oil pressure question

[BarryK]

Hi

I've been finding that at idle my oil pressure seems a bit low. When at idle the gauge would vary at times between barely above the 0 lbs to up to maybe around 10 or 15 lbs of pressure. When actually driving down the road it would go up to around 60 lbs but drop back to very low pressure at idle when i'm stopped at lights, etc.
I'm also burning through oil fairly quickly in the motor. approx 1 or 1 1/2 quarts every 500 miles or so. it's hard to know just the true milage as my odometer doesn't work but i'm only driving the car locally and haven't been on any long highway cruises lately - only around town so the milage shouldn't be that high between adding oil.
I discussed this with my neighbor who has a '67 BB and does his own work on his car and has been helping me out and he suggesting adding a different weight oil to help my pressure problem. He recommended using a 20W50 weight. He actually uses that weight as his regular, routine oil.
This morning I checked the oil and was down again so I added 1 1/2 quarts of the 20w50 for the first time. immediately my pressure at idle jumped up and it's now sitting at just a bit over 40lbs at idle but if I rev past approx 2500rpm's the pressure jumps to 80lbs or more. The gauge only reads up to 80lbs but now it's pegging the gauge and looks like it's going beyond the 80lbs.
Is this pressure above idle too high and something to be concerned about?

I know too little oil pressure is a major concern, but can you actually get too much pressure in the system also?

[Tempus_Fugit]

Rule of thumb is 10psi/1000rpm so 2000 rpm would give 20psi oil press. My 365 runs about like this. I wonder if your gauge is not a little sticky.

Consumption problems usually have little to do with oil pressure.

Valve guide seals get hard on old chevys and give you smoke on cold startip. Bad rings will put oil in the air cleaner. Also make sure the orifice in the crank case vent at the carb is not plugged.

John

Originally Posted by BarryK

Hi

I've been finding that at idle my oil pressure seems a bit low. When at idle the gauge would vary at times between barely above the 0 lbs to up to maybe around 10 or 15 lbs of pressure. When actually driving down the road it would go up to around 60 lbs but drop back to very low pressure at idle when i'm stopped at lights, etc.
I'm also burning through oil fairly quickly in the motor. approx 1 or 1 1/2 quarts every 500 miles or so. it's hard to know just the true milage as my odometer doesn't work but i'm only driving the car locally and haven't been on any long highway cruises lately - only around town so the milage shouldn't be that high between adding oil.
I discussed this with my neighbor who has a '67 BB and does his own work on his car and has been helping me out and he suggesting adding a different weight oil to help my pressure problem. He recommended using a 20W50 weight. He actually uses that weight as his regular, routine oil.
This morning I checked the oil and was down again so I added 1 1/2 quarts of the 20w50 for the first time. immediately my pressure at idle jumped up and it's now sitting at just a bit over 40lbs at idle but if I rev past approx 2500rpm's the pressure jumps to 80lbs or more. The gauge only reads up to 80lbs but now it's pegging the gauge and looks like it's going beyond the 80lbs.
Is this pressure above idle too high and something to be concerned about?

I know too little oil pressure is a major concern, but can you actually get too much pressure in the system also?

[grumpyvette]

things you might want to read

link 1

link 2

link 3

http://www.scuderiaciriani.com/rx7/oil_filter_study/

[BarryK]

Originally Posted by Tempus_Fugit

Rule of thumb is 10psi/1000rpm so 2000 rpm would give 20psi oil press. My 365 runs about like this. I wonder if your gauge is not a little sticky.

Consumption problems usually have little to do with oil pressure.

Valve guide seals get hard on old chevys and give you smoke on cold startip. Bad rings will put oil in the air cleaner. Also make sure the orifice in the crank case vent at the carb is not plugged.

John

well, at idle (about 700-800rpm) the pressure was barely above 0 and that is what initally was concerning me. The gauge didn't "seem" sticky. As i increased RPM's the gauge would climb steadily up without seeming to act sticky or move up in jumps. My major concern is now the pressure at driving RPM's seems high.

On cold start-up I'm not seeing any smoke but the oil in the air cleaner indicating bad rings now has me concerned!


