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]

oil pressure

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

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]

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]

rings

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

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]

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?? :confused

 

[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]

"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.

 

[ctjackster]

If Barry has the correct L76 set-up, he has a big pan and a nice windage tray already.

 

[grumpyvette]

BARRYK
DON,T BE SCARED OFF ON REPLACING THE OIL PUMP JOB!!
ITS a project ANYONE with minimal skills and a few tools can do if you take your time!
it makes for a great first engine project
you can get a local machine shop to braze the pick-up to the pump REALLY cheaply (under $10 or less in most cases) just use some model clay to determine the correct location/clearance in the pan

http://www.melling.com/highvol.html
I would strongly advise useing FOUR QUALITY JACK STANDS on a LEVEL conctrete surface thou!!

I think youll find these very handy if you work on cars and don,t have a lift
BTW the 12 ton stands are PREFERED as they have a MUCH WIDER BASE and EXTRA STRENGTH,(if IM GOING UNDER A CAR I DON,T WANT TO BENCH PRESS THE DAMN THING TO GET OUT FROM UNDER IT)
how much is you LIFE WORTH,BUY THE ! THE 12 ton RATED STANDS they are MUCH MUCH safer than the 3-6 ton stands IF ONLY BECAUSE THEY ARE FAR HARDER TO TIP OVER IF SOMEONE ROCKS THE CAR! and they DON,T need to be extended to give room under the corvette! in fact they are the perfect height at the first notch when you place them on the frame at the 4 corners of the frame
your NOT looking for the LIFT RATING NEARLY as much as the WIDE BASE, and STABILITY plus the extra safety just thier base to height ratio gives

2 Piece Set
These super heavy duty jack stands will hold most cars and trucks safely over 2 feet off the ground. Perfect for repair work or storage.
Height: 19-1/2'' to 30-1/8''
Base: 12'' x 12-1/2''
Weight: 68 lbs.
THIS ABOVE IS RIGHT OFF THE HF WEB SITE
http://www.harborfreight.com/cpi/ctaf/Disp...temnumber=34924
second, thing is IVE used a set of four very similar 12 ton jack stands from NORTHERN TOOL for years, with no problems what so ever

http://www.northerntool.com/webapp/wcs/sto...19&categoryId=0

Torin Pair of 12–Ton Jack Stands
2 heavy–duty steel jack stands at one low price! Double locking pawl and tooth design for extra protection. Minimum height is 18 1/8in. Maximum height is 28in.
In Stock
Ship Wt. 63.0 lbs
Item# 144872
Discount Price... $64.99
Sale Price... $54.99
110% Guaranteed Lowest Price!

youll be getting them at a significant discount if they price match, which they should

 

[BarryK]

Grumpy

well, I'm definetly one that qualifies as having MINIMUM skills and few tools!

I'm don't know what you mean about brazing the pickup on the new pump. Also not sure i understand about the cleaance issue. If it's a replacement pump of the same type why wouldn't it fit on the same as the old pump?

 

[grumpyvette]

the oil pump pick-up on a SB chevy pump is usually a friction fit tube inserted into the pump body with an interfearance fit, it has a tendency to work lose over time if its not brazed (welded) to the pump in HIGH performance applications with their higher than normal vibration levels and stress loads

but before you braze it you must possition the pick-up so its 1/2" from the oil pan floor with the pump and pan installed, this is easily measured by placing modeling CLAY under the pick-up and installing the pan with just the 4 corner bolts to test clearance issues
this is required because the tube can be rotated so that the clearace variers a great deal, if the pickup is closer than about 3/8" it can restrict oil flow, more than about 1/2" clearance and in some extreme cases with low voluum oil pans and it sucks air, if the oil levels low so you need it correctly installed
once you get the pick up installed with 1/2" clearance to the pain floor get it BRAZED in that location to the pump body

 

[BarryK]

Grumpy

thanks for the explanation, it helps me understand it a lot more, but it also comfirmed to me that this seems like a job best suited a mechanic rather than me, at least for now at my level of skills on working on cars. Keep in mind, replacing the temp sending unit was the first thing i've done on my own on this car!
i'll try another simple job next like changing the oil or rotating the tires and work my way up slowly before getting myself anywhere INSIDE the motor at all.

BTW, speaking of simple jobs on the car, or what SHOULD be a simple job, can anyone explain to me GM's reasoning for putting the sparkplug shielding brackets in such an inconvient place right in front and on top of each plug on the SB motors?? My neighbor and I had to pull one of the plugs last week to check it and after removing the shielding it was still very difficult to get the sparkplug socket down in ther and around the bracket! He ended up having to slide the socket on the plug and than use a straight wrench to turn the socket instead of the socket ratchet. On his 427 BB motor the plugs are real easy to access. He said he can have all of his plugs out in 5 minutes - it took him 10 minutes to just the one plug out of my SB!
Sheesh, bad design there.