slant 6 oil pressure

[suavecito80]

My slant 6 was rebuilt. Supposely they install all new guts..like main bearings, journals etc. This is my second oil pump install. my pressures are like 20 psi high idle. low idle 12 psi. I installed a manual oil gauge. Can somebody let me know if these pressures are good? My truck is a 1980 dodge D150. I currently have like 60 miles. I did a new oil change put in 10w-30 in hopes to get rid of any new part debri or slush.

 

[DodgeLad]

My 1980 /6 truck sits just under halfway on the gauge. I think that's around 30psi or so? Your pressures are within spec, but on a new motor I would wonder too.

 

[nm9stheham]

DodgeLad, what weight oil are you running? For an older engine and if built with wider clearances or with factors like the crank journals being a bit worn and rebuilt with bearing clearances at the service limits, 10W30 seems a bit lightweight. 10W40 was pretty commonly used in the day when these were production engines.

I would try some 10w40 and see what you get. It would not surprise me if the crank journals were not turned down to the next underszie and you have loose beaing clearances.

 

[pishta]

Your good unless it drops to under 6 @ idle. You are not floating the bearings, only pressurizing them, they 'roll' over the oil layer. rule of thumb: 10 psi per 1000 rpm. oil pressure is misunderstood, the more you have, the more your motor is taxed on pumping it.

 

[BillGrissom]

I second pista's explanation. The oil pump need only provide oil volume flow to the bearings. The bearing spinning generates the pressure to support the crankshaft (and rods). Trains had the first journal bearings (halves) and didn't even have an oil pump, the axle ran in a tub of oil and dragged the oil up into the bearing. It was many years before engineers figured out how it actually worked. One guy measured >1000 psi as the train rolled.

Still, if the oil pump is moving the specified volume, the pressure results from the bearing gaps. 20 psi sounds low for a newly rebuilt engine. I would expect >40 psi at idle.

 

[Darter6]

My 2010 chevy motorhome 6.0 LS engine, since new, has about 10 psi at hot idle and 28 psi running down the road. Factory spec 5-30 oil. Sounds like your engine was built a little loose.You should be ok. Next oil change try 15-40.

 

[DodgeLad]

DodgeLad, what weight oil are you running? For an older engine and if built with wider clearances or with factors like the crank journals being a bit worn and rebuilt with bearing clearances at the service limits, 10W30 seems a bit lightweight. 10W40 was pretty commonly used in the day when these were production engines.

I would try some 10w40 and see what you get. It would not surprise me if the crank journals were not turned down to the next underszie and you have loose beaing clearances.

I've tried 5w40 Rotella syn. and there is 10w30 in there now. Doesn't seem to make much difference. If there is a difference, it's only a couple psi and I can't discern it on the old gauge.

 

[mcnoople]

My 2010 chevy motorhome 6.0 LS engine, since new, has about 10 psi at hot idle and 28 psi running down the road. Factory spec 5-30 oil. Sounds like your engine was built a little loose.You should be ok. Next oil change try 15-40.

Just putting it out there. In recent years GM has had many issues with their V8 engines. Problems like excessive oil consumption and premature engine failure. I have talked to owners that went through 3 engines in 60K miles. 1 guy noticed his engine burning oil and Gm wouldn't do anything, they told him to add oil as needed. He didn't, it blew up, and they replaced it under warranty.

But more on topic, in my valiants owner manual it says that it okay to have the oil pressure light flicker on dimly if stopped in gear while idling hot. That is a whole 4 psi. My valiant would run 40 psi when running down the road with around 100K on the clock.

 

[nm9stheham]

I've tried 5w40 Rotella syn. and there is 10w30 in there now. Doesn't seem to make much difference. If there is a difference, it's only a couple psi and I can't discern it on the old gauge.

OK, 10W40 non synthetic will tend to have a bit more viscosty than a 5W40 synthetic unless it is really hot. But the thinner oil should flow well.

If I was the OP and worreid about pressure, I would put in a pure synthetic like Mobil 1, maybe a 15W40, and never worry about it again.

 

[nm9stheham]

My slant 6 was rebuilt. Supposely they install all new guts..like main bearings, journals etc. This is my second oil pump install. my pressures are like 20 psi high idle. low idle 12 psi. I installed a manual oil gauge. Can somebody let me know if these pressures are good? My truck is a 1980 dodge D150. I currently have like 60 miles. I did a new oil change put in 10w-30 in hopes to get rid of any new part debri or slush.

What is the pressure at road speed?

 

[RustyRatRod]

What is the pressure at road speed?

This ^^^^^

It should have 10 PSI for every 1000 RPM as has been said. 10 PSI at 1000, 20 at 2000, 30 at 3000. Those would be considered minimums. If it has at least that, it's good.

 

[barbee6043]

my 72 slant duster( unknown mileage and condition),, driving down the road hot, when I got to corner to turn ,,oil light work come on and flicker, put manual gauge in and shows plenty of pressure cold, hot, so the idiot light gauge, maybe the NEW sender doesn't read properly!?? just wondering.....

 

[cjh]

My slant ran 60 psi oil pressure with 20W50 in it, and it was still the same when I used 15W60 in it. At revs, it went to about 65 psi......didn't matter if it was hot or cold.

 

[cjh]

my 72 slant duster( unknown mileage and condition),, driving down the road hot, when I got to corner to turn ,,oil light work come on and flicker, put manual gauge in and shows plenty of pressure cold, hot, so the idiot light gauge, maybe the NEW sender doesn't read properly!?? just wondering.....

Mine would do the same when chucked into a lefthander at speed, so I modified the sump with a baffle/anti-surge plate, and it never did it again.

 

[nm9stheham]

OK, 10W40 non synthetic will tend to have a bit more viscosty than a 5W40 synthetic unless it is really hot. But the thinner oil should flow well.

If I was the OP and worreid about pressure, I would put in a pure synthetic like Mobil 1, maybe a 15W40, and never worry about it again.

OH and BTW, OP, if you do go to synthetic, don't do it right away. Run the engine in the normal break in cycle with non-synthetic 'til around 500 miles or more and then switch. The miles broken in on non-synthetic are neded to make sure the rings seat in properly.

Again, try a 15W40 non-synthetic and see what it does. Your pressures don't sound all that bad if you have some decent pressure at road speed. I would be trying a heavier oil before doing anything else; I just think you wider bearing clearances in the engine after the rebuild, and the older standard oil weights apply.