Oil Pressure..

[Broken_down?]

In the mroning my oil pressure gauge is right just about to the full mark, but after it warms up it drops way down. When checking the oil it is full.. whats the deal???

Rich

[Burnsman]

The viscosity of the oil decreases as the engine warms up. Ever try pouring gear lube out of a bottle when it's cold outside? It's like trying to pour molasses!

[Broken_down?]

I am using straight 30 weight oil Mobile. How can I keep the oil pressure up? I am afaird that if the oil becomes to thin it will not get on bearings and such.

Rich

[Burnsman]

A general rule of thumb is 10psi of oil pressure for every 1000 rpm. If it is more than that, I wouldn't worry about it. I have driven stock type vehicles that only had 15psi or so at idle. Never had a problem. I usually run higher pressure/volume pumps on my hot rod type cars and like to see at least 30psi when warmed up.

[Broken_down?]

can you recommed a better pump? I am not sure if I trust mine or not..

Rich

[Burnsman]

I usually run the Melling M55HV for the small blocks and the M77HV for the big blocks. I even run them in my race cars.

[lukecp]

How far down are you talking about?

The stock guage reads 60psi at the top mark...so the first mark is 15psi, second is 30, thrid is 45, and the last is 60.

A small block in good condition should peg the guage at startup, and run about in the middle once warm and you are just driving around. At idle it should dip to the first 15psi tick. I had an old 355 in my truck and it didn't even make it to the 1st tick at idle and it was fine.

So...which ones are you running at?

Oh, and BTW heavier oil will make a difference....putting some 20w50 in an older motor will raise the oil pressure a little bit and help make it stop smoking so much. And if the end is near, a quart of gear oil as mentioned above will also help out. But neither are permanet solutions

[Broken_down?]

When it starts in the morning it runs between the 45 and 60, but after it warms it drops @ idel to 15 and sometime abit lower ( I aqccount that part to being a quart low ) Is thi snormal?


rich

[Broken_down?]

also what grease oil brand and weight? for reference.. thx guys

Rich

[lukecp]

15psi at idle....even 7.5 is normal and OK for an older high mileage small block chevy. If it was recently rebuilt i would be a bit worried though.

[old Rusty C10]

my guage tops out when i start the truck in the morning and as it warms up it drops , but whe the truck is totally warmed up and driving in regular city driving at idle in drive at a light its about 15-20PSI after any load it goes to 30 and slightly higher as you accellerate but within the normal range i run 10W30 in mine

[71-longbed]

my old 350 sits at 45 psi during start up ... 30psi at idle when warmed up and a hair below 45 psi while warmed up and cruising ...

i use 10w40

[1972C10]

That M55Hv is a good pump the M99hvs is a good pump if you want hellacious pressure and high volume i run the plain 55hv in most of my strett vehicles it all depends on how tight the motor is too i bent the stock oil pressure gauge in my 72 it wont go all the way back down to 0 now

I run 10w40 and it idles at about 30 and gets to where i cant see the needle at 3000 rpm

[jhow66]

From reading your post it sounds like you think that your gauge is telling you how much oil you have in pan. As long as your pump pickup is under oil the pressure will read the same whether there is 2 qts. or 4 qts. etc. in pan. The clearance of your bearings, the weight of your oil , the RPM of engine and the temp. of oil dictates how much oil pressure you have along with the strength of bypass spring in pump. 10 lbs. at idle is fine on a stock motor.

[shuttermutt]

My 350 running 5W30 pegs the gauge at startup. Once we're at operating temperature, it reads about 45 while driving, 30 while idling in Park, and 15 while idling in gear.

[Broken_down?]

My 350 running 5W30 pegs the gauge at startup. Once we're at operating temperature, it reads about 45 while driving, 30 while idling in Park, and 15 while idling in gear.

Thats sounds what mine runs like. excpet the pegging part.

rich

[JadeEmperor]

From what I've read here, I'm not sure if I have a problem I should look into. At start mine pegs out. After warming and at idle it runs just above mid (30 psi). While cruising is runs around the third mark (45 psi). Any issues in your opinion?

OT: I also have a 91 Blazer with a 4.3 V6 that runs full tilt even after warm, expecially during acceleration or reving. Problem?

Thanks!

[shuttermutt]

Nope! Sounds pretty good to me.

[lukecp]

30psi at idle is great oil pressure....you have no problem at all

Too much oil pressure will eat horsepower anyway.

[BUXMAN66]

don't make too much of this oil pressure problem guys. if you have 45-60 at start up.....and then a nominal decrease to 30-45 at cruising speed .....7-15 at idle... you have no issues. actually too much oil pressure is a h.p. robber and a potential for blow-by through the pcv or the breather cap. either too much or too little is only cause for alarm. too much: crap in your oil passages blocking oiling points,like using an oil that is known for having a lot of parafin (filler) which makes sludge in the oil pan. to little: again possibly plugged pick-up from sludge(i've seen it!), bad pump, excessive blow-by from faulty rings,....etc. reasons can go on and on....

[JadeEmperor]

Thanks everyone. I can sleep better at night now. The wonders and depth of knowledge on this board never cease to amaze me.

[Grim Reaper]

Chevy motor will idle with 2psi of pil pressure and not rattle the lifters. I drove one for 1.5 years like that with bad thrust bearing and a walking crank. I could punch it and get off it at hwy speeds and get an extra 5 psi out of it. NEVER any audible sounds and hot with 20w50 it was doing god to get 15psi at 3k.


NEVER use 10w40 dino oil . 10w40 is 10w30 with parifin to thicken it up. GM will point blank void your warranty if they find you have run it and you have a oilsystem failure. It cokes on the rings and causes all sorts of problems. 10w40 synthetic is ok in most cases. Diferent process to make it that thick.

[jhow66]

What has oil pressure got to do with blow-by?

[Grim Reaper]

Originally posted by jhow66
What has oil pressure got to do with blow-by?

Not to use 10w40 to fix your pressure problem. Go to 20w50 if your going to try that approach. It doesn't work but everybody tries it.

[shuttermutt]

Actually, moving to a heavier oil will not help and could, in fact, be worse. Consider moving to a synthetic 10W30 or even 5W30. Pouring concrete into a worn engine will only result in accelerated wear.

Not that I'd try this at home, but some of the old school guys will actually overfill the crankcase by 1/3 to 1/2 quart on tired engines. Personally, I think they're nuts, but there might be something to it, too. Who knows?