Slant oil pressure seems low?

[RGAZ]

73 Stock slant, $93K miles original.

So I normally use 10W30 synthetic and saw pressures of 30PSI at cruise and lows started getting down to <10psi hot at idle. So last change I went with VR1 20W50 and now I get 40 psi cruising and barely 12 at hot idle. Should I:

1. Service the pressure relief valve (pull and buff)
2. Replace the pressure relief valve spring with higher?
3. Replace the pump?
4. Do nothing as this is normal because the engine is beat.
5. something else?

Not too worried, just making a plan.

RGAZ

 

[Charrlie_S]

1) I would. Fairly easy to do, and could be the cause of the problem
2) No. That would not have any effect on idle oil pressure, only max oil pressure if pump and engine are in good condition.
3) Possibly. This could be the problem but depends on whether the pump is the original pump.
4) I would do something. At the minimum some diagnosis.
5) Decide what you want the car to do, and what you can spend. If just a beater, and spend minimum amount of money, do #1 and use a inexpensive 20-40 oil.
If you want a "cruiser", plan on possibly removing the pan and checking from sludge blocking the pickup, or warn bearings, if #1 or #3 don't cure the issue.

 

[66fs]

73 Stock slant, $93K miles original.

So I normally use 10W30 synthetic and saw pressures of 30PSI at cruise and lows started getting down to <10psi hot at idle. So last change I went with VR1 20W40 and now I get 40 psi cruising and barely 12 at hot idle. Should I:

1. Service the pressure relief valve (pull and buff)
2. Replace the pressure relief valve spring with higher?
3. Replace the pump?
4. Do nothing as this is normal because the engine is beat.
5. something else?

Not too worried, just making a plan.

RGAZ

Probably worn rod bearings. Never touch the relief valve, if you round the sharp edges it will cause excessive pressure spikes. A higher pressure spring (high pressure spring from a big block) will only move the pressure higher at cruise. Try 20w50 Valvoline VR1. It seems the pump is OK, maybe high volume? But really not too much to worry about, 10 psi per 1,000 rpm. What filter are you running.

 

[RGAZ]

Probably worn rod bearings. Never touch the relief valve, if you round the sharp edges it will cause excessive pressure spikes. A higher pressure spring (high pressure spring from a big block) will only move the pressure higher at cruise. Try 20w50 Valvoline VR1. It seems the pump is OK, maybe high volume? But really not too much to worry about, 10 psi per 1,000 rpm. What filter are you running.

Already have VR1 2-50 in it. Just a Fram on it for now. Engine does not seem sludgy.

 

[66fs]

I thought that, never saw 20w40 VR1. Has it always run those pressures since you had it? Sorry to say, I doubt it is the oil pump.

 

[RGAZ]

I thought that, never saw 20w40 VR1. Has it always run those pressures since you had it? Sorry to say, I doubt it is the oil pump.

Yeah, sorry, typo. I only have driven the car about 3000 miles since I got it and the previous gauge on it was a really bad electrical that I did not trust. Now I have two mechanicals on it and I am wondering about my options.

 

[Dave999]

I'd check the pump cover for scoring. polish it flat again on wet-n dry paper sitting on glass or similarly flat work top
if you can see the arc of the impellers carved into the cover it needs work
check the impeller clearances are within spec, drive to driven ring lobe distances
if you can check that the bore of the pump body is not worn where the impeller shaft comes through
make sure i have an oil filter of good quality to appropriate specification.

my upright six

50-60 when stone cold then very quickly drops to 40. presume that small piston is inching back...
40 at speed when hot all the time this must be maintained i think by the pump spring and piston once i get to 4500 rpm it never gets any higher.
10-15 at idle when hot
always strived for 318 like oil pressure never got there.

doesn't matter what i do
its been rebuilt and checked the pump blueprinted the pickup checked for cracks and positioning above sump
oil pump braced to avoid flex away from drive, mine hangs of the block rail in a particularly vulnerable way, they snap off their mounts hence i fitted a mount saving brace to the nearest main cap stud.....
sump baffle
windage tray

always the same....

been apart a few times no noticeable degradation seen to rod or main bearings
been like this for 20 years does a couple 1000 miles a year

this is a 7 main bearing crank motor with the rockers fed through the pushrods...
different yeah but not that different in respect to the pump design...

Dave

 

[Mike69cuda]

A general rule of thumb used to be 10 psi per 1000 rpm. Sounds like you are ok to me, unless you are looking for a project.

 

[66fs]

Yeah, sorry, typo. I only have driven the car about 3000 miles since I got it and the previous gauge on it was a really bad electrical that I did not trust. Now I have two mechanicals on it and I am wondering about my options.

I agree with Mike69cuda, probably last forever if you keep good oil in it and change it often. My Jeep Cherokee has 140,000 miles on it and does the same. It has been like that for 10 years. I'm not afraid to drive it anywhere.

