Oil flow - filter by pass - 427 PF141

[Ronald L.]

How do you know if the oil is passing through the original canister style filter?

Is there a way to verify the oil flow routing, that is how it enters that its not skating past via a bad relief valve, etc?

[Clem Z.]

Re: Oil flow - filter by pass - 427 PF141

How do you know if the oil is passing through the original canister style filter?

Is there a way to verify the oil flow routing, that is how it enters that its not skating past via a bad relief valve, etc?

feel the canister to see if it is hot or better yet use a IR gun to see if the pan and the filter are the same temp. if the by pass valve micarta disk and spring are in place it should work

[Joe L.]

Re: Oil flow - filter by pass - 427 PF141

if the by pass valve micarta disk and spring are in place it should work

clem-----


Yes, these things are not exactly a "high tech" sort of contraption. They're about as simple as anything could be.

[Ken A.]

Re: Oil flow - filter by pass - 427 PF141

You don't, unless you eliminate the bypass. It is only there for people who never change oil & the filter stops up. Highly unlikely in our cars but possible if the engine fails-then it is a moot point.

[Clem Z.]

Re: Oil flow - filter by pass - 427 PF141

You don't, unless you eliminate the bypass. It is only there for people who never change oil & the filter stops up. Highly unlikely in our cars but possible if the engine fails-then it is a moot point.

you can tell by the oil pressure gauge if the bypass is blocked. if the bypass is blocked the oil pressure comes up slowly as the oil work its way thru the filter. with the by pass working the pressure will jump right up because the unfiltered oil is bypassing the filter till the oil pressure equalizes on both sides of the bypass valve disk causing it to close

[Michael H.]

Re: Oil flow - filter by pass - 427 PF141

you can tell by the oil pressure gauge if the bypass is blocked. if the bypass is blocked the oil pressure comes up slowly as the oil work its way thru the filter. with the by pass working the pressure will jump right up because the unfiltered oil is bypassing the filter till the oil pressure equalizes on both sides of the bypass valve disk causing it to close

Clem,

The valve is normally closed. It's closed at start up too, even if the filter is empty.

[Clem Z.]

Re: Oil flow - filter by pass - 427 PF141

Clem,

The valve is normally closed. It's closed at start up too, even if the filter is empty.

when the filter is full the valve blows open because of the restriction of the filter as the oil takes the path of least resistance thru the valve till oil fill the oil passages in the engine to create a back pressure on the valve. the rear main always show scratches from dirty oil getting thru before the by pass valve closes. this may only takes seconds but it happens. i noticed this on race engines with and without the valve blocked as you can see it on the pressure gauge. blocked the pressure come up slowly and valve working the pressure shoot up right away. the first time i blocked the bypass valve and started the engine it took me by surprise that the oil pressure came up so slowly as i thought something was wrong with the engine.

[Michael H.]

Re: Oil flow - filter by pass - 427 PF141

when the filter is full the valve blows open because of the restriction of the filter as the oil takes the path of least resistance thru the valve till oil fill the oil passages in the engine to create a back pressure on the valve. the rear main always show scratches from dirty oil getting thru before the by pass valve closes. this may only takes seconds but it happens. i noticed this on race engines with and without the valve blocked as you can see it on the pressure gauge. blocked the pressure come up slowly and valve working the pressure shoot up right away. the first time i blocked the bypass valve and started the engine it took me by surprise that the oil pressure came up so slowly as i thought something was wrong with the engine.

If you start an engine with an empty oil filter canister, the oil flow has two choices. Go through the filter or force the bypass valve open and bypass the filter. Since it takes very little pressure to direct oil through an empty filter, but it takes somewhere around 11 PSI to open the bypass valve to bypass the filter, the most likely path the oil will take is through the filter.
The bypass valve opens if the filter is restricted.

[Clem Z.]

Re: Oil flow - filter by pass - 427 PF141

If you start an engine with an empty oil filter canister, the oil flow has two choices. Go through the filter or force the bypass valve open and bypass the filter. Since it takes very little pressure to direct oil through an empty filter, but it takes somewhere around 11 PSI to open the bypass valve to bypass the filter, the most likely path the oil will take is through the filter.
The bypass valve opens if the filter is restricted.

when the filter is full of cold oil it is a restriction to the rest of the open oil system and with no oil pressure in the rest of the engine the valve will open till the oil pressure equalizes in the system.

