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

Lobo'74 · 08-25-2003, 11:24 PM

The engine in my '67 is a '79 350 that was rebuilt by the previous owner to the following specs:

*350, 4 bolt mains
*Bored .030 over
*Align Bored
*Parallel top of block
*New Cam bearings
*New freeze plugs
*New hypereutecic pistons, flat top
*Reconditioned connecting rods
*Crankshaft main and rod journals ground .010 under
*rotating assembly balanced
*Double roller timing chain
*Melling high volume, high pressure oil pump
*Speed Pro cam: Intake 224 deg duration, .450" Lift - Exhaust 224 deg duration, .460" lift
*New hydr lifters and push rods
*Sportsman II heads with 72cc chambers, 9.5 :1 compression, stainless valves 2.02 intake, 1.6 exhaust, heavy duty valve springs, screw in studs, guide plates
*Crane roller rocker arms (rollers on both fulcrum and tip)
*Edelbrock Performer RPM aluminum intake manifold
*Edelbrock #1470 750cfm 4 barrel carb
*HEI distrib
*Dyna-Max Headers

Here is my question... He said to run 20W-50 racing oil in it, so I'm using 20W-50 Casterol. Oil pressure on start up initally is above 80 psi. After driving it awhile it drops to say 60 psi when driving and 80 psi under moderately heavy acceleration. It is oh, say 40-60 at idle when warm.

The 80 and above seems high to me. Also, the 20W-50 seems like it will be too thick once summer is gone.

Is the pressure just a result of the high volume, high pressure oil pump, or the "heavy" oil? Would it be a bad thing to go to 10W-40 oil?

I'm new to high performance engines and don't want to screw up and make an expensive mistake by doing something stupid, or by not doing something I should.

As usual, thanks for any help and insights.

junkyardjohn · 08-25-2003, 11:38 PM

I LIVE IN NEVADA, WHERE IT GETS PRETTY WARM. I'VE BUILT AN AWFUL LOT OF HI PERF. ENGINES (BOTH BB & SB) & I RUN 20W50 IN THE SUMMER MONTHS, BUT THINK NOTHING BAD ABOUT RUNNING 10W30 OR 10W40 IN THE WINTER. YOU'LL EXPERIANCE LOWER OIL PRESSURE WITH THE THINNER OIL ONCE YOUR ENGINE GETS WARM, BUT NOT TO WORRY. THE RULE OF THUMB IS 10 LBS OF OIL PRESSURE FOR EVERY 1000 RPMS YOUR ENGINE IS RUNNING. LOTS OF CLEAN FRESH OIL IS THE KEY TO ENGINE LONGEVITY. CHANGE IT OFTEN. JOHN

Lobo'74 · 08-26-2003, 08:01 AM

Thanks for the information. The "rule of thumb" is good to know.

08-25-2003, 11:38 PM	#2
junkyardjohn Registered User Join Date: Aug 2001 Location: SOMERSET KY. Posts: 6,427	I LIVE IN NEVADA, WHERE IT GETS PRETTY WARM. I'VE BUILT AN AWFUL LOT OF HI PERF. ENGINES (BOTH BB & SB) & I RUN 20W50 IN THE SUMMER MONTHS, BUT THINK NOTHING BAD ABOUT RUNNING 10W30 OR 10W40 IN THE WINTER. YOU'LL EXPERIANCE LOWER OIL PRESSURE WITH THE THINNER OIL ONCE YOUR ENGINE GETS WARM, BUT NOT TO WORRY. THE RULE OF THUMB IS 10 LBS OF OIL PRESSURE FOR EVERY 1000 RPMS YOUR ENGINE IS RUNNING. LOTS OF CLEAN FRESH OIL IS THE KEY TO ENGINE LONGEVITY. CHANGE IT OFTEN. JOHN __________________ junkyardjohn 69 1 TON TOW TRUCK // 84 4WD CUCV BLAZER// 85 1 TON 4WD STAKE TRUCK// 86 M1031 5/4 TON 4WD CUCV// ALOT OF OLD TRUCKS FOR ONE OLD MAN TO DRIVE. THERES ROOM FOR ALL OF GODS CREATURES RIGHT NEXT TO MY MASHED POTATOES// LIFE MEMBER OF P.E.T.A (PEOPLE EATING TASTY ANIMALS) DON'T RENT U-HAUL ALWAYS TELL THE TRUTH IT WILL AMAZE PART OF THE PEOPLE & ASTONISH THE REST Last edited by junkyardjohn; 08-25-2003 at 11:41 PM.

08-26-2003, 08:01 AM	#3
Lobo'74 Registered User Join Date: Nov 2002 Location: Charlottesville, VA Posts: 404	Thanks Thanks for the information. The "rule of thumb" is good to know. __________________ "Truck" '67 small window '79 350 .030 over, LT1 "clone"

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08-25-2003, 11:24 PM	#1
Lobo'74 Registered User Join Date: Nov 2002 Location: Charlottesville, VA Posts: 404	Oil Pressure Question The engine in my '67 is a '79 350 that was rebuilt by the previous owner to the following specs: 350, 4 bolt mains Bored .030 over Align Bored Parallel top of block New Cam bearings New freeze plugs New hypereutecic pistons, flat top Reconditioned connecting rods Crankshaft main and rod journals ground .010 under rotating assembly balanced Double roller timing chain Melling high volume, high pressure oil pump Speed Pro cam: Intake 224 deg duration, .450" Lift - Exhaust 224 deg duration, .460" lift New hydr lifters and push rods Sportsman II heads with 72cc chambers, 9.5 :1 compression, stainless valves 2.02 intake, 1.6 exhaust, heavy duty valve springs, screw in studs, guide plates Crane roller rocker arms (rollers on both fulcrum and tip) Edelbrock Performer RPM aluminum intake manifold Edelbrock #1470 750cfm 4 barrel carb HEI distrib Dyna-Max Headers Here is my question... He said to run 20W-50 racing oil in it, so I'm using 20W-50 Casterol. Oil pressure on start up initally is above 80 psi. After driving it awhile it drops to say 60 psi when driving and 80 psi under moderately heavy acceleration. It is oh, say 40-60 at idle when warm. The 80 and above seems high to me. Also, the 20W-50 seems like it will be too thick once summer is gone. Is the pressure just a result of the high volume, high pressure oil pump, or the "heavy" oil? Would it be a bad thing to go to 10W-40 oil? I'm new to high performance engines and don't want to screw up and make an expensive mistake by doing something stupid, or by not doing something I should. As usual, thanks for any help and insights. __________________ "Truck" '67 small window '79 350 .030 over, LT1 "clone"



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