1979 351w oil pressure and oil weight

[dominickbuff]

I have a 1979 351w engine and have low oil pressure at temp(good oil pressure when cold) I am currently running 10-40 will going to 20-50 help?

Engine has 250k miles and has never been rebuilt

I have confirmed the oil pressure with a mechanical gauge

 

[Chris142]

How low is the pressure?

 

[eljefino]

It will help but it might be time to start motor shopping.

 

[JavierH19]

Many engines can have low oil pressure and be fine and last a long time. There could possibly some slight internal leak inside the oiling system where pressure is escaping but that's not a big deal. But what exactly are the numbers. And yes 20w-50 is fine to use, I'd use m1 15w-50 for the better additive pack instead.

 

[bullwinkle]

Mystik JT-8 15W50 would work well too, although it might be better if the catalytic converter disappeared…

 

[dominickbuff]

How low is the pressure?

3-4 psi when hot

 

[dominickbuff]

Many engines can have low oil pressure and be fine and last a long time. There could possibly some slight internal leak inside the oiling system where pressure is escaping but that's not a big deal. But what exactly are the numbers. And yes 20w-50 is fine to use, I'd use m1 15w-50 for the better additive pack instead.

It has 3-4 psi when warm

 

[Chris142]

3-4 psi when hot

Idle?

 

[dominickbuff]

It will help but it might be time to start motor shopping.

How low is the pressure?

3-4 psi

 

[dominickbuff]

Idle?

And driving (haven’t taken it over 30mph) but psi is good when cold

 

[eljefino]

Do you have an interest in keeping this original? A 351 from that era might be pretty low performing.

 

[Chris142]

And driving (haven’t taken it over 30mph) but psi is good when cold

4 psi driving??

 

[JavierH19]

It has 3-4 psi when warm

That's around the ballpark for an old 351. You should use m1 15w-50 which you can get at any walmart. Another common thing to do is put a high volume oil pump on it. Not a big job on this old engine you could do it in a day taking your time.

 

[dominickbuff]

Do you have an interest in keeping this original? A 351 from that era might be pretty low performing.

It’s in a van so performance isn’t to big of a deal

 

[dominickbuff]

4 psi driving??

Yes

 

[JavierH19]

Yes

Change the oil pump with an upgraded one like the melling m83hv which is a solid choice. The high volume pumps are pretty cheap most are a hundred or less.

 

[Chris142]

Yes

You cant drive with only 4 psi. You will damage the engine quickly. Time to pull the pan and roll in bearings and a pump,then hope the cam bearings are good enough.

 

[joegreen]

Yes dont drive this unless you want to put in another engine. Oil pumps do wear out. I had 20-40 psi on my old sbc. Changed the oil pump for a stock replacement and now have 60-70 psi. No other changes.

 

[dominickbuff]

Yes dont drive this unless you want to put in another engine. Oil pumps do wear out. I had 20-40 psi on my old sbc. Changed the oil pump for a stock replacement and now have 60-70 psi. No other changes.

I ordered the pump it will be in later in the week…

 

[Lubener]

I have a 1979 351w engine and have low oil pressure at temp(good oil pressure when cold) I am currently running 10-40 will going to 20-50 help?

Engine has 250k miles and has never been rebuilt

I have confirmed the oil pressure with a mechanical gauge

Specs are 40-60 psi when warm at 2000 rpm. If you had 3-4 psi, the engine would be very noisy. If indeed low, 20-50 oil will help but not much. . Sounds like the bearings are bad after that many miles but the oil pump pickup screen could be sludged up. . I would pull the oil pan and plastigauge the bearings to see if they are worn and a new oil pump as well.