Last winter I built a 540 Dart BBC motor as described in my signature. I have a Hardine Marine 10 quart racing oil pan (p/n 260-9105) and a CP performance blueprinted HV BBC oil pump (p/n 250-OP-BB-B) with the Hardine Marine supplied Morosso oil pump pickup (p/n 710-24290). I do not have the standard oil flow setup that is external to the motor. I have a large capacity oil cooler and a transom mounted oil filter with a K&N reuseable oil filter.

Here is what happens. Start the motor and I have a solid 80psi oil pressure. When motor gets to operating temp and I'm cruising at about 1800 RPM, oil pressure drops gradually to approximately 60psi. I'm running Royal Purple 20W-50 oil. As I accelerate to 2200 RPM the oil pressure drops to 40psi. When I accelerate to get on plane, the oil pressure drops gradually to betweens 0 and 20 psi. I pull back on the throttle and at 3200 RPM I have about 5 psi of oil pressure. Can't go any further or it drops to 0. I have a mechanical oil pressure gauge mount on the oil filter bracket. It reads the same as the electric dash gauge. So I know it is not a guage issue. I rock the boat back and forth and even went into a hard turn. Oil pressure does not vary at all. Pull the throttle back to 2200 RPM and have a rock solid 40 psi.

Here is what I did. I thought the oil pump was starving for oil. As the RPM increased, the oil pressure dropped. So I pulled the motor and checked the clearance between the pan and the Moroso pickup. Approximately 1/4". Called Melling and talked with one of there techs. He said the pickup to pan clearance shaould be approximately 3/8" to 1/2". So I ordered the Melling pickup, installed it and verified the correct clearance. Took the boat out Friday and had the same issue with the Melling pickup as I did with the Moroso. pickup. So now I'm not sure what the problem is. I'm leaning towards a bad oil pump with a possible broken pressure regulator spring.

Any help would be appreciated or suggestions on who to talk to about this issue.

Ed
'99 Sonic Prowler 260
540 CNC Motorsports Racing Short Block/9:1 CR
Dart PRO-1 Aluminum Heads/SS Intakes/Inconel Exhausts
Cometic SS Head Gaskets
IMCO Aluminum Exhaust/Hardine Polished SS Risers/SS Gaskets
Comp Roller Cam: .547/.547 Lift – 230°/236° Duration – 112° Overlap
Comp Roller Lifters/ Roller Rockers/Push Rods (.375")
ARP Main &Head Studs/Rod Bolts
Hardine 10 Quart Marine Racing Oil Pan
High Capacity Oil Cooler
Remote Oil Filter (Transom)/K&N Reusable SS Oil Filter
Complete MSD Ignition/Cooling Fan
Denso Iridium Plugs/MSD Plug Wires
TPiS 68mm Throttle Body
K&N/Hardine Marine/PWR Air Intake Filtration
ECM Upgrade to 525 Tune
San Juan FWC
RACOR Fuel/Water Separator
Aeromotor EFI Fuel Pump/Regulator
Aeroquip Stainless Steel Fuel Lines

It sounds to me like you're pushing past the regulator spring. I've seen this before.

When you pulled the pan back off did you check the bearings? Also, were the clearances measured on assembly? If that checks out double check your oil cooler line routing to make sure things aren't backwards and also make sure you are running a 30 lb. bypass valve in the block, not the 11 lb. valve that is used in the automotive motors.

This is an old thread from last year. So what was the issue that was causing this low Oil Pressure?

When I installed the Moroso oil pump pickup, I cut off the install tab like the directions stated. However, I put a small hole in the pickup tube with the hacksaw and was not aware of it. At plane and around 3300 RPM I started loosing oil pressure that eventually went almost to 0 before I went to idle. At idle I had about 20 psi. Pulled the motor and installed a Mellon oil pump pickup. Bad move. No way to attach to oil pump but was told with confidence that it would work. I knew better but I did it anyway. No joy! When I pulled the motor last week, found the Mellon pickup in the oil pan with some hurt marks on it. No damage to my oil pan. So I installed a new Moroso pickup. I put the pickup in the vice and drove the pump on the pickup vice the other way. I left the pickup tab on this time. Took it out last Friday and I have 30 to 40 psi at 4200 RPM. Problem solved. Have not gone WOT as I'm still breaking in the motor.

Ed

Thanks for the update

Did you check the bearings when the pan was off? 30-40psi at 4200 RPM seems kind of low to me. What pump is installed in this motor? I would be concerned you scored up some bearings from oil starvation.

+1

+ 2 ! Actually + 3. Lol.

No I did not check the bearings since the obvious problem was the oil pump pickup. The oil pump is a CP Performance BBC high volume blue printed pump part # 250-OP-BB-B. As you can see from my OP sig, I have a large 10 quart flat bottom dual trap door racing oil pan and not the standard oil pan where all of the oil is in the back of the pan. So static pump suction pressure is less. I have a 3" X 16" CPP oil cooler, part# 620-550, and a remote located K&N re-useable SS oil filter mounted on the transom. There are four 30" oil hoses that connect the oil cooler and filter to the motor. So my oil system has virtually no back pressure other then the motor. My oil temperature runs approximately 190°F. If I have a bearing issue, I would think it would be obvious from idle to my max RPM so far of 4500. The motor is still going through break-in and I'm varying the RPM from about 3,000 to 4,500. I only have 3.3 hours of actual run time on it.

Ed