Strange oil pressure problem
Thread Starter
Burning Brakes
Joined: Jun 2011
Posts: 816
Likes: 11
From: lewisburg wv
Strange oil pressure problem
This is a problem that was never resolved on a 77 Vette. When winding to 6000-6500 RPM's and suddenly decelerating the oil pressure would drop to zero for 1-2 seconds then come back up. If I would feather the throttle everything was ok. The engine was a LT-1 block, flat top pistons 292* Crane cam, single plane intake, 780 carb, double hump heads and headers. Engine was 355 CI. Had high volume oil pump and PCV connected. This has bugged be for years. Any thoughts are appreciated.
Le Mans Master
Joined: Mar 2004
Posts: 7,477
Likes: 1,495
From: Little Rock AR
Sounds like you could use better oil control. I would use a windage tray with a forward slosh baffle to prevent the oil from uncovering the pickup. You might also have the wrong pickup for the pan you are using. Corvette pans use a different specific pickup as compared to all the rest of the Chevy vehicle pickups.
Dr. Detroit
Joined: Mar 2012
Posts: 10,097
Likes: 4,027
From: New Braunfels Texas
The oil pan and pickup is specific for Vette's as mentioned.......the LT-1 has a Trap Door in the sump to keep oil from sloshing to the front during deceleration. The pan could be wrong, and the HV pump adds to the situation by moving more oil than is necessary to oil a small block. The pickup could be high too as mentioned......or all three things are happening....or possibly the trap door is stuck open/bent.
Pull the pan and inspect......and get rid of the HV pump....The HV pump was one of those old hold overs that will never go away......the pump moves more oil than the passages in the block have volume for.....and they run on bypass most of the time anyway.....the standard volume pump requires less horsepower to turn too and lessens wear and tear on the distributor gear, and related components.
As a side note....those old Cal Custom finned aluminum pans are the absolute worst.....they have a small "wall" cast into the front of the sump and not all the way across......they should really quit selling that thing......never ever use one.
Jebby
Pull the pan and inspect......and get rid of the HV pump....The HV pump was one of those old hold overs that will never go away......the pump moves more oil than the passages in the block have volume for.....and they run on bypass most of the time anyway.....the standard volume pump requires less horsepower to turn too and lessens wear and tear on the distributor gear, and related components.
As a side note....those old Cal Custom finned aluminum pans are the absolute worst.....they have a small "wall" cast into the front of the sump and not all the way across......they should really quit selling that thing......never ever use one.
Jebby
Last edited by Jebbysan; Jan 13, 2021 at 10:06 AM.
Le Mans Master
Joined: Aug 2017
Posts: 8,336
Likes: 2,810
From: Cool Northern Michigan
Before you start blaming the oil pan, oil pump, pickup tube, pickup screen and a host of other things:
You have a '77. You have an ELECTRIC oil press gauge. Its 44 yrs old.
The gauge receives its signal from a some-what reliable sending unit, with one of the most oily electrical connections on the entire car, by the oil filter.
Your issue only happens during decelleration, which is when the entire engine rocks back in its mounts.
Just speculating.
You have a '77. You have an ELECTRIC oil press gauge. Its 44 yrs old.
The gauge receives its signal from a some-what reliable sending unit, with one of the most oily electrical connections on the entire car, by the oil filter.
Your issue only happens during decelleration, which is when the entire engine rocks back in its mounts.
Just speculating.
Last edited by HeadsU.P.; Jan 13, 2021 at 07:02 PM.
