sbc 350 oil pressure from 60 to 5

[1977C20Silverado]

Backstory: I started it up fine and it was idling at 45 psi, which has been pretty normal lately. I figured it was just cause its been a little colder. As i got offroad it went down to about 30 psi. Then i went offroad and i noticed it didnt sound like it was firing right, but i was already up there and its done that before with no issue. Then as i get back on the road i speed up to about 50 and i realize the oil pressure is at 60. so i let off and stop at a red light, and it drops down to around 5 psi and the motor dies. It started fine and i drove about a half mile to a parking lot and stopped it at about 25 psi. anyone else had this issue and what could it be?

 

[DoubleDingo]

Is the oil full? When was the last time you changed it? Are you running a thin oil, thick oil? 45 and 60 psi is not bad. 5 is not good. Could be the gauge. Could be bearing clearances have gotten wider. Was there noise in the engine? Knocking? Ticking?

 

[1977C20Silverado]

Is the oil full? When was the last time you changed it? Are you running a thin oil, thick oil? 45 and 60 psi is not bad. 5 is not good. Could be the gauge. Could be bearing clearances have gotten wider. Was there noise in the engine? Knocking? Ticking?

It’s got good oil level, it’s 10w30 and I’ve put on about 600 miles since the last change. I just started it and it’s idling good around 20 psi. Idk what was wrong but it’s not happening now

 

[82sbshortbed]

Mechanical or electrical gage?

 

[1977C20Silverado]

Mechanical or electrical gage?

Mechanical. And it dropped down to around 10 after driving for a few miles and stopping, but it was still idling good

 

[DoubleDingo]

Knocking?

 

[1977C20Silverado]

Knocking?

nope. Running pretty much perfect. When I went off road earlier it started sputtering and I could tell it wasn’t firing right but it’s done that before and usually stops once I get to level ground. And once I got back onto the road it started running good again so idk

 

[DoubleDingo]

Get a mechanical oil pressure gauge, plumb it in and check it with that.

 

[Ricko1966]

Sputtering off road is most likely fuel spilling over from the carb. Oil pressure and how the engine is running is probably not related,they can be running fantastic and have low oil pressure. @DoubleDingo said check it with another gauge,good advice,. If oil pressure remains close to 10psi per 1000 engine rpm I wouldn't worry about it. Oil pressure that comes and goes,after ruling out the gauge,I'd by looking for trash in the oil pan restricting the pickup,or a sticking oil pressure relief valve.

 

[F-64]

10w-30 may be a little thin. You may try a 10w-40.
I had this issue with an air-cooled motorcycle.
With 10w-40 at idle, the oil pressure light would come on. Ambient temps around 80°F.
Switched to 20w-50 and the problem went away.
Your engine may also have looser tolerances due to wear.

 

[bucket]

With a Chevy small block, all that's required is 10 psi for every 1000 rpm.

With that said, it sounds like a gauge that has gone wonky. I'd change it with a quality (mechanical, not electric) unit and go from there.

 

[BlazerBill]

Could someone please provide the brand and part numbers of a good quality oil pressure sending unit and mechanical gauge for my ‘83 K5 with the new GM SBC SP350 crate (385hp/405 torque) that I’ll soon be installing? Summit Racing lists several brands and with varying pressure ranges and I’m not sure which of these I should go with.

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[DoubleDingo]

Do you have a Napa, O'reilly's, Auto Zone, Advance Auto in town? Just get one from them.

 

[Fat 454]

honest question - why would you recommend mechanical rather than electrical? I would have thought having a wire running the length to under the dash would be easier than a pipe, provide a faster signal, and not have the potential issue of a messy leak in the cab. I am assuming the electrical plumbs into a "mechanical" pressure sender on the engine block - what am I missing??

 

[Ricko1966]

Mechanical VS. Electric both have pros and cons. It all depends on who you are talking too. My personal opinion is a name brand gauge Mechanical or Electric will do fine,make sure to buy the correct sender if you go electric. People are going to say the sender can go bad,the wire can short etc.,but nylon or steel tubes can get holes or get brittle and crack and pump your engine oil where ever. I've heard of nylon tubing getting burned on headers and sealing the gauge end shut and allowing the engine side to pump the pan dry, I'd call B.S. on that but IDK. As I said positive and negative on each,pick your poison.