I have made sure the small hole in the 90 degree brass fitting on the side of the carb is clear. JohnZ told me about that one a few weeks ago.

[BarryK]

thanks grumpy for the informative links.

plenty of that is still well above my head but i'm going to try to read it in more detail later today and try to understand more of it.

[allcoupedup]

Barry,

I think you should buy an oil pressure gauge and a compression tester. The oil pressure gauge can be connected to the front of the block quite easily. I wouldn't chase low oil pressure until I could confirm the in-dash gauge readings.

Compression tester will tell you if your rings are in need of attention.
Brian

[BarryK]

Hi Brian

my neighbor has a compression tester and we are going to check for compression and leak-down on each cylinder. I REALLY hope it's not the rings as I'm not up to paying for a complete motor rebuild yet!

My mechanic has an oil pressure gauge he said we can hook up to check actual pressure to compare against the gauge reading. He already checked for me and said the listed "spec's" on that motor was 40lbs at 2000rpm's. i'm pretty much getting that, it's only at obsolute idle when it drops to almost 0 that has me worried.
Although it shot up this morning at idle, now that I drove it a while and the motor got nice and warm, the idle pressure went back down to where it was before - barely above idle.

[Sky65]

I agree. Oil pressure and oil consuption are two differant issues.
Oil pressure

• Definitely verify the oil presure with an other gauge.
• What oil weight are you using?

Oil consuption

• If you are burning 1-1 1/2 qts in 500 miles I would expect you would see evedence on the plugs.
• If this has been an issue since the engine was rebuilt maybe you have the wrong dipstick or dipstick tube. If you overfill the engine it will likely burn off the overfill quickly looking like a consumption problem.

[Tempus_Fugit]

To check rings with a compression gauge you need to do a compression check, then squirt a little oil into the cylinder and see if the reading changes significantly, maybe 10% or so. A car with worn out rings might give you 120 psi comp at first, then 160 after oil is added.

Also, if the breather (the big tube from the back of the block to the air cleaner is going puff-puff-puff at idle, you definitely have a ring problem. My friends 300hp '64 was puffing big time, on disassembly, two of the pistons had cracked rings.

John

Originally Posted by BarryK

Hi Brian

my neighbor has a compression tester and we are going to check for compression and leak-down on each cylinder. I REALLY hope it's not the rings as I'm not up to paying for a complete motor rebuild yet!

My mechanic has an oil pressure gauge he said we can hook up to check actual pressure to compare against the gauge reading. He already checked for me and said the listed "spec's" on that motor was 40lbs at 2000rpm's. i'm pretty much getting that, it's only at obsolute idle when it drops to almost 0 that has me worried.
Although it shot up this morning at idle, now that I drove it a while and the motor got nice and warm, the idle pressure went back down to where it was before - barely above idle.

[BarryK]

Originally Posted by Sky65

I agree. Oil pressure and oil consuption are two differant issues.
Oil pressure

• Definitely verify the oil presure with an other gauge.
• What oil weight are you using?

Oil consuption

• If you are burning 1-1 1/2 qts in 500 miles I would expect you would see evedence on the plugs.
• If this has been an issue since the engine was rebuilt maybe you have the wrong dipstick or dipstick tube. If you overfill the engine it will likely burn off the overfill quickly looking like a consumption problem.

Hi Sky

I'm going to get the car to my mechanic soon to check the actual pressure with his gauge instead of the gauge in the dash.
As for oil weight, I don't know what my last mechanic put in when he changed the oil and filter last when I had him adjust the valves but my neighbor suggested going to a 20W50 so that's what I added in this morning.

My neighbor pluugedthe 31 plug last week to look at it. We thought it looked a bit too much on the black color side - he said the tip should be more of a tan color if the car was burning everything correctly. Would black be the misture was too rich on the carb? it wasn't gunked up or dripping oil or anything like that and it's didn't have any carbon or powder like residue - it actually looked pretty decent just maybe too black. If it matters, the plugs were all changed approx 500 miles ago with AC45's.

How would I be able to tell if I have the wrong dipstick or dipstick tube??

