The Stovebolt Site Forums The Shop Area Engine Shop Oil Pressure

Hi, this is my first post and I am new to 6 cylinders. I need to know what is decent oil pressure for a 250 engine. I just got a 64 pickup which had sit for some time. Got it running today and I am getting a lot of blowby out of the breather and oil pressure was about 30 at startup and after warn up it dropped to around 22 . As the rpm goes up it will raise to 28 when hot. Is this normal or is my pressure too low? I know this would suck on a V8. Hope to change oil and run it some tomorrow to see if the blowby improves. Any info would be appreciated.
James Lewis

James,

It sounds like the engine might have quite a few miles on it. Although not at the top of the pressure range, I think it is adequate to lubricate the engine properly.

You might want to change the oil, and when doing so, consider a multi-grade, or at least one step up in viscosity.

Make sure you don't have a fuel dilution problem from a leaking fuel pump... this could be indicated by a overfilled crankcase, oil that smells of fuel or oil that appears very thin in viscosity. You have the right idea...change it and check it!

Stuart

Stuart,

Thanks for the reply. I'm going to change oil tomorrow and also check for gas in oil although I didn't smell any. I'll probably eventually go thru the engine but for now, I just want to get the dents straightened out and shoot some primer on the truck. I hope to paint it this spring.
James

James,

I see you are from Garland...isn't this a suburb (?) of Dallas? I know I have seen at least one other member of this forum from Garland, and I deal with Industrial Woodworking who I believe is headquartered in Garland also.

Good luck on the truck, and it isn't against the "Bolt Law" to put a VI (viscosity index)improver in when you change the oil. These are additives for high mileage rigs that help keep the blood pressure up until the inevitable rebuild.


Stuart

James, welcome to the bolt, a good place to hang out and have fun plus learn neat stuff too.. several are from the DFW area, check out the site map and see where they are plus you might want to pin it also.. regards...Fred

Joker and Stuart,
Thanks for the info. I am recently retired and just getting around to the old chevy 6 cylinder thing. I always had small block cars before but decided to try something different with the 51 and 64 Chevy trucks. Besides I am just getting too lazy to swap engines and I already have enough gas burners anyway.

Yes, Stuart Garland is just east of Dallas . I am Texas born and raised but left in 1977 for a job in St Louis and then Cincinnati so it took me 18 years to get back. I don't intend to leave again. I also am new to the computer thing, took it up during a recovery from a major surgery. Love these forums.
James

Try adding a quart of ATF when you change your oil, the ATF will help to clean-up the carbon deposit that may be on the rings and around the valves. I like to do this on engines that have been sitting for long periods of time and for engines that I have no history on. My dad used to drain his oil and then fill the crankcase with diesel, run the engine for a few minutes, drain, then add clean oil. He belived this would clean all the deposits and crap from the motor, he never had any problems with bad rings, low oil pressure, or lack of compression.

roberr54,

I have used almost those same methods myself. The Dexron in the GM spec ATF is suppose to be the additive that attacks varnish, etc and holds
it in suspension until the oil is drained. A dose of ATF was the secret cure for noisy hydraulic lifters.

There are modern day engine flushes available at your FLAPS. I have used these and they seem to clean the engine to some degree.

Standard Oil Company used to make a product called PDQ Engine Cleaner. It was nasty, but did a hell of a job...if the engine survived, it was clean. It was sometimes used to clean the internals prior to a tear down and rebuild. I always loved the name...PDQ!

Stuart

Hi Neighbor. I looked it up and the oil pressure at 2000 rpm for a 1970 -79 250 i6 is supposed to be 40 psi. Are you reading it at the sender with a mechanical gauge or using the truck's gauge? There is the possiblity that the truck's gauge could be a bit off. However, it seems pretty accurate after all these years on my 59 1 ton (292).

As for blow by, well, bottom line, its probably rings. Since we don't get all that much cold weather you could try a heavier straight weight oil. I use plain old 30w heavy duty in the 292. A multigrade would be easier to blow.

Thanks for all the replies, I am going to flush out the engine and put in straight 30 weight oil for now. The engine is somewhat hard to start but other than the low pressure runs ok. All I did to get it running was new plugs and fresh gas. I will do a complete tune up and see how that goes. I have no idea how many miles and suspect it is just tired. I always liked to see about 40 psi pressure on all my engines but didn't know if the old six ran at lower pressure. Sounds like a rebuild down the road. Will add a split manifold and a couple more carbs at that time. Just have to hot rod it up .I want to get the body in good shape first but I probably will have to convert to power steering as I am having a hell of a time adjusting to manual steering after all the years of power steering.
James

OK, final update and here is what I did. Drained old oil, put in a gallon of diesel, ran the engine for three minutes. Drained the diesel and replaced with used oil from my wife's car. Ran for 3 minutes and then drained. Put in new 30 wt. Also cleaned the breather cap and pcv valve. Let it sit for 2 hours and started it up. Had 40 psi at idle. Let it run 10 minutes and pressure dropped to 32 at idle. Will build up to just under 40 at higher rpm. Blowby was much improved. I'm satisfied for now if I don't run it hard things will be ok for a while. Now it's on to the body. Thanks everybody for your input.
James

James,

You have much bigger cajones than I...diesel for 3 minutes, WOW. Did you happen to read the oil pressure when that was going on?


Stuart

Actually it was about 2 minutes and no, I was outside the truck and in such a hurry to shut it off I didn't look. I only let it idle. I am going to try running it more this weekend if the weather cooperates.
James

anywhere between 15 to 30 hot is acceptable for these engines.mine runs 60 psi hot going down the road and 40 idleing but it has a melling Hi volume pump

that deisel thing sounds crazy,but i have a tiny six(216) thats got the same problem,cant afford a bigger,better motor now but can afford a gallon of deisel,i'm goin for it,gonna see if it helps out the little 216,yeah its gutless but it keeps me putt'n down the road,i hope this deisel thing dont backfire on me!Oh yeah,that ATF trick,do you add and then drain or does that stay in?

If you use the diesel just run it long enough to pump oil thru the engine. I think about 20 seconds would be enough. I really pushed it but I figured my engine was probably shot anyway. It is however running ok and holding just under 38 lbs hot now. Sure was dirty inside. Good luck.
James

Sorry to revive an old post, but the search button is my friend as I am new to this...

I have a 1949 3100 with a 1970 250 engine. Oil sender is on pass side with the line going into the back of my stock (I believe) gauge. Gauge only goes to 30 so it is pinned at 30 when it runs.

Do I need a new gauge? From searching, looks like the pressure should be above 30, but I cannot find a spec.

Would prefer a "stock" type gauge if possible.

Thanks