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Discussion Starter · #1 ·
First I know there’s lots of posts on this but I can’t find out why.
stats. 350, 60 over new everything. Forged crank, pistons , H rods, afr heads( 210cc flow)
total seal rings. New oil pump, it’s a shark tooth style hi pressure and volume. The motor is meant for just drag racing.
mains are at 0.0010
Rods are at 0.0010.
oil galley in front has been taped and Allen caps installed. The plug at the bottom of the oil pressure line is there. Running a dual remote filter system (earls)
Prime the motor and it has 35 psi
Start and run for 5 minutes and is at 20 psi , does go up when on the gas.
So my question is where is the pressure going?
no lifter noise ( does have a solid lifters)
No knocking.
gauges are new also I run a dummy light.
 

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More for Less Racer
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21,220 Posts
Agree with Johnsongrass1, filter change is first troubleshooting step.

Was the bypass in the pump removed and checked for trash in the bore and checked for free movement with no sticking??
Bypass might be stuck partially open...
What's the pressure at 5000 rpm?

Any new pump should be dissassembled and checked over before use.
 

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1949 Ford Coupe RESURRECTION
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1,148 Posts
20 psi at idle? When it goes up, how far is up? What is it at 1500 rpm? 2500 rpm? Is the gauge accurate? New doesn't necessarily mean accurate. Check its calibration before getting worried..

Let us know what you find
 

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Weight of oil, temperature of the engine, RPMs at the indicated pressure is necessary information.

Pressure varies by RPM so where it goes at what RPMs is important information.

Rod and main clearances are awfully tight, at .001 what gives here, are you sure about these?

Gauges being new doesn’t assure accuracy. Are they mechanical or electric? Same gauge used for priming the oil system as used when firing the engine?

Bogie
 

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First I agree that rod and main clearances are too tight for a racing engine. Usually racing engines are built with looser tolerances and that is tight even for a street engine.

What oil pressure does the engine have when cranking?

Could the high volume pump be sucking the pan "almost" dry and most of your oil be up in the top of the engine? Does it repeat the scenario of higher pressure upon start up and then dropping later, or did it do that the first time and then just stay at the low pressure from then on?

What keeps your bearings cool is flow. Even if you put a high volume pump on it, it cannot flow more oil thru the bearings if the clearance is too tight. All of your clearances are basically "orifices" that let oil flow. Smaller clearance = smaller orifice=less flow.............so your pumps excess flow is bypassed and you gain nothing. The flow may however go thru the other clearance/orifices that have less resistance. Here is one of my favorite videos.

and another one

 

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Member - AMC/Rambler "guru"
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20 psi at hot idle (engine fully warmed up) isn't really low. The real issue here is how much does it go up at rpm? The old rule of thumb is 10 psi per 1000 rpm, which would be 30 psi @ 1000 rpm (idle at 600 or so), 40 @ 2000, etc. Modern engines usually have more than that though. At 3000 rpm it should have about 60 psi, though 50 would be considered adequate.
 

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'23 T-Bucket Pickup
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1,863 Posts
20 psi at hot idle (engine fully warmed up) isn't really low. The real issue here is how much does it go up at rpm? The old rule of thumb is 10 psi per 1000 rpm, which would be 30 psi @ 1000 rpm (idle at 600 or so), 40 @ 2000, etc. Modern engines usually have more than that though. At 3000 rpm it should have about 60 psi, though 50 would be considered adequate.
Not so sure about oil pressure being 60 psi. Along with myself there were a bunch of us foremen with brand new Chevy pickups in 2009 that never had more than 35 psi oil pressure at speed. Older stock vehicles were limited to 40 psi. I put a 60 psi spring in a 231 Buick V-6 when I rebuilt it for a customer. It blew apart the oil filter if I gave it any throttle at all at cold winter start. I put in the 40 psi spring before I released the car to the customer.
 

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Member - AMC/Rambler "guru"
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1,851 Posts
Not so sure about oil pressure being 60 psi. Along with myself there were a bunch of us foremen with brand new Chevy pickups in 2009 that never had more than 35 psi oil pressure at speed. Older stock vehicles were limited to 40 psi. I put a 60 psi spring in a 231 Buick V-6 when I rebuilt it for a customer. It blew apart the oil filter if I gave it any throttle at all at cold winter start. I put in the 40 psi spring before I released the car to the customer.

Well, I'm an AMC guy, and they hold 60+ psi. Haven't messed with a Chevy or Ford in 25-30 years. Forget the specs on them!
 

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'23 T-Bucket Pickup
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Well, I'm an AMC guy, and they hold 60+ psi. Haven't messed with a Chevy or Ford in 25-30 years. Forget the specs on them!
FWIW. Ford pressure switches for the low oil pressure light closed @ 7 psi. In 1984 and 1985 I had d to roll in main and rod bearings on several 351M and 400M engines built in the late 70s and early 80s, that developed low oil pressure problems at around 75000 miles. I used a mechanical oil pressure gauge to verify the oil pressure. Had to put as much as a .003 shim under the bearing caps, along with new bearings, to get proper oil clearance. Apparently had soft cranks as well as poor bearings. Same problem with the Ford 300 I6.
 
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FWIW. Ford pressure switches for the low oil pressure light closed @ 7 psi. In 1984 and 1985 I had d to roll in main and rod bearings on several 351M and 400M engines built in the late 70s and early 80s, that developed low oil pressure problems at around 75000 miles. I used a mechanical oil pressure gauge to verify the oil pressure. Had to put as much as a .003 shim under the bearing caps, along with new bearings, to get proper oil clearance. Apparently had soft cranks as well as poor bearings. Same problem with the Ford 300 I6.
I have a 468 cu in Olds in my "81 Firebird for Bracket Racing and my warm oil pressure i 35 - 40 at idle (750 RPM) and 60 - 70psi at 3000 RPM.
At start up it's 80 [email protected] 1,000 RPM ..... I have 3,000 - 5,000 miles on it as it's my "daily drive" also. - Jerry
 

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'23 T-Bucket Pickup
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1,863 Posts
I have a 468 cu in Olds in my "81 Firebird for Bracket Racing and my warm oil pressure i 35 - 40 at idle (750 RPM) and 60 - 70psi at 3000 RPM.
At start up it's 80 [email protected] 1,000 RPM ..... I have 3,000 - 5,000 miles on it as it's my "daily drive" also. - Jerry
When I rebuilt the 5.7 vortec in in 98 Silverado I put the rod and main oil clearances @ .0015 and installed a high volume supposedly standard pressure pump. It also has over 80 psi at cold idle and runs 60 psi hot on the highway. Previous oil psi was limited to 40 lbs with stock pump. About 20 psi at hot idle.
 

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Member - AMC/Rambler "guru"
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Vortecs and LS engines have more oil pressure than the old 50-80s SBCs. They might have similarities, but totally different animals! A lot of the old hot rod "rules of thumb" are based on the older engines and no longer apply to newer models.
 

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True Hotrodder
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1,955 Posts
When I rebuilt the 5.7 vortec in in 98 Silverado I put the rod and main oil clearances @ .0015 and installed a high volume supposedly standard pressure pump. It also has over 80 psi at cold idle and runs 60 psi hot on the highway. Previous oil psi was limited to 40 lbs with stock pump. About 20 psi at hot idle.
So that's .00075 between the bearing and journal - if that oil pump coughs one time on a suck of air.
 
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