[Sky65]

The owners manual for my 65 calls for 10W30 for temps above 0 deg F. Please note I have not checked the accuracy of my gauge but that is what I am using and the gauge reads 30-35 lbs at idle hot. Also I am using petroleum based oil, not synthetic. All I am saying is if don't know what oil is in the engine, an oil change is alot easier and less expensive than an engine tear down. If it was mine I would want to know it is correct before going any further. Same goes for an external gauge reading.

As far as the dipstick I'm affraid I do not know the correct deminsions. My car has a later model 350 and I don't know if they are the same. I only know an over filled engine can consume oil quicker than a properly serviced one. Also, I have seen differant part number dipsticks listed in parts books for differant gm engines. It is worth a check. I'd bet there is another forum member that knows the correct dipstick length.

I am speaking from some automotive experiance and little bit of logic. I am not a gm expert by any stretch but I have seen many a tech go deep into a repair without checking the basics only to find the simple answer end.

Sky

[myonnone]

Barry,

I had a very low oil pressure situation much like yours when I first purchased my 66. I did the requisite compression check. All was ok. I then decided to put a new oil pump in. That fixed it. It was a simple job and I did it with just putting the car up on jackstands.

[BarryK]

hi My

i'm not ready to do the oil pump yet, too many other things to check first such as the compression and leakdown tests.

for curiousity sake though, how hard is repalcing the oil pump? I assume it's "inside" and it involves having to drop the oilpan? Is it as simple as draining the oil, dropping the pan, unbolting the old pump and bolting in the new and putting the pan back on?

Barry

[grumpyvette]

"Is it as simple as draining the oil, dropping the pan, unbolting the old pump and bolting in the new and putting the pan back on?"

YES AND NO! MOSTLY NO!

yes you drop the pan and install a new pump, but you MUST BRAZE the pickup to the pump AFTER first making sure the pump pickup is correctly possitioned to sit 1/2" MAX to 3/8" min from the oil pan floor , or you have a good chance of it coming loose eventually due to vibration,and you must remove the spring from the oil bye-pass circuit in the pump and replace it after the pump cools, you should make pre-priming the pump much easier by putting some moly grease on the gears before re-assembling the pump. adding a BRACE between the pump body and the pick up is a smart move also.
fill the new oil filter with oil and the pan to the correct level and THEN turn the engine over with the starter without the coil connected untill the gauge reads pressure before starting the engine.
its a good time to use a one piece synthetic oil pan gasket and replace the bolts with studs also. keep in mind a oil pump is only PART of the oil system and getting the oil back to the pan quickly is a good idea, so a windage screen, and a HIGH voluum BAFFLED oil pan is a great idea you might want to add at that time instead of just replacing the stock pan which is FAR from ideal for high rpm performance use!!


things you might want to read

link 1

link 2

link 3

http://www.scuderiaciriani.com/rx7/oil_filter_study/

[BarryK]

Originally Posted by grumpyvette

"Is it as simple as draining the oil, dropping the pan, unbolting the old pump and bolting in the new and putting the pan back on?"

YES AND NO! MOSTLY NO!

yes you drop the pan and install a new pump, but you MUST BRAZE the pickup to the pump AFTER first making sure the pump pickup is correctly possitioned to sit 1/2" MAX to 3/8" min from the oil pan floor , or you have a good chance of it coming loose eventually due to vibration,and you must remove the spring from the oil bye-pass circuit in the pump and replace it after the pump cools, you should make pre-priming the pump much easier by putting some moly grease on the gears before re-assembling the pump. adding a BRACE between the pump body and the pick up is a smart move also.
fill the new oil filter with oil and the pan to the correct level and THEN turn the engine over with the starter without the coil connected untill the gauge reads pressure before starting the engine.
its a good time to use a one piece synthetic oil pan gasket and replace the bolts with studs also. keep in mind a oil pump is only PART of the oil system and getting the oil back to the pan quickly is a good idea, so a windage screen, and a HIGH voluum BAFFLED oil pan is a great idea you might want to add at that time instead of just replacing the stock pan which is FAR from ideal for high rpm performance use!!


things you might want to read

link 1

link 2

link 3

http://www.scuderiaciriani.com/rx7/oil_filter_study/

ok than.....way out of MY league for repair work!
if it comes to an oil pump replacement it will go into my mechanic.