RU7376vettes

I assembled this engine about 10 years ago when I restored my 73 L-82 with modifications. On Sunday going to a cruise in the oil pressure dropped from around 60 down to ~25 whenever I got over 3500 RPM. Mechanical gage and at all other times it seems to be reading fine. Has High Volume Oil Pump and a 7 quart oil pan. Engine is bored .030 with 1/8" domed pistons and Comp 268 cam. Oil is Shell Rotella. Filter is Delco PF-1218 (long version of PF-454). Engine has about 10,000 miles on it since I put it together. Just got the car out again after 3 months of sitting. Changed oil and filter this spring. Plan is to change filter first to see if that helps it. If not then drop the pan and go back to a standard oil pump and confirm pick-up height. I really don't think it is sucking the pan dry with the 7 quart. Any other thoughts would be appreciated.

centuryoldracer

Your oil filter has collapsed internally. The higher you rev it, the harder it pushes the collapsed element into the exit hole for the oil to flow through actually causing less oil pressure from the restriction.

mikem350

Filter bad or maybe the oil pickup screen is clogged.

toobroketoretire

It sounds like the pickup has come off. Its always best to tack-weld the pickup to the pump lid to ensure it never works itself loose. As easy as it is to pull the oil pan off I would just to check things out.

7T1vette

If the oil pickup tube fell off the pump, you would get ZERO oil pressure. You most likely have a collapsed oil filter which is blocking adequate oil flow. Use WIX filters and that won't happen again.

George Ries

hopefully your oil is not cavitating you might have to install aWindage tray in your oil pan or take a quart or two out and run only 5 quarts

George Ries

ii had this problem it will damage you rod and main bearings

toobroketoretire

Pull the pan off and you'll find the pickup has come off. As the oil pump is submerged in oil it'll continue to suck in oil until the level of the oil has reached the pump lid where the pickup is mounted. Once the oil level reaches that point it'll start sucking in air..............

7T1vette

Great thought...but the oil pump isn't submerged. That's why it needs a pickup tube.

blue427

If the oil filter is not the problem take your valve covers off and inspect your umbrella seals under the spings.Mine detiorated and wound up in the oil pan and under acceleration the pressure would drop,then when I let off the gas the pressure would come back up.The pieces of seal were blocking off the screen. The seals were not that old either.

RU7376vettes

Many thanks for all the input, hope to get new filter on tomorrow. Been raining and doctors got in way of working on it. Had other car on the lift, but will get to it tomorrow.

FYI- Engine has windage tray and I am pretty certain I had tack welded the pick-up to the pump body. Plan is change filter and test. If still a problem, will pull valve covers and check drains to make certain getting good flow back to pan, if still a problem will drop the pan.

Also hear 'story' that others using the 1218 filter had issues, but can't confirm. I have used Wix on other vehicles but stayed with Delco on the Corvettes and the 55.

Thanks again all,
Unk

centuryoldracer

Actually the oil pump is partially submerged, and if the oil level is full it will have pressure until it sucks air from starting, stopping, or cornering, or just sucking oil out of the pan faster than it can drain back.
It has happened to me more than once, and when it did, I just over filled it by a couple of quarts to get me home.

centuryoldracer

If it is the filter it was probably just a freak thing.
Let us know......

flyeri

I've been using the 1218 filter on my new GM crate motor just because it is under warranty. No issues, but not a lot of miles either. 30 on the first one, 500 on the second, and 2000 on the third. I had one more and it just got put on and will probably stay until next fall. I have Wix on all others except Subaru. I can't see how the quality can possibly be as good as Wix and some others when they are about $4.00 each.

Gale Banks 80'

Cut the old Filter and let us know what's going on in there.

Pop Chevy

I agree. Cut the oil filter apart 1st ! Put it in a vise, use a hacksaw if you don't have access to a bandsaw. I know it's messy. Cut a few of em apart and you will buy Wix filters from now on. Been doing it for years on my race cars.
If the filters o-k then you better drop the pan.

wombvette

High volume oil pump pumping oil up to the top , not returning fast enough.

GrandSportC3

I had a similar problem about 15 years ago with a '69 Vert that I owned.. Actually, when I was accelerating heavily, the oil pressure would drop to almost zero but it was fine when cruising.. It turned out to be a bearing issue and the engine eventually eventually had to be replaced.. I opted not to have it rebuilt and went with a 383 stroker instead of rebuilding it.... Probably wasn't too good of a idea as the engine was potentially the correct engine for the car.. The car had a state assigned VIN number. The engine had the correct 350/350 engine suffix and a '69 Vette VIN number stamped onto the block but it was not the VIN number that was asssigned to the car. (The car was a theft recovery and that's why it had a re-assigned VIN)

Kubs

I had bearing issues on my car do the same thing. I noticed the pressure was low sitting in the pits. I had 30psi at idle and then when I would rev it it would drop to 20psi. Bearing clearance was too tight and slowly wore away the bearing surface.

toobroketoretire

The only purpose of the pickup is to prevent cavitation at higher engine speeds. Otherwise you can run an engine without a pickup as long as the opening of the oil pump stays submerged in oil. The symptoms of a pickup coming off is exactly what you described; full oil pressure at low rpms then a sudden loss of pressure as the oil level reaches the opening where the pickup had been.

If your pickup did fall off put it back in and tack weld it to the pump lid with a MIG welder. MIG welding is cheap insurance and as new pickups are so cheap (about $5) its no big deal to toss it when the pump is finally worn out.