Proper oil pressure for C3
Le Mans Master
Joined: Oct 2006
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From: Palmdale CA
Depends on the oil pump. Could go as low as 20 at idle and between 60 to 80 at RPM. That's for a Melling High Pressure, High Volume Oil pump. It will always drop at idle, because it's driven off the camshaft.
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It also depends on the viscosity of the oil and the accuracy of the guage. When my other SBC motors are hot and idling with 10w30 I have seen almost no readable pressure on some guages but it would jump up as soon as the pedal was touched.
A good rule of thumb is 1 lb for every 100 rpm. so 7 lbs at idle and 50 at 5000 rpm but your pump may top out at 30 to 40 psi. If you are not running high RPM for a time like 1/4 mile or slalom racing or someting similar, then 35 to 40 would be fine.
I run a mellings High volume/ high pressure pump but have 7 usable quarts in a Milodon pan. The higher the volume the pump, the more oil you may have up in your valve covers and not in the pan. I also use Mobil1 20w50 for the phospor and zinc. My pressure is 30 to 35 at idle when hot and 70 when cruising, but again it is due to the pump and viscosity i run.
A good rule of thumb is 1 lb for every 100 rpm. so 7 lbs at idle and 50 at 5000 rpm but your pump may top out at 30 to 40 psi. If you are not running high RPM for a time like 1/4 mile or slalom racing or someting similar, then 35 to 40 would be fine.
I run a mellings High volume/ high pressure pump but have 7 usable quarts in a Milodon pan. The higher the volume the pump, the more oil you may have up in your valve covers and not in the pan. I also use Mobil1 20w50 for the phospor and zinc. My pressure is 30 to 35 at idle when hot and 70 when cruising, but again it is due to the pump and viscosity i run.
Last edited by Rescue Rogers; Jun 16, 2019 at 11:40 AM.
Thread Starter
8th Gear
Joined: Dec 2017
Posts: 8
Likes: 0
From: Weatogue Ct.
oil pressure
Thanks for impute guys. After taking my oil pump apart I found the slide piston stuck open the spring is suppose to control. I freed it up and put in a new purple spring. Mine is a Melling M55-HV pump as well.
Team Owner
Joined: Apr 1999
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From: Reno Nevada
2024 C3 of the Year Finalist- Modified
When using HV pumps you need to put some thought into larger volume pan, limiting oil restrictors to the top end, and block off the oil filter bypass
Le Mans Master
Joined: Aug 2017
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From: Cool Northern Michigan
Not trying to steal your thread Richard, but I have the Melling 55HV with the purple spring as well plus extra Qt pan, and would like to hear more about the filter by-pass.
Previous posts said you should never do this. Others say its ok.
What could go wrong? Right?
Also, a excellent video on YouTube by a pretty sharp hot rodder says its impossible for a Melling High Volume pump to empty a oil pan. He said its an old myth. Just not going to happen. The pickup tube is not capable of moving that many quarts per minute.
I will say that with some aluminum heads, the drain-back holes at each end of the head are, well, a little disappointing. Mine has a puddle there every time I pull the valve cover. Looks like a lot of oil standing, but likely is only a tablespoon.
Previous posts said you should never do this. Others say its ok.
What could go wrong? Right?
Also, a excellent video on YouTube by a pretty sharp hot rodder says its impossible for a Melling High Volume pump to empty a oil pan. He said its an old myth. Just not going to happen. The pickup tube is not capable of moving that many quarts per minute.
I will say that with some aluminum heads, the drain-back holes at each end of the head are, well, a little disappointing. Mine has a puddle there every time I pull the valve cover. Looks like a lot of oil standing, but likely is only a tablespoon.
Last edited by HeadsU.P.; Jun 28, 2019 at 11:34 AM.
Drifting
Joined: Jun 2012
Posts: 1,990
Likes: 183
From: Port St. Lucie Fl
Not trying to steal your thread Richard, but I have the Melling 55HV with the purple spring as well plus extra Qt pan, and would like to hear more about the filter by-pass.
Previous posts said you should never do this. Others say its ok.
What could go wrong? Right?
Also, a excellent video on YouTube by a pretty sharp hot rodder says its impossible for a Melling High Volume pump to empty a oil pan. He said its an old myth. Just not going to happen. The pickup tube is not capable of moving that many quarts per minute.
I will say that with some aluminum heads, the drain-back holes at each end of the head are, well, a little disappointing. Mine has a puddle there every time I pull the valve cover. Looks like a lot of oil standing, but likely is only a tablespoon.
Previous posts said you should never do this. Others say its ok.
What could go wrong? Right?
Also, a excellent video on YouTube by a pretty sharp hot rodder says its impossible for a Melling High Volume pump to empty a oil pan. He said its an old myth. Just not going to happen. The pickup tube is not capable of moving that many quarts per minute.
I will say that with some aluminum heads, the drain-back holes at each end of the head are, well, a little disappointing. Mine has a puddle there every time I pull the valve cover. Looks like a lot of oil standing, but likely is only a tablespoon.
Team Owner
Joined: Apr 1999
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From: Reno Nevada
2024 C3 of the Year Finalist- Modified
It is not just the total flow of the pump tube that can be the problem. what if you are hauling a$$ on a long freeway on or off ramp and the "G" forces move what little oil is left in the pan over away from the pickup? I used to get a flickering oil pump light