My Oil prssure drops at idle to 5 - 10 pds. If I increase my RPM it goes up considerably. At cruise speed it is fine. Whats the deal, is it low vacuum at idle. I do not have a radical cam. My cam is an 230/236@50, 487/490 lift with 1.6 rockers. What could be the problem or is this OK

5~10 psi is lower than normal for most engines. You would probably like to see something more like 20~30 psi at idle.
Low oil pressures at Idle are usually due to clearance problems in the motor. These can be from main/rod bearings, cam bearings and/or pump internal clearances.
The Main/Rod bearings can be worn, if long service miles on engine, or the clearances could be above normal or the bearings scratched or damaged if the engine has recently had an overhaul.
The Cam bearings could be worn but this is not often the cause of low pressure in a Chevy. More likely, if the engine has recently been overhauled or the Cam replaced, the bearings may have been scratched or gouged as the cam was installed.
The pump may also be a cause if it has internal clearance problems.
There are a couple of other places that can cause low oil pressures - but they usually show other signs of trouble you haven't mentioned.
Let us know more about the engine, such as rebuild dates and service miles, and we can help you track down the low pressure problem better.

Tommy,
What is 'fine'? Where's the gauge reading when you're driving?
Have you ruled out the gauge\sending unit\hook-ups?

The engine has about 2000k on it. I was comnpletely rebuilt about 3.5 yrs ago. A year ago I changed from 2.02 fuelies to AFR heads. I also replaced the cam when I did this. Below is my build:

Block 350 - .20 over
AFR 195 cc heads milled to 64.1cc
Comp Cam XE 274 (230/236@50) 487/490)
1.6 roller rockers
Edel RPM Air Gap
Holley 650DP
Hooker 1 3/4"
DR Gas X pipe
M20
4:10's
My idle is at 800rpm - Marginal vacuum at this.

Cruising I run at about 25 - 30 pounds. Idle I go down to 5. This just started about two months ago - prior to this she idled at about 15 pds pressure.

I have not checked the guage sending unit.

What are other possibilities?

well with 2000K miles on it, im surprised it still fires up every morning.

sorry, i was trying to be funny... graemlins/sad.gif

I wish I could average 1,566 miles a day on my car! :D

KKK! I ment 2k!

robert, you made me laugh ;) .i would be less concerned (although still concerned) if it was always running pressure like that from the get-go, but since you say it changed recently, that would concern me for sure. any sign of metal in the oil? might try cutting apart your filter and seeing what it has (besides oil) inside. i would start looking for something, anytime oil pressure changes from it's norm (unless a change such as thinner oil has been made) is reason for concern, imo. definately try another gauge just to support your readings, though. good luck with it

You guys are scaring me now. Thanks for the advice - I will keep you posted.

might be a long shot, but could it be that the change in cylinder head material (iron to aluminum) has changed the amount of heat being put into the oil, thus making the oil operate at a higher temperature and as such thinning it out?

Could also be a bad sender, gauge, or wiring problem.

tommyg
What grade of oil are you using?? Performance engines are usually built with a little more clearance than a factory engine. Combine this with a slightly inaccurate oil pressure gauge and you could get a low gauge reading. Try a 20W-50 oil (if you haven't already) and see what happens. Also, you could try a mechanical oil pressure gauge to see if yours is correct.
Just some thoughts
Jim

I use straight 30 weight.

Originally posted by GMJim:
tommyg
What grade of oil are you using?? Performance engines are usually built with a little more clearance than a factory engine. Combine this with a slightly inaccurate oil pressure gauge and you could get a low gauge reading. Try a 20W-50 oil (if you haven't already) and see what happens. Also, you could try a mechanical oil pressure gauge to see if yours is correct.
Just some thoughts
Jim Also, you could try a mechanical oil pressure gauge to see if yours is correct.


Thats my best suggestion,too,
get a mechanical gauge,thats what i am using,
and i see 25+lbs at idle,warm
and 40+ when cruising;when cold,first starting up
its about 55 lbs.