The Stovebolt Site Forums The Shop Area General Truck Talk Low Oil Pressure with Add-On oil filter.

Hi-
Does any body know if an Add-On oil filter will affect oil pressure readings? I have a 1957 Chevy in line six. The oil pressure line and the large oil filter line share a single opening
at bottom of block. My pressure gauge is reading zero. Copper lines and gauge are clear.
When I disconnect copper line from gauge and run engine: no oil at end of pipe at all.
When I open connector at block, oil drains out steady but slow with engine running.
Tnx for any info.
Ron A
Colonie, NY

It will not effect the oil pressure. I added one to my original 1954 235 that had never had an oil filter and there was zero impact on the oil pressure., All the oil does not flow through the oil filter. I forget the term but I think it is bypass filter.

Depends on the motor and the filter. If you have a real 57 235 block, then that motor uses a bypass filter. Notice the id of the oil feed lines, small. So what happens is that the bypass style filter bleeds a little oil from the mains, filters it, and then dumps it back into the pan where it is immediately diluted by dirty oil. Now, using the bypass filter will not bleed enough pressure to lower the over all pressure to the motor in any noticeable amount.

Now, install a remote spin on filter and use the largest id lines you can find. Now you are bleeding way to much oil pressure from the mains and you will lower the oil pressure in a noticeable amount.

Stock bypass filter, use the correct size lines, you are all set. Aftermarket spin on filter, yes you can use it, just make sure there is restriction the size of the id of the stock lines somewhere in the return, either by using a small id line, or some have used soldered and drilled fittings, and you are all set.

That being said, if you have a later model 261 motor that is set up for full flow oil filtration, then you can use the after market spin on with the appropriate full flow hoses.

The original style bypass filter has the restriction made into the inlet port, remove cover and see, should be no larger than 0.0625” or 1/16”.
Regardless of the line size used for a bypass filter you need to be sure there is the proper restriction either as part of the filter or a separate restricted fitting. The smaller line size alone is not adequate.

If you’ve put on a modern spin on filter head to use as a bypass filter then find a filter intended for use as a bypass (usually filters finer than full flow) they may have a restriction built inside the filter depending on model. Still it’d be safe to add a 1/16” restricted fitting to the inlet.

Outlet of a bypass filter drains right into the sump, usually near the pan rail.

I added a picture above.

Is the distributor seated and driving the oil pump?

The pump has an internal pressure relief valve, small chance the spring is broken or trash stuck in the seat holding it open.

You should have pressure from that port for the gauge with engine running.

It is hard to tell from your picture but it looks like you might have your lines backwards. The T fitting needs to go to your oil pressure gauge and the line going to top side fitting of the oil filter canister. The return line from the bottom of the oil filter canister goes directly to the fitting in the block.

If you opened the T at the block and the oil with the engine running ran out slowly, you have a big problem. Normally that would make a huge mess in seconds.

Figure out why you don't have oil pressure WITHOUT the filter. You're obsessing about a minor annoyance like a sore thumb while you're in the middle of a heart attack!
Jerry

I put one on my 1954 235 and yes the gauge read zero, so I have been running without a filter for the last 10 years. I have posted about it and Hot Rod Lincoln has a definitive answer to correct the reading. Unfortunately, I do not have the skills to do the job. I have thought about putting the old cannister back on.

This ads like my situation. I'm gonna remove oil cannister.
I have two ports to choose from to attach pressure gauge pipe;
I'll probably use the one further back on block.
Tnx.

One port on left side of block is coolant drain...

I removed the filter on my 57 235 and the oil pressure went up so there is something wrong with the filter,I am going to change the oil more frequently.

If removing or disabling the normal type of original bypass filter such as a Fram or AC raises the oil pressure noticeably, something else is seriously wrong with the lubricating system, either badly worn bearings, or possibly a stuck oil pump relief valve. The amount of oil that can flow through the 1/16" diameter flow control hole in the filter standpipe cannot possibly have much of an effect on a healthy oil system.
Jerry