Oil Pressure Reading - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Blue Beard · 02-11-2003, 11:03 PM

Any ideas on why the oil pressure pegs the needle on start up?

Using the stock gauges at the moment.

Just changed oil and filter, in case there was a possible problem. Was awful black.

After initial warm up it still shows about 3/4 on the gauge.

Don't know if the engine has had work on it or not.

Appears to be the stock 350 that was stock.......

RUDEDAWG · 02-11-2003, 11:10 PM

What weight oil did you use

Blue Beard · 02-11-2003, 11:20 PM

Don't know what was in it before the change.........

I use Valvoline 10-40 in everything I drive......

Before and after the oil change the readings are the same.........

cableguy0 · 02-11-2003, 11:23 PM

u should be happy that u still got oil pressure that that good i dont exactly remember what pressure is when the stock guage is pegged but its good.

crazy longhorn · 02-11-2003, 11:38 PM

the stock guage is pinned on my 79 at about 55-60 psi. It stays pinned till it warms up, then comes back to about 3/4 guage @ idle(in park). The 355 has about 15,000 mi on it, & runs a hi press pump. It doesnt sound like you have any trouble....crazyL

RUDEDAWG · 02-11-2003, 11:42 PM

What weight oil did you use

crazy longhorn · 02-11-2003, 11:54 PM

Mine has 10/40 in it also.....crazyL

RUDEDAWG · 02-11-2003, 11:55 PM

Hmm. sounds like either you have a high volume pump or you are running too thick of oil. I have the same problem but I am running a high volume pump and 10w30, the average temp. right now is around 50 degrees where i live. i really dont think this is a problem.

crazy longhorn · 02-12-2003, 12:02 AM

No sir, its a high pressure pump(Z 28 replacement), temps are also a little cooler here in Ill. I have a high vol high pressure pump on the longhorn(melling 10555) that will pin a 80 psi guage when its cold......holds 40psi hot @ idle in park, & runs 70 psi @ 3000 rpms hot......crazyL

ChevLoRay · 02-12-2003, 12:14 PM

As long as you have 10 psi per 1000rpm's, you're doing good. Anything else is a "gimmee". My guess is that unless your oil pressure is so high that you are losing oil filters (which might happen with cheap ones), then you have no problem. If it makes you feel any better, my oil pressure is at the upper limit of the guage, when it is cold. As it warms up, it drops. When the engine is hot, at idle, the oil pressure is about 10psi. RPM's are at about 650, so I am okay.

If your oil pressure goes UP, when you let off of the gas, you are seeing an indicator of wear in the main bearings. Otherwise, drive it like it belongs to someone else.

gman · 02-12-2003, 01:13 PM

Well, thats a bit of a relief. I had the same question as Blue Beard. Mine goes to just past the 3/4 line at startup and gradually comes back down to a lit above half after warm up but I felt like I must have problems. High oil pressure is OK from what I've read here. My motor has high mileage but runs quite well. Oil isn't excessively dirty at changes. Using 10w-30. Does thicker or thinner oil help keep pressures up?

crazy longhorn · 02-12-2003, 02:30 PM

Gman, your pressure sound fine for a stocker with some miles on it. I run 20/50 in my 383 in the hot part of the season, & 10/40 in the cooler months . The pressure seems to run about 5 psi higher with 20/50 in the hot weather, as compaired to the 10/40. CrazyL

stelth2002 · 02-12-2003, 03:56 PM

A stock calibrated gauge is suppose to reach 60 psi for everything except the big block. Big block equipped trucks came with an 80 psi gauge. As far as having that much oil pressure, the more the better to a point. It takes power to push all that oil thru and as people have said. 15 psi per 1k rpm is fine with conventional oil and 10 psi with syn. At least thats what i think

72CustomCamper · 02-12-2003, 05:14 PM

Just a some thoughts for everyone:

When your BODY has high blood pressure, it is a sign that your blood is too thick or there are potential clogs.

The variable displacement, gear type pumps in our engines work under the same principle.

1. Thicker oil gives higher pressure.
2. As the oil warms, it becomes less viscous, therefore thinner.
3. Your oil pressure should vary with RPM like stated above since the pump speed and flow rate is roughly proportional to crankshaft speed.
4. Nominal oil pressure for BB's is 40psi. It drops slightly at idle and should never really be above 60psi at any RPM.
5. An engine with considerable sludge buildup will indicate higher pressure than a clean one with the same pump.

The higher pressure is an indication that your pump is working properly but fighting harder to move the oil throughout the ports due to higher viscosity and/or flow barriers.

BOTTOM LINE:
As long as you have pressure, you are good to go.
(that is why there is no redline for oil pressure...)

