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Discussion Starter #1
I've got a good one for you guys.

The mystery motor in my 71 runs great but i'm told its at least 6 seasons old. It's a smallblock that I got for free and the previous owner told me its a circle track 393 cube engine with 200cc Dart Iron Eagles and is supposed to have 12.0-1 compession. I run a mixture of Valvoline VR-1 and Lucas oil stabilizer.

When I start the car the Autometer ultralite mechanical oil pressure gauge reads 60psi and when it reaches operating temp it goes to about 20-30. When I'm out cruising around and stopped at a stop light it will drop to 10psi or 5psi or 0psi!!!

There is no rod knock just a noisy valvetrain. I was thinking that the rod and main clearances are too loose and the oil pump might be an anti cavitation style which is supposed to have low pressure at lower rpm's. I have driven the car like this for two summers! haha. I'm in the process of finishing my 421 so I really am not too concerned about the oil pressure, just wanted to see what you all think.

Any ideas fellas??
 

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Maybe your engine is really dirty, or you got a lot of sludge on the top end blocking passages down to the sump, and not draining to your oil pan thus giving you a reading of 0.

Or you have a bad gauge.
 

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Please school this guy on why it could be the cam bearings. And why would the oil pressure act that way with bad cam beaarings?:confused:
-Pat
 

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Please school this guy on why it could be the cam bearings. And why would the oil pressure act that way with bad cam beaarings?:confused:
-Pat
Cam bearings cam to mind 1st but it could also be a weak oil pump or worn main and rod bearings. No way of pin pointing the issue without actually inspectioning the bearings
 

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My old 355 did that for four years. I replaced rod and mains 3 times and cam bearings once. It's still going strong today in a friends car. I replaced the cam and lifters as well along with the gauge twice. I still never fixed the problem.
 

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Back in 72 at GM training in Omaha the TI told us he would run a sbc across country with 5 pounds of oil pressure and not worry about. He said it wasn't optimum but he'd do it.....but that was a stock 350 also.
 

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If you have a good pump and low pressure the motor may not blow up but it is hemorraging oil internally which is why you have low pressure. All that oil is flying around inside the motor and using power to beat it away from the rotating assembly. You can have excessive side clearances on rods and the motor may run fine but it will use some power because of the oil hemorraging out of the rods. A well built, properly clearanced, race engine, in good shape won't loss a bunch of oil pressure from idle to max RPMs and back down and it won't have a ton of oil pressure when it's hot.
 

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Bearings(cam, rods or mains), rod side clearance, too much lifter clearance or too much clearance in the oil pump can cause these issues.

Crew brought in one of our crewtrucks with no oil pressure. They towed it in and it wasn't knocking, but the lifters were ticking. Installed a new pump and no problems. Drove it for a bunch more years then they sold it as we got a new crew truck for them.
 

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circle track

do you think the motor built for circle track maybe had that in mind since its only run full tilt? Maybe not, lol. Either way it was free and still rocking. sweet!
 

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Discussion Starter #14
If you have a good pump and low pressure the motor may not blow up but it is hemorraging oil internally which is why you have low pressure. All that oil is flying around inside the motor and using power to beat it away from the rotating assembly. You can have excessive side clearances on rods and the motor may run fine but it will use some power because of the oil hemorraging out of the rods. A well built, properly clearanced, race engine, in good shape won't loss a bunch of oil pressure from idle to max RPMs and back down and it won't have a ton of oil pressure when it's hot.
I agree, I believe the rod and main clearances are out of whack.
 

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Discussion Starter #15
do you think the motor built for circle track maybe had that in mind since its only run full tilt? Maybe not, lol. Either way it was free and still rocking. sweet!
Yup! can't beat free! But that's what I think, circle track motor with an anti cavatation pump. There is a Moroso unit that is labeled "anti cavatation" for circle track use.
 

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very interesting comments my motor does almost the same thing, ive got 60 [email protected] 3-6 grand and at idle its 15psi but im running a moroso windaqe tray, do you think thats the reason for the low psi at idle i dont have any rattles or nocks,but it is a high volume oil pump and stock pan
 
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