Prostreeter1

I changed the oil today on my 1968 408CI engine . The filter that was on it was a K&N HP-3002. The store didn't have that part number but they did have the K&N HP-3003 which I bought and installed with new Mobile 1 5w/30 oil.


I just found out looking at the K&N website that the HP-3002 does not have the filter bypass relief valve but the one I bought does.


Will this cause a problem with my engine?


Thanks guys!!

doorgunner

I think the bypass valve prevents oil starvation.....if the filter becomes clogged the bypass valve opens allowing the engine oil to keep circulating even though it won't be filtered.

68notray

The stock oil filter mount already has a built in bypass valve.

derekderek

If you change your oil every 50,000 miles, you need a bypass relief valve...

Prostreeter1

Thanks, guys. My conclusion is it wont hurt the engine. At cold start up its at 75PSI and hot idle 50PSI with both filters.

ddawson

Your fine, I don't have a bypass in my oil adapter housing so all oil is filtered.

Zero issues.

gkull

hey guys. The oil pump uses a spring and ball pressure limiting device. Once that pressure is exceeded it is bypassed , that means not going through the filter and right back into the pan

without a bypass you have to run higher pressure handling filters or they will burst like Wix and k&n

I have not studied bypass filters to see exactly what they are doing

all performance motors need to block the bypass channel in the block

C6_Racer_X

To answer the question posed in the opening post, it doesn't hurt anything to have two filter bypass valves, one in the engine, one in the filter itself.



It's generally a bad idea to have zero bypass valves, like installing a filter without a bypass valve on an engine that doesn't have a bypass valve in it and is designed to use a filter that includes the bypass valve.



You're getting two separate devices conflated.

The pressure limiting valve at the oil pump is to limit the system pressure to a maximum value, no matter the engine speed or operating conditions (temperature, etc.). That usually dumps right back in the pan. That's usually set to a fairly high pressure, to keep pressure in the bearings, but to protect the oil filter from bursting under excessive pressure.

The bypass valve can either be in the filter itself or in (or near) the filter adapter on the engine. The purpose of the filter bypass valve is to provide a path for oil in the event the filter is restrictive. The filter bypass valve is sensitive to the pressure difference between the filter inlet and the filter outlet passages. It's generally set to a fairly low pressure to open (12psi to 20psi is common). The bypass valve connects between the inlet and the outlet of the oil filter. If it's in the filter itself, it's at the top and allows flow through the top of the filter. If it's in the filter bracket or block, it connects between the inlet and outlet passages to the filter.

There are two reasons the bypass valve will open. One is maintenance issue, the other is a design issue.

If the oil filter is clogged with dirt and debris, the bypass valve can open to allow oil to flow around the clogged filter. The thinking is, dirty oil to the bearings is still better than no oil to the bearings. That's a maintenance issue. If you change your oil and filter at proper intervals, this should not occur.

The other issue that can open a filter bypass valve is if the flow of oil from the oil pump exceeds the flow capacity of the filtration media. When that happens, the filter becomes a restriction, and pressure at the filter outlet (and into the bearings) can fall. When the pressure drop across the filter exceeds the bypass valve setting, the valve opens and allows unfiltered oil to go around the filter. Again, this is better than no oil or a lower volume of oil at very low pressure. This is a design flaw, but it's not uncommon. LS2 engines in C6 Corvettes have this by design. The AC-Delco PF46E filters commonly used on those engines are rated for about 3GPM. The stock oil pump is capable of pumping close to 7GPM at high RPMs. Over about 3500 RPMs, with the AC-Delco filter, the filter bypass valve starts to open to allow more oil flow.

If you have that design flaw, selecting another after market oil filter with higher flow capacity is a really good idea™.

stingr69

The oil pump has a pressure regulating valve that bypasses directly back to the pan to regulate oil system pressure but that is not a concern here. We are worried just about the loss in oil pressure between the inlet and outlet of the filter.

No problems that come to mind for your situation. If it was a fresh build on an old style flat tappet engine it might worry me a bit. The molly paste assembly lube will all end up in the filter during break-in. The filter can get clogged up enough to allow a bypass (filter bypass or filter mount bypass) to open and that would be the worst time for it. Fresh builds have lots of bad crud in the oil so you always change oil and filter right after. You do not want any internal filter bypass or filter mount bypass during break-in.

Gen 1 Filter mount bypass is easy to disable. You can remove the mount with the 2 screws and pop out the bypass washer/spring then tap the opening for a 1/4 pipe plug. done.

derekderek

Got a free dodge dart with slant six. Shimmed the oil pump spring. On startup, oil psi guage hit the pin and filter exploded, in 2 seconds...