02-11-2003, 11:03 PM	#1
Blue Beard Registered User Join Date: Jan 2003 Location: Washington State Posts: 8,834	Oil Pressure Reading Any ideas on why the oil pressure pegs the needle on start up? Using the stock gauges at the moment. Just changed oil and filter, in case there was a possible problem. Was awful black. After initial warm up it still shows about 3/4 on the gauge. Don't know if the engine has had work on it or not. Appears to be the stock 350 that was stock....... __________________ 1970 Chev CST 2003 Harley Fatboy 1975 Chevrolet Step Van 1956 Chev Bel Air 1977 Blazer 2WD For Sale $3000.00 1978 Blazer 2WD For Sale $7000.00 1978 Silverado 2005 Monte Carlo

02-11-2003, 11:10 PM	#2
RUDEDAWG Registered User Join Date: Jan 2003 Location: New Mexico Posts: 88	What weight oil did you use __________________ '72 1/2 ton short box 468 BB forged crank/rods/pistons full roller. Msd 6 AL ignition turbo 400 tci. 2800 verter ladderbar/coil rear with currie built ford 9'' rear, 4.11 gears custom built rear frame tubbed, 33/19.50/15 rear m/t. m/t skinnies in front still under construction

02-11-2003, 11:20 PM	#3
Blue Beard Registered User Join Date: Jan 2003 Location: Washington State Posts: 8,834	Don't know what was in it before the change......... I use Valvoline 10-40 in everything I drive...... Before and after the oil change the readings are the same......... __________________ 1970 Chev CST 2003 Harley Fatboy 1975 Chevrolet Step Van 1956 Chev Bel Air 1977 Blazer 2WD For Sale $3000.00 1978 Blazer 2WD For Sale $7000.00 1978 Silverado 2005 Monte Carlo

02-11-2003, 11:23 PM	#4
cableguy0 Senior Member Join Date: Apr 2000 Location: Delta,Pa Posts: 14,950	u should be happy that u still got oil pressure that that good i dont exactly remember what pressure is when the stock guage is pegged but its good. __________________ Owner of North Point Car Care in Dundalk Md. We specialize in custom exhaust on both modern and classic vehicles. We are a full service auto shop from classics to modern vehicles. Feel free to contact me with questions. I will give a 10% discount to any board member.

02-11-2003, 11:38 PM	#5
crazy longhorn Fabricate till you "puke" Join Date: Jun 2002 Location: Ill Posts: 9,403	the stock guage is pinned on my 79 at about 55-60 psi. It stays pinned till it warms up, then comes back to about 3/4 guage @ idle(in park). The 355 has about 15,000 mi on it, & runs a hi press pump. It doesnt sound like you have any trouble....crazyL __________________ 69 longhorn,4" chop,3/5 drop, 1/2 ton suspension/disc brakes,1 1/2" body drop,steel tilt clip, 5.3/Edelbrock rpm intake/600 carb, Hooker streetrod shorties,2 1/2" exhaust/ H pipe/50's Flows , 6 spd Richmond trans,12 bolt/ 3.40 gears....

02-11-2003, 11:42 PM	#6
RUDEDAWG Registered User Join Date: Jan 2003 Location: New Mexico Posts: 88	What weight oil did you use __________________ '72 1/2 ton short box 468 BB forged crank/rods/pistons full roller. Msd 6 AL ignition turbo 400 tci. 2800 verter ladderbar/coil rear with currie built ford 9'' rear, 4.11 gears custom built rear frame tubbed, 33/19.50/15 rear m/t. m/t skinnies in front still under construction

02-11-2003, 11:54 PM	#7
crazy longhorn Fabricate till you "puke" Join Date: Jun 2002 Location: Ill Posts: 9,403	Mine has 10/40 in it also.....crazyL __________________ 69 longhorn,4" chop,3/5 drop, 1/2 ton suspension/disc brakes,1 1/2" body drop,steel tilt clip, 5.3/Edelbrock rpm intake/600 carb, Hooker streetrod shorties,2 1/2" exhaust/ H pipe/50's Flows , 6 spd Richmond trans,12 bolt/ 3.40 gears....

02-11-2003, 11:55 PM	#8
RUDEDAWG Registered User Join Date: Jan 2003 Location: New Mexico Posts: 88	Hmm. sounds like either you have a high volume pump or you are running too thick of oil. I have the same problem but I am running a high volume pump and 10w30, the average temp. right now is around 50 degrees where i live. i really dont think this is a problem. __________________ '72 1/2 ton short box 468 BB forged crank/rods/pistons full roller. Msd 6 AL ignition turbo 400 tci. 2800 verter ladderbar/coil rear with currie built ford 9'' rear, 4.11 gears custom built rear frame tubbed, 33/19.50/15 rear m/t. m/t skinnies in front still under construction

02-12-2003, 12:02 AM	#9
crazy longhorn Fabricate till you "puke" Join Date: Jun 2002 Location: Ill Posts: 9,403	No sir, its a high pressure pump(Z 28 replacement), temps are also a little cooler here in Ill. I have a high vol high pressure pump on the longhorn(melling 10555) that will pin a 80 psi guage when its cold......holds 40psi hot @ idle in park, & runs 70 psi @ 3000 rpms hot......crazyL __________________ 69 longhorn,4" chop,3/5 drop, 1/2 ton suspension/disc brakes,1 1/2" body drop,steel tilt clip, 5.3/Edelbrock rpm intake/600 carb, Hooker streetrod shorties,2 1/2" exhaust/ H pipe/50's Flows , 6 spd Richmond trans,12 bolt/ 3.40 gears....

