The Stovebolt Site Forums The Shop Area Engine Shop is it normal for oil to drain from filter line overnight

I am installing a 261 in my 46 chevy 3/4 ton. I got the short block. When I went to prime the oil pump I put some clear hose as a temp setup between the input and return lines for the oil pump.
Everything primed OK, but I noticed that the oil drained out of the clear line overnight.
I did not think much about it and worked on he body, ....

Several months later it is time to crank up the motor for the first time. I install a remote oil filter, I have a fram oil filter with check valve built in to it. Decided to crank until I had oil presure. So with the spark plugs out start cranking, and cranking, and cranking. ..... finally got oil pressure.

Now I crank the engine to get oil presure before I turn on the ignition. If it sits overnioght, it takes a long time, and I know that that is to get it to the remote filter..

I saw in the manual that it was important to seal the oil pump from air leaks. The oil pump was in from the short block. I am not sure where to seal it.

Is this normal?

If you are running a remote full pressure oil filter where the engint oil pump is connected with a flexable pipe to the remote filter and then back to the engine block it is important to have the filter and associated flexable lines as much paralled as possible to the oil pan. If the filter is mounted on the fire wall you will get drain back and more air in the system.

I do have the remote mounted up on the firewall.
But I had the problem when I had just a 12 inch piece of tubing connecting the input and output.

I thought that the original oil filter was bolted to the intake manifold and was alos up pretty high.

It is. But since I don't have clear lines I don't have a problem.

You can get an oil filter with an anti-drainback valve. Keeps the oil in the filter from draining back to the pump.

I have an antidrain in the filter, but the line still drains. The filter is full but not the line.

The oil filter is a partial flow on these engines? In that one the extra oil not able to go through the engine oiling is forced to the filter.The oil doesn't com directly off the oil pump but from a passage in the block and returns to the oil pan.

I have expereinced the same situation....

BUT... I was pretty darn sure that the 261 has a full flow oil system.... in fact if you plugged the outlet and inlet with pipe plugs and fire up the engine you would have no oil circulation....

....so I have read and not about to test out on my new 261...... any comments from real experts as I am not.....

My dual filters are installed even/level with the clear HD oil lines going out of the block and attached to the testing frame using about 36 inches of heavy clear lines. Since I did not fire up the engine before Winter I mothballed the 261 by running up the pressure with a 3/8 HD electric drill..... got the oil pressure up to 42 pounds on a mechanical gauge....all the while spinning the engine with the starter w/o plugs.... one line blew off as I had not installed any hose clamps not thinking that the cold oil could develop that much pressure.

Now for the clincher.... within an hour oil had drained back into the block... repeated the process twice... after installing hose clamps and refilling the engine...same results... I am sure the filters are still full...BUT the lines have air both sides of the filters.

How critical is this situation???? would I have the problem if I used opaque lines... no see no worry????

The Original GM filter was a long canister held to the intake manifold...fairly high above the oil pan.... some military model similar to mine had the oil filter canister mounted sideways on the frame... somewhat lower than the edge of the oil pan.....

So what is the best location... high or low...??

....and Jason.... what brand of filter have the anti flowback valve.... my remote is set up for standard PH 8 long spin on filters...common on Chryslers and some older Fords.....

Thanks for you help..