350 chevy with low to no oil pressure

Agree..

20w50 and STP added cold to an engine cannot be good on a motor..

 

Why not, I left the house and drove a mile on a new pump (less than 500 miles) in the '90s and my oil pressure dropped to zero. By p*** stuck.

Oil change to something called 20-50 oil treatment could have knocked something loose and it stuck in the by p***.

 

the primer is an old dizzy modified to fit my drill with the gear off...

I added the 20-50 oil a while ago and it ran fine, I've also used stp oil treat with most oil changes.

 

I don't think the 20-50 is a problem unless it was 20* out, you'd have hard cranking at that time as well.

Bob

 

Yeah but if he has been adding STP at every change from the gito, and adding it cold, it is a major viscosity builder the oil will be way thicker than 20-50 if it mixed, if it didn't it is glommed all over the pickup tube and screen. I have torn them down with that stuff hanging all over in the bottom of the engine and ****ing what little oil it could get threw a hole in the screen smaller than the end of your little finger. Usually was to late for the main bearings.

 

I've seen it too, but on worn engines with much more than 8K miles on them. I posted earlier that it can turn to wax under the right conditions. If the current STP is close to the old STP, anything is possible.

Bob

 

Just because the engine has 8K miles doesn't mean it has tight clearances.But thick oil with that STP **** and running the engine hard before it's fully warmed up might lead to a problem.
It could time to pull the pan and or the timing cover to have a look inside..

 

Yeah, gotta get into it to see what's what. I realy don't see why anyone uses STP any more. I only used it when I had an engine that had an insatiable thirst for oil.

Bob

 

Try a lighter oil!run some "seafoam" & see what happens.I'm on my 3rd engine, at least my 4th gauge & i never get more then 25 lbs pressure hot out of any SBC..it seems the "trend" in motor oils is lighter now, 5w-30,10w-30 or 40! I can't seem to see it but they say thats good now!
JimV

 

Its worth a shot and easy enough to do. I always had decent pressure in my Chevys unless it was a super hi-miler. Any engine in good condition I'd run 10W-40 in it year round. 20W-50 or straight 50 was reserved for the oil guzzlers.

Bob

 

We had the exact experience with a vintage dirt track car. Power was a 250 Chevy six. It was the oil pump relief hanging up. Changed the oil & no pressure. Pulled the distributor & primed via drill. Oil pressure came up but I could tell from the light load on the drill that something wasn't right. We were at the track & just as we were going to take the green for hot laps my son pulled off with no oil pressure. Once back in the pits, if the rpm was held to around 2,000 the oil would slowly lube the rockers, (looked through the valve cover fill cap) and very slowly crawl up the plastic tube to the mechanical guage. Son ran it that night anyway. Instructed him to keep rpm up and if race was red flagged to shut engine down asap. Got away with it ok. Replaced pump next week & all was well. 50 psi at idle thereafter with new pump. Later traded motor to a race buddy, (told him the scoop too) for some parts & it is still going.

Change your pump. That's my bet.

Good luck,
Worken2much

 

pulled the motor today, no chunks of any kind in the pan...yeaaa....

Oil pump felt and sounded sluggish with my drill on the shaft. the spring was ok but I think the gears have worn and the pick up tube was not welded in, just pressed in, and looked like it had moved some, the pickup screen was fine...some good wear marks on the pump cover and sides....I am ordering a new pump and we'll see,



If I wanted to, could I pull one of the mains and check bearing clearances with plastiguage?

 

time for an update....
bought a new Melling 55A pump and installed it,,,, and just put the engine back in this weekend and started it today and i have good oil pressure with 10W30...so at least this one has come full circle...

 

Now do yourself the next favor. Get rid of the plastic oil pressure line if the engine means anything to you. Go steel braided line to a mechanical gauge or go electric gauge. Plastic oil pressure line is cheap in parts store form. It's not as good as what Imperial Eastman used for hydraulic cylinder service work in the '70's. I damn near lost an engine from the **** 20 some years ago and I refuse to use plastic oil pressure line today.

 

good point....I bought an extra one to test my oil pressure while it was on the stand with my SW mech gauge and my 1/2 drill and oi primer....they have the copped one maybe i'll take a look at that.