Oil pressure at idle - The 1947 - Present Chevrolet & GMC Truck Message Board Network

jdhcth · 02-10-2007, 03:04 PM

I have a 283 that I just rebuilt and put all new goods in it, oil pump included. At idle I'm gettin' about 20PSI. This seems low to me. At cruising speeds it runs in the high 40s. Does anyone know what ranges I should be seeing. I know I'm runnin' high RPMs on the freeway, 3 speed Saginaw with (at my estimate) a 3.73 gearing.

Speaking of gearing, In 3rd at 65 I'm doing about 3200 RPMs. I have 31" tires. I did the one tire rotation and marked the driveshaft. Came up like 3.73. With stock diameter tires wouldn't this be in the 4s? Say 4.11 or so?

Thanks,
JD

**WorkinLonghorn** · 02-10-2007, 03:24 PM

That sounds fine to me. In the "Truck Data Book" from 1969 it says (for the small blocks) "Normal pressure (psi): 30@ 1170-1200 RPM"
I've seen other sources say 10 lbs per 1000 RPM,and yet others say other things,but 20 at idle is real good imo.

**WorkinLonghorn** · 02-10-2007, 03:30 PM

BTW,I've got 3.73 gears and 31" tires(235/85/16s) and in high gear I'm doing 60 at 2500 RPM and 75 at 3100 RPM.If you had 4.11s you would be 2755 at 60.

centsless · 02-10-2007, 03:44 PM

The newer engines do not even have a spec for idle pressures. They only test them at 1500-2000 rpm. I believe that the oil pressure lights come on when pressures get below 3 psi. The pressures you are getting sound fine to me. My 283 runs about 15-20 psi cold idling and about 45 psi cruising at 50 mph.

jdhcth · 02-11-2007, 11:07 AM

Thanks guys. My tach reads about 3200 at 65 and like I said, that's with 31" tires in 3rd! Maybe my tach's not reading right but I did get around 3.75 driveshaft rotations per one tire rotation. Now with standard diameter tires this ratio would go up but it sounds like lower gear than even 4.11?????

What where the standard gear ratios offered in 67 on the LWB, 3-speed Sag with the 283?

**WorkinLonghorn** · 02-11-2007, 10:20 PM

Quote:

What where the standard gear ratios offered in 67 on the LWB, 3-speed Sag with the 283?

I don't know but I have a tach that reads way too high. They did make a lower gear than 4.10 but you would definitely be buzzing at 75 or even 65.
Check the ratio again carefully (turn the wheel and multiply the DS revs by 2 with an open diff.and one wheel stationary). Temporarily hook up a shop tach and check your accuracy too.

02-10-2007, 03:04 PM	#1
jdhcth Registered User Join Date: Dec 2005 Location: Houston, TX Posts: 51	Oil pressure at idle I have a 283 that I just rebuilt and put all new goods in it, oil pump included. At idle I'm gettin' about 20PSI. This seems low to me. At cruising speeds it runs in the high 40s. Does anyone know what ranges I should be seeing. I know I'm runnin' high RPMs on the freeway, 3 speed Saginaw with (at my estimate) a 3.73 gearing. Speaking of gearing, In 3rd at 65 I'm doing about 3200 RPMs. I have 31" tires. I did the one tire rotation and marked the driveshaft. Came up like 3.73. With stock diameter tires wouldn't this be in the 4s? Say 4.11 or so? Thanks, JD

02-10-2007, 03:24 PM	#2
WorkinLonghorn Senior Member Join Date: Dec 2006 Location: Studio City, Calif. Posts: 2,883	Re: Oil pressure at idle That sounds fine to me. In the "Truck Data Book" from 1969 it says (for the small blocks) "Normal pressure (psi): 30@ 1170-1200 RPM" I've seen other sources say 10 lbs per 1000 RPM,and yet others say other things,but 20 at idle is real good imo. __________________ '69 GMC C2500 Custom Camper, 8 1/2' bed, New GM 350, NP 435 Close Ratio 4spd. Trans., 3.73 Dana-60 open.Camper and Trailer wiring, PS, PB, AC, tach , three gas tanks, stereo speakers, 2nd owner, Work-Truck supreme.

02-10-2007, 03:30 PM	#3
WorkinLonghorn Senior Member Join Date: Dec 2006 Location: Studio City, Calif. Posts: 2,883	Re: Oil pressure at idle BTW,I've got 3.73 gears and 31" tires(235/85/16s) and in high gear I'm doing 60 at 2500 RPM and 75 at 3100 RPM.If you had 4.11s you would be 2755 at 60. __________________ '69 GMC C2500 Custom Camper, 8 1/2' bed, New GM 350, NP 435 Close Ratio 4spd. Trans., 3.73 Dana-60 open.Camper and Trailer wiring, PS, PB, AC, tach , three gas tanks, stereo speakers, 2nd owner, Work-Truck supreme.

02-10-2007, 03:44 PM	#4
centsless sufficiently talented fool Join Date: Jun 2006 Location: Forest Hill, MD Posts: 2,231	Re: Oil pressure at idle The newer engines do not even have a spec for idle pressures. They only test them at 1500-2000 rpm. I believe that the oil pressure lights come on when pressures get below 3 psi. The pressures you are getting sound fine to me. My 283 runs about 15-20 psi cold idling and about 45 psi cruising at 50 mph. __________________ "it's impossible to be surrounded by idiots when you are part of the circle" 2003 Suburban 2002 Pontiac Montana 1981 Corvette 1966 Impala Convertible Click here to support the board

02-11-2007, 11:07 AM	#5
jdhcth Registered User Join Date: Dec 2005 Location: Houston, TX Posts: 51	Re: Oil pressure at idle and gear ratio Thanks guys. My tach reads about 3200 at 65 and like I said, that's with 31" tires in 3rd! Maybe my tach's not reading right but I did get around 3.75 driveshaft rotations per one tire rotation. Now with standard diameter tires this ratio would go up but it sounds like lower gear than even 4.11????? What where the standard gear ratios offered in 67 on the LWB, 3-speed Sag with the 283?



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