[Ronald L.]

Re: Oil flow - filter by pass - 427 PF141

I knew I was stepping into a good one

Let's see what happens tomorrow, ie the pan and filter can are about as hot after I get it out and break the three digit mph, oh ya.

I sense some of oil pressure slow creep up is there, but can't speculate why.

[Ken A.]

Re: Oil flow - filter by pass - 427 PF141

you can tell by the oil pressure gauge if the bypass is blocked. if the bypass is blocked the oil pressure comes up slowly as the oil work its way thru the filter. with the by pass working the pressure will jump right up because the unfiltered oil is bypassing the filter till the oil pressure equalizes on both sides of the bypass valve disk causing it to close

I've never seen this happen in 40 years of running Chevys with a blocked bupass. Oil pressure is instantaneous at startup, unless the car has been sitting a week or more. The bearings, on teardown inspection, always looked like good to new.

[Clem Z.]

Re: Oil flow - filter by pass - 427 PF141

I've never seen this happen in 40 years of running Chevys with a blocked bupass. Oil pressure is instantaneous at startup, unless the car has been sitting a week or more. The bearings, on teardown inspection, always looked like good to new.

race car engines usually set a week or longer between races and the oil drains out of the galleries. with a by pass valve is where you see scratches in the rear main inserts because dirty unfiltered oil get to the rear main first till the by pass closes. repeated startups you do not see the slow build up of pressure as the galleries are still full of oil. my point was this is how you can tell if the by pass is blocked on the first start up.

[Ken A.]

Re: Oil flow - filter by pass - 427 PF141

race car engines usually set a week or longer between races and the oil drains out of the galleries. with a by pass valve is where you see scratches in the rear main inserts because dirty unfiltered oil get to the rear main first till the by pass closes. repeated startups you do not see the slow build up of pressure as the galleries are still full of oil. my point was this is how you can tell if the by pass is blocked on the first start up.

I still do not understand your reasoning. The reason to block the bypass is to force the oil to be pumped thru the filter-thus eliminating "dirty unfiltered oil" & bearing damage. The gauge pickup point on most GM race or mild street engines is right above the filter. After a week of sitting, a few spins on the starter produces instant oil pressure. Of course you were using an Accusump on your race motors, right?

[Clem Z.]

Re: Oil flow - filter by pass - 427 PF141

I still do not understand your reasoning. The reason to block the bypass is to force the oil to be pumped thru the filter-thus eliminating "dirty unfiltered oil" & bearing damage. The gauge pickup point on most GM race or mild street engines is right above the filter. After a week of sitting, a few spins on the starter produces instant oil pressure. Of course you were using an Accusump on your race motors, right?

never use a accusump and never lost a engine from oiling problems. always ran road race pans even on my circle track engines because of spin outs can cause oil to run away from the pickup on left turn type pans. ran dry sumps were they were allowed. all i am saying is it take a few seconds for the cold oil to move thru the filter and fill the oil galleries so the pressure will come up slowly in stead of jumping to full pressure on the gauge. you may not see this if you used the standard 1/8" dia oil pressure line but i always used 1/4' line to get faster reaction to the pressure changes. you don't see pressure on the gauge till the whole system is full of oil since what you are seeing is resistance to flow to build the pressure.

[Clem Z.]

Re: Oil flow - filter by pass - 427 PF141

back in the day when GM quit selling aluminum BB and smitty at yenko had not yet gotten theirs made i used a block supplied by the customer that was cast by dove engineering in ohio. against my better judgement i built a circle track 454 engine. the first night the oil pressure went from 70# to about 40# at the end of the races because the coolant was getting into the oil because the block was so porous and the water was swelling the paper media in the filter causing the holes to close up and the flow was restricted so the pressure was dropping. if i had not blocked the filter bypass we may have never caught the problem till it was too late and the engine was ruined. i called my contact at GM about my problem and they had just came out with the PF 35L which had a synthetic media that did not swell in water. this solved the oil pressure problem but they still had to drain the water from the oil after every race. the engine ran this way for years without any damage.