 

[RustyRatRod]

I don't see an oil pressure issue. What is the idle RPM? 650? 700? It's got plenty.

 

[RGAZ]

Yeah, 650-700. Ok I’ll let it go.

Thanks guys.

RGAZ

 

[slantsixdan]

12 pounds at idle is within spec. Still, it will be a good idea to service the oil pressure relief valve to make sure it's doing its job, as described in these two threads: thread 1, thread 2.

Unless your engine is on its last legs and you're trying to squeeze a last few miles out of it, go back to 10W-30.

 

[RGAZ]

Thanks SSD, I already had those awesome threads from my forum search, the issue I am running into is that it’s not easy to find “real” crocus cloth. All the Chineseium stuff is the wrong grit. I found it on McMaster Carr but don’t need 30 feet (lol).

I’ll see what I can get and follow your instructions.

Thanks again
RGAZ

 

[Mike69cuda]

The biggest problem with fixing something that isn’t broke is that you often break something else in the process….

 

[RGAZ]

The biggest problem with fixing something that isn’t broke is that you often break something else in the process….

Truer words have never been spoken.

 

[slantsixdan]

Thanks SSD, I already had those awesome threads from my forum search, the issue I am running into is that it’s not easy to find “real” crocus cloth.

Really? Huh. Been awhile since I needed to buy any, but not that long awhile. It's still available by the sheet at my local hardware store, pretty much the same stuff it's always been.

 

[Charrlie_S]

Really? Huh. Been awhile since I needed to buy any, but not that long awhile. It's still available by the sheet at my local hardware store, pretty much the same stuff it's always been.

I had the same problem. Had to order it online. Local, could get emery paper, but not crocus cloth. (Cloth backed, not paper backed)

 

[66fs]

Thanks SSD, I already had those awesome threads from my forum search, the issue I am running into is that it’s not easy to find “real” crocus cloth. All the Chineseium stuff is the wrong grit. I found it on McMaster Carr but don’t need 30 feet (lol).

I’ll see what I can get and follow your instructions.

Thanks again
RGAZ

I use wet or dry 600 grit with WD40 to polish engine parts. Valves, rod sides, crank journals, etc. Since you are in Greenwood, I could also run it through the ultrasonic cleaner. But at the end of the day, I doubt it will change anything. I'd still run 20w50 VR1 if it was mine, it has never hurt any engine of mine. We do live in SC.

 

[RGAZ]

I use wet or dry 600 grit with WD40 to polish engine parts. Valves, rod sides, crank journals, etc. Since you are in Greenwood, I could also run it through the ultrasonic cleaner. But at the end of the day, I doubt it will change anything. I'd still run 20w50 VR1 if it was mine, it has never hurt any engine of mine. We do live in SC.

Thanks, I will pull it out this weekend and see how it looks. I may just clean it and stuff it back in. If not I will hit you up.

 

[TF360]

Just a thought for you, I use Lucas Hot Rod and Classic 10w40. I always ran 10w40 in my Slants. It's a little thicker for the warmer Temps in the south.

 

[slantsixdan]

Just a thought for you, I use Lucas Hot Rod and Classic 10w40. I always ran 10w40 in my Slants. It's a little thicker for the warmer Temps in the south.

This is faulty logic (living in the south is not a valid reason for using 10W40, and 10W40 is not better than 10W30…not even in the south).

×2 because that Lucas stuff is fraudulent. It can't help and can hurt.

 

[TF360]

This is faulty logic (living in the south is not a valid reason for using 10W40, and 10W40 is not better than 10W30…not even in the south).

×2 because that Lucas stuff is fraudulent. It can't help and can hurt.

No Dan, I'm referring to the Motor Oil from Lucas, not the Oil Stabilizer. You sent an article on Stabilizer. It's not faulty Logic either. Our Classics call for thicker oil in warmer Climates per the Service Manuel.

 

[RGAZ]

Guys, thanks for the great answers and insight, I appreciate it.

Thanks,
RGAZ

 

[slantsixdan]

No Dan, I'm referring to the Motor Oil from Lucas

Yeah, I know. Thing is, they lie so much about their oil "stabilizer" that I don't trust them to tell the truth about anything else they sell. And since there are so many options in legitimate, non-lying brands of proven-good oil, for less money, it's kind of an easy pick. But oil selection is a religious matter for a lot of people, and religious beliefs don't really bend for puny facts and science and stuff, so…carry on!

Our Classics call for thicker oil in warmer Climates per the Service Manuel.

Not quite, no. Look again/closer at the oil viscosity recommendation chart.

 

[MadScientistMat]

I once tried to ask the Lucas reps at PRI (you'd figure they at least would have some product training) what exactly that oil-climbing-the-gears demo Lucas puts in every parts store is meant to demonstrate. Their responses left me feeling like I'd asked Nigel Tuffnel why he didn't just make 10 louder.