1969 Oil pressure/gauge problem. Help

[Brian M.]

69 350/300hp 66k original miles, original engine, original smog equipment

After driving 20 minutes my oil pressure gauge drops to almost zero when I idle at a stop light. Step on the gas and it reads just fine. My restoration shop changed the gauge but on the way home, same problem.

- thoughts?
- is the oil pressure line suppost to be black plastic, for a small block??
- My Chevy dealer wants to run a copper line. My other old cars have a copper line.

Thanks in advance

[Jim M.]

Re: 1969 Oil pressure/gauge problem. Help

Brian, My 69 350/350 has a black plastic line.

[Joe L.]

Re: 1969 Oil pressure/gauge problem. Help

69 350/300hp 66k original miles, original engine, original smog equipment

After driving 20 minutes my oil pressure gauge drops to almost zero when I idle at a stop light. Step on the gas and it reads just fine. My restoration shop changed the gauge but on the way home, same problem.

- thoughts?
- is the oil pressure line suppost to be black plastic, for a small block??
- My Chevy dealer wants to run a copper line. My other old cars have a copper line.

Thanks in advance

Brian------


All 1969 small blocks used a black nylon (plastic) oil gauge line.

My 1969 small block read very low oil pressure at idle from the day it was new. However, it did not read zero. So, I'd say it depends upon just how close to zero yours reads to say if there's an engine problem, or not.

To get a handle on this, install an accurate TEST GAUGE. Simply remove the fitting at the block and install the test gauge line to that fitting. Then, you'll know how much REAL oil pressure you have at idle. I think you'll find it will be more than your in-car gauge reads. However, you don't need very much oil pressure at idle.

[Jerry B.]

Re: 1969 Oil pressure/gauge problem. Help

Joe, what is the ideal oil pump for a 350/350?

[Brian M.]

Re: 1969 Oil pressure/gauge problem. Help

Thanks for the responses. The Chevy dealer did hook up a Test Gauge and indicated no problem with the pressure at idle. However I didn't ask the dealer what the Test Gauge pressure was reading at idle. I'll have them re-perform the test.

FYI: My Chevy dealer is great. I deal with the head of service and they treat all of my cars as if they were there own.

As far as the comment on how low my in car gauge is reading at idle: It concerns me as my in car gauge drops to what looks like zero. Yep, flat line. I don't see much if any room from the zero mark.

Thanks again

[Brian M.]

Re: 1969 Oil pressure/gauge problem. Help

The Chevy dealers says using a Master Test Guage the oil pressure at idle, with the engine hot, is 25 to 30 lbs.

Sounds great to me, but I'm still going to be sick to my stomach to see the in-car gauge read basically zero. I'm having the dealer install small diameter copper tubing instead of the black plastic/nylon tubing. I'm not saying this will help, but I'll feel better.

If I didn't have the same issue with the "original" gauge, I'd replace the gauge again.

[Chuck G.]

Re: 1969 Oil pressure/gauge problem. Help

Couple of thoughts.

Is this a recent problem? Was the idle oil pressure higher in the recent past?

What weight oil are you running? Multi grade? Synthetic? 5-30 or 5-40?

What is the engine temperature? Higher temps thin out the oil.

Chuck

[Dick W.]

Re: 1969 Oil pressure/gauge problem. Help

[quote=Brian McCrackin (20151);553933[B][/B]I'm having the dealer install small diameter copper tubing instead of the black plastic/nylon tubing. I'm not saying this will help, but I'll feel better.

quote]

DO NOT INSTALL A COPPER LINE! COPPER WILL WORK HARDEN FROM VIBRATION AND CRACK! GM DID NOT USE A COPPER LINE ON ANY CORVETTE FOR THIS REASON!

[John H.]

Re: 1969 Oil pressure/gauge problem. Help

I'm having the dealer install small diameter copper tubing

Brian -

As Dick noted, this is not a great idea; GM never used copper tubing - they used copper-plated steel tubing (during those years where they used metallic lines). In any case, using a metallic vs. the orignal nylon pressure line won't make any difference in the gauge reading.

[Joe L.]

Re: 1969 Oil pressure/gauge problem. Help

The Chevy dealers says using a Master Test Guage the oil pressure at idle, with the engine hot, is 25 to 30 lbs.

Sounds great to me, but I'm still going to be sick to my stomach to see the in-car gauge read basically zero. I'm having the dealer install small diameter copper tubing instead of the black plastic/nylon tubing. I'm not saying this will help, but I'll feel better.

If I didn't have the same issue with the "original" gauge, I'd replace the gauge again.

Brian------


I'm a bit surprised that the idle oil pressure was that high. I would expect more like 10-15 lbs.

[Joe L.]

Re: 1969 Oil pressure/gauge problem. Help

Joe, what is the ideal oil pump for a 350/350?

Jerry------


I would recommend a GM #12555284 or a Melling #10553 (these might now actually be exactly the same piece).

[Brian M.]

Re: 1969 Oil pressure/gauge problem. Help

Wow! Thanks for the fast replies and getting me back on the right track.

I'll call the Chevy dealer and have them leave the Black Nylon/Plastic line on the car. No copper line ...Got It.

Chuck,
Not sure of the actual temp, but I don't believe it's over 210. It's not running hot. It overheated last summer when I blew a belt, but that's it. I bought this Corvette 18 months ago and had all the fluids changed. Yes, the Oil has been changed a few times, but I'm ebarrased to say I don't know the grade. I don't drive this Vette too often as my 61 2x4 270hp Vette and 69 396/375hp Camaro get most of the miles. The 69 Vette doesn't burn oil, so I just tell the Corvette restoration shop to change the oil when it goes in for it's Winter or Spring visits.

I started to notice the issue late last summer, but I really hadn't driven many non-highway miles before then. So the issue may have existed after the first Oil change.

I'll call tomorrow and get the type and grade of oil.

Thanks again, your feedback has been far beyond my expectation. It makes me want to buy another Vette, just to support the hobby.

[Dick W.]

Re: 1969 Oil pressure/gauge problem. Help

Brian, those guages have a tendency to stick. I have removed them, cleaned the pivot points with a good penetrating oil, and lubed them with a good gun oil, a small drop on each pivot.

[Brian M.]

Re: 1969 Oil pressure/gauge problem. Help

Responding to: "those guages have a tendency to stick. I have removed them, cleaned the pivot points with a good penetrating oil, and lubed them with a good gun oil, a small drop on each pivot"

Thanks Dick

I'll give it a try. I originally ruled out an issue with the gauge, as the original and replacement restoration gauge exhibited the same issue. But the movement on the gauge certinally isn't smooth.

Brian

[Jerry B.]

Re: 1969 Oil pressure/gauge problem. Help

Thanks Joe