Bypass Oil Filter questions and thoughts

[38Plyroadking]

I've been thinking about this a lot lately since I had an issue with the oil pressure gage on my 38 coupe reading 0 upon start up, and continuing to read 0 for another 40 minutes of running at which time it rose to a whopping 8 PSI. Fixed that by putting a spacer behind the tired bypass valve spring (I know, I should buy a new spring, but I am impatient. ). I knew the spring was probably the problem from reading all of the good info here on this site. Thanks.

Anyway, I was wondering about a couple of things.

1. The valve, by design, allows oil to flow through the filter when pressure is sufficient...Is this correct.....What is that pressure?

2. If you put the stiffer spring in to increase the pressure would that mean that more oil would flow through the filter?

2. Is it possible to convert this to a full time filtering system?

Paul

[Joe Flanagan]

The relief valve controls the flow of oil from the filter back to the block. When you're cranking the engine, oil is being pumped up to the canister but it can't actually re-enter the engine until the oil pressure overcomes the spring and opens the relief valve. That is how I understand it from reading the manual and looking at the diagram that shows how the system operates. When I first started my rebuilt engine (the first rebuild, don't ask), my relief valve was stuck and the maximum pressure I could get was 10 lbs. Once I freed it, all was good.

[38Plyroadking]

Correct, agreed. But at what pressure? It seems to me that you'd get more filtering on a cold engine than a warm one. Does that sound logical? So, if we increase the pressure during the warm "phase" of operating the engine (using a heavier spring) then we could increase the lenght of time the oil flows through the filter. I assume that the integrity of the filter can has to be maintained to withstand that pressure also.

Just trying to think logically here, sort of out of the box. Then there is my second second question (just noticed that typo there, really the third q) of if it can be converted to a full time system.

Paul

[1941Rick]

Looking at my drawings I see the oil coming from the pump to a common oil gallery. the relief valve then controls the max pressure in the engine. when excess pressure is sensed the valve opens and dumps the oil back to the base. The bypass filter takes oil from the oil gallery and returns the oil back to the base behind the relief valve. Increasing the spring tension will only have an effect on Max pressure. If you have low pressure you may have a faulty (leaking) relief valve, a stuck open relief valve, a weak oil pump, or a bearing problem furthur along the engine.

As for making a full flow system on the engine , I have read where modifications are made right at the oil pump. The base where the pump mounts is drilled and oil is diverted thru a full flow filter before entering the engine. On these engines I feel the by-pass is sufficient.

[Plymouthy Adams]

at engine idle the oil pressure is low...nothing goes to the filter and nothing is returned back to the oil pan through the excess oil bercause the relief valve is covering the outlet ...once it hits about 10 lbs the filter discharge is opened and is wide open at 40-45 lbs of pressure

[greg g]

The rate of flow through the filter is aproximatly 30% of volume. If the filter clogs, the flow bypasses the filter thereby assuring flow to the engine, which is the more improtant path. While the 30% may seem like a lot of filtering, it actually only take a few minutes of running to pass the 5.5 quarts through the system.

Keep in mind that alot of these engines ran for years with no filter at all.