Years ago Fram was a quality filter manufacturer. Now their standard filter (the radioactive-orange cans) is one of the worst out there. It features cardboard end caps for the filter element that are glued in place. The rubber anti-drainback valve seals against the cardboard and frequently leaks, causing dirty oil to drain back into the pan. The bypass valves are plastic and are sometimes not molded correctly, which allows them to leak all the time. The stamped-metal threaded end is weakly constructed and it has smaller and fewer oil inlet holes, which may restrict flow. I had one of these filters fail in my previous car. The filter element collapsed and bits of filter and glue were circulating through my system. The oil passage to the head became blocked and the head got so hot from oil starvation that it actually melted the vacuum lines connected to it as well as the wires near it.
