Funny you should mention this. I just built a 'new' 4-bolt main 350, which
I stroked and bored to get 383ci. I almost had a 'BIG ONE' when I fired it
up and had what appeared to be 0 (ZERO) oil pressure. I shut it down and
checked all my notes. I too had good to minimum readings on my plasti-
gauge. I was running 10-40w oil and a new 'high volume' oil pump. I had
even primed the engine before I had lowered it into the truck. STUMPED?!
In desperation after all my checks I put a seasoned Melling High Volume/
High Pressure pump in and fired it again. This one had performed with
excellent results on the previous engine. The pressure was STILL hovering
around the zero mark. Now I was REALLY worried and concerned for my
heavy investment in crank, pistons,rods,etc!
I worked on it into the morning. (The wife was upset.) I had probed
I could reach. I couldn't find anything which make sense. I purchased a
genuine GM Corvette High Volume/High Pressure pump. (Cachingggg! The sound
of dollars racing out of my account?) I installed the new pump. I used a
and again looked into every area of the top and bottom of the engine I could
removing pans, etc.
Then while getting ready to put the lower pan on I noticed it had a small
metal in the bottom. It had apparently fallen from the engine to the oil
then into the pan. I did some more searching and fount two other smaller
of waded up metal.
Apparently these "doer's of damage" had been wedged in one of the oil
between the pump and the pressure gauge tap. Horrors! I had missed them. I
no place in or around the engine which was missing any metal. I can only
that they had been in the engine when I received it from the machine shop. I
the machine shop guys. They would not have allowed this if they had known
about. We had all missed the trapped bits of metal.
I am still using the Corvette pump. When cold I get 40lbs of pressure.
and idling I get about 5-6lbs of pressure. This is still alarming but I
these are the same readings as documented in the tech book for the
I expect to pull the oil pan and do some more probing with a tiny magnet on
telescoping rod. I believe there may still be some foreign matter trapped.
PS My good Melling pump did 40lbs when hot and idle and 60lbs when hot
and off idle. This is good except it is such a high pressure it seems
find ANY small opportunity to leak.
----- Original Message -----
From: Terry Stellman <STELLMAN@noex.com>
To: Truck List (E-mail) <firstname.lastname@example.org>
Sent: Tuesday, January 18, 2000 8:52 AM
Subject: [oletrucks] Oil Pressure Problems?
> I need some expert advice. I have a 350 4 bolt main that I personally
> rebuilt and installed in my truck. When I start it ,it has 60# + of oil
> pressure but when I drive it a few miles (4-5) and stop at a red light or
> something the oil pressure will drop to 0-10# when idling. As soon as I
> accelerate it will shoot up to 40# and settle back to 25-30# when cruising
> down the highway at 2000 rpm. It had a brand new Melling standard oil
> that I have already replaced with another Melling standard oil pump. I
> never used one of these before. In the past I have always used Chevy oil
> pumps and don't remember ever seeing this much pressure fluctuation and
> those low of readings. Does anybody have any ideas what could be wrong?
> this normal for Melling oil pumps? Should I replace it with a Chevy pump?
> Could there be some other problem? I Plasticgaged the bearings when I
> assembled it and everything was on the minimum side of the tolerances.
> I am running 10W40 oil. Any help or suggestions would be appreciated. I
> really am not looking forward to taking the engine out and completely
> rebuilding it again just to try and find this problem. TIA>
> Terry Stellman
> 1949 3600
> Missouri City, Texas
> oletrucks is devoted to Chevy and GM trucks built between 1941 and 1959
oletrucks is devoted to Chevy and GM trucks built between 1941 and 1959