Keith: 3/9/2000 - 5:18:22 PM
Low Oil Pressure
I'm concerned about the oil pressure on my freshly rebuilt 8BA. Cold, it runs about 30 psi at both idle and crusing speed. After a long run (normal engine temp), the pressure falls to near zero at idle, but will increase to 30 psi at 1500 RPM. I personally checked all bearing clearances when the engine was assembled, and there isn't any noise in the engine; it's got about 1,000 miles on it since the rebuild. I recall reading that the sludge trap soft plugs occassionally come out (I replaced them and they fit tight). Before I pull the pan, I was hoping for some expert advice.

Harlan: 3/9/2000 - 6:45:10 PM
RE: Low Oil Pressure
What did you use for an oil pump. Thit is about what an origenal early oil pump would put out. If you are not runing a blower you dont need high volume or high presser. What bloch are you using. Is it a 59 with the oil relefe in the valve gally and did the spring and plunger get reinstaled at rebuild time.

JWL: 3/9/2000 - 7:27:39 PM
RE: Low Oil Pressure
Is this a new problem or has the behavior of the oil pressure been as described since the inception of the rebuild? If you have the helical gear pump, and everything is ''right'' the pressure is usually about double your readings. Are you certain about the accuracy of the guage? If this is a new problem, it might be a loose relief valve or contamination in the valve, or a broken spring. It might also be a loose pickup tube. If this is a problem which has persisted basically since the rebuild I wonder if you have an undersize cam running in std. bearings? Most builders don't measure these. More information would be helpful.

Keith: 3/9/2000 - 11:55:12 PM
RE: Low Oil Pressure
I don't know if the pump has helical gears; I bought a rebuild kit from Patricks in Arizona. The cam is new (Isky MAX1). I didn't mike the journals on the cam, I assumed it was standard. I did mike the crank, and plastigauged all bearings. The oil pressure has been checked with another known good gauge. Do you know of any way to check cam bearing clearance without removing the camshaft?

flatjack: 3/9/2000 - 7:38:08 PM
RE: Low Oil Pressure
I would definetly check the pressure with a good direct reading gauge before tearing anything down.

Billk: 3/9/2000 - 8:49:03 PM
RE: Low Oil Pressure
I agree that it might be the cam journals worn. Remember that the oil goes to the cam bearings first, then to the mains. If the cam bearings have too much clearance, the pressure is lost at this point. You might be able to pick up some pressure by switching to the new Mellings M15 high volume pump. It has longer gears and pushes more oil to make up for loose clearances.

trader: 3/9/2000 - 10:27:28 PM
RE: Low Oil Pressure
Does the motor have a parasitic oil filter? Did you install the galley plug behind the cam gear? How about fuel pump push rod bushing?

JWL: 3/9/2000 - 10:37:26 PM
RE: Low Oil Pressure
He said it was 8BA. The pushrod bushing would not be involved.

Keith: 3/9/2000 - 11:57:58 PM
RE: Low Oil Pressure
I've got a stock oil filter, and did install the oil galley plug. I don't think the pushrod bushing has any effect on oil pressure in an 8BA.

finn34: 3/10/2000 - 1:30:56 AM
RE: Low Oil Pressure
Does the 8ba have a relief valve in the valve galley (have 59 myself, so I do not remember). If it has check the spring. 30 when cold at high rpms indicates that a relief valve is opening.

JWL: 3/10/2000 - 7:00:37 AM
RE: Low Oil Pressure
Start with the oil pump. If no problem is found, and it is the correct, helical gear, short body pump, then look inside the engine. The 30 lbs. cold cruise and cold idle really indicates a relief valve problem.

Walt Dupont: 3/10/2000 - 6:07:13 PM
RE: Low Oil Pressure
Keith. you've had a lot of replys so i'll give you my two cents worth. It sounds to me like a bad pressure relief valve or spring, make sure you got the helical gear pump.I have a oil pressure tank that i made from a freon bottle. In the 45 yr's i've been building engines, i've found a lot of oil pressure problems with it. With the pan off, pump oil into the main oil line, look up an see if there is an excessive amount of oil leaking around the cam brg. You said you plastic gauge the rods and mains so they sould be all right. My money is on the oil pump. Walt

rumble seat: 3/10/2000 - 10:01:46 AM
RE: Low Oil Pressure
Keith: If a sludge trap plug came loose, you'd know it. They knock REALLY loud! (Sounds like the rod bearings are non-existant.) 8BA's don't have a fuel pump pushrod bushing nor a relief valve in the front of the block like a 59AB engine. I'd start with the oil pump since it sounds to me like the oil pump relief valve is sticking open or the spring is weak. I'm assuming you've got a short bodied pump with a relief valve, helical cut gears, and correct pick up. Pull the relief spring and valve. Clean the seat and valve really good. Then stretch the spring about 3/8 inch or add 0.100 inch or so of washer. I know lots of guys here are going to say to not do this for various reasons, but I'm a believer in stretching and/or shimming springs big time. I even do it to new and NOS pumps. rumble seat

32tom: 3/10/2000 - 9:32:37 PM
RE: Low Oil Pressure
Is there a brand name for the helical gear pump? any recomendations?

Jim Marlett: : 3/11/2000 - 8:16:43 AM
RE: Low Oil Pressure
The Melling replacement pumps sold by virtually all flathead suppliers is the short body pump with helical gears. 1950 was when Ford started using helical gear pumps.

rumble seat: 3/10/2000 - 10:12:46 AM
Don't have your E-mail or I'd have written you direct and not tied up this forum. In your reply to Keith on oil pressure on 3/9, you stated a couple of things that I have a couple of questions on. 1)You state oil pressure is usually double the readings when using a helical pump. Please explain how changing an oil pump can affect an oil pressure gauge, either an electric or mechanical. 2)You state the low oil pressure could be caused by a loose pickup tube. I'm assuming you're thinking the break is above the oil level line and the pump is having air introduced into the pump. Is this your thinking? I appreciate you taking the time to answer me since I value your expertise very highly.

JWL: 3/10/2000 - 11:47:54 AM
My response refered to his readings of 30 lbs. Usually the helical pump will supply between 55 and 60 lbs. in a tight engine. (double his readings) Yes, I saw one example where the low oil pressure problem was traced to the pickup being loose. The short body pumps I use are about 4 5/16'' from mounting flange to outside of gear cover and over 7'' to bottom of pickup.

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