Oil Pressure Conundrum?

SmokinBBC

SmokinBBC

Well-known member
Joined
Mar 25, 2008
Messages
2,730
Location
Oak Ridge, NC
My pressure at operating temp has always been consistent. around 35 at idle and reaching 65 at cruise and almost 70 at WOT. When cold it would be about 65 and then drop to 35 at idle (approx 700RPM). Measured with the stock gauge.

Within the last few months idle pressure has steadily dropped to about 20. However cruise and WOT are still the same. Raising the idle to about 850 will get me back to 35psi...idle is at 700RPM to eliminate run on.

Could the tolerances have opened up this quickly? On an older engine I would be ok with this but on an 8000mile engine, I'm a little concerned about such a drop at idle over a couple of months(maybe 1500 to 2000 miles driven).

What say you?


Some more info:
454 close to 490crank HP (hyd roller) ..manual trans
10w30 Royal P. K$N (I know....overkill) since 2000 miles on the engine
Melling Oil Pump...most like HV based on the pressure but not entirely sure.
No engine knocks, noises, lifter noise
Very little oil consumption. No leaks.
No metal in the oil or on metallic plug (just changed the oil again and still have the filter...may cut it open)
No loss of power.
No pressure drops during spirited driving or WOT.
No overheating
Operating Engine temp=195
Operating oil temp =220 measured at the lower part of the pan.
Holds 5qts +1/2qt in the filter


I did have severe engine flooding last summer, but did not drive it until after I changed the oil.
 
Don't have any answers for you but it does sound like an abrupt change. How soon after the flooding did the pressure start to change?
 
It starting to drop a little by little about a month or 2 after. The oil level did not increase and it doesn't burn any oil.

What gets me is that pressure while driving is the same as it was...only drops at idle.
 
I think it's fine, had many a engine like that, the SBC in the motor home runs 40 at speed, and 20 at idle.....

quite as a mouse...:yahoo:
 
mrvette said:
I think it's fine, had many a engine like that, the SBC in the motor home runs 40 at speed, and 20 at idle.....

quite as a mouse...:yahoo:
Click to expand...

I am going to pull the filter to make sure there isn't anything up with the bypass.

I looked down the 710 hole in the valve cover and there was plenty of oil streaming at idle.

I think I'll leave it and just keep an eye on it for now....perhaps a pressure leak in the lifter bore....cam bearings, etc.

Thanks for the input!
 
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