02-12-2003, 12:14 PM	#10
ChevLoRay Old Skool Club Join Date: Jun 2001 Location: Benton, AR "The Heart of Arkansas" Posts: 10,880	10PSI/1000RPM's As long as you have 10 psi per 1000rpm's, you're doing good. Anything else is a "gimmee". My guess is that unless your oil pressure is so high that you are losing oil filters (which might happen with cheap ones), then you have no problem. If it makes you feel any better, my oil pressure is at the upper limit of the guage, when it is cold. As it warms up, it drops. When the engine is hot, at idle, the oil pressure is about 10psi. RPM's are at about 650, so I am okay. If your oil pressure goes UP, when you let off of the gas, you are seeing an indicator of wear in the main bearings. Otherwise, drive it like it belongs to someone else. __________________ Member Nr. 2770 '96 GMC Sportside; 4.3/SLT - Daily driven....constantly needs washed. '69 C-10 SWB; 350/TH400 - in limbo The older I get, the better I was.

02-12-2003, 01:13 PM	#11
gman Registered User Join Date: Nov 2000 Location: Ogden, Utah Posts: 290	Well, thats a bit of a relief. I had the same question as Blue Beard. Mine goes to just past the 3/4 line at startup and gradually comes back down to a lit above half after warm up but I felt like I must have problems. High oil pressure is OK from what I've read here. My motor has high mileage but runs quite well. Oil isn't excessively dirty at changes. Using 10w-30. Does thicker or thinner oil help keep pressures up? __________________ 72 Chevy SWB Custom Deluxe K10, 350/SM465, PS, PB, Fact. Air 2000 Harley...Wide Glide

02-12-2003, 02:30 PM	#12
crazy longhorn Fabricate till you "puke" Join Date: Jun 2002 Location: Ill Posts: 9,403	Gman, your pressure sound fine for a stocker with some miles on it. I run 20/50 in my 383 in the hot part of the season, & 10/40 in the cooler months . The pressure seems to run about 5 psi higher with 20/50 in the hot weather, as compaired to the 10/40. CrazyL __________________ 69 longhorn,4" chop,3/5 drop, 1/2 ton suspension/disc brakes,1 1/2" body drop,steel tilt clip, 5.3/Edelbrock rpm intake/600 carb, Hooker streetrod shorties,2 1/2" exhaust/ H pipe/50's Flows , 6 spd Richmond trans,12 bolt/ 3.40 gears....

02-12-2003, 03:56 PM	#13
stelth2002 Young Gun wth Fast Inline Join Date: Jan 2002 Location: Idaho Posts: 1,475	A stock calibrated gauge is suppose to reach 60 psi for everything except the big block. Big block equipped trucks came with an 80 psi gauge. As far as having that much oil pressure, the more the better to a point. It takes power to push all that oil thru and as people have said. 15 psi per 1k rpm is fine with conventional oil and 10 psi with syn. At least thats what i think __________________ 1967 Chevrolet LWB with built 292! 415 ft. lbs of torque, 4 speed :O with 27% overdrive too, 3.73 Posi. Frame and body done... getting painted!!!

02-12-2003, 05:14 PM	#14
72CustomCamper Registered User Join Date: Feb 2003 Location: Bremerton, WA Posts: 86	Just a some thoughts for everyone: When your BODY has high blood pressure, it is a sign that your blood is too thick or there are potential clogs. The variable displacement, gear type pumps in our engines work under the same principle. 1. Thicker oil gives higher pressure. 2. As the oil warms, it becomes less viscous, therefore thinner. 3. Your oil pressure should vary with RPM like stated above since the pump speed and flow rate is roughly proportional to crankshaft speed. 4. Nominal oil pressure for BB's is 40psi. It drops slightly at idle and should never really be above 60psi at any RPM. 5. An engine with considerable sludge buildup will indicate higher pressure than a clean one with the same pump. The higher pressure is an indication that your pump is working properly but fighting harder to move the oil throughout the ports due to higher viscosity and/or flow barriers. BOTTOM LINE: As long as you have pressure, you are good to go. (that is why there is no redline for oil pressure...) __________________ '72 GMC C20, "2500 Super Custom", Custom Camper, New 454 '93 K2500 Suburban, Old 454 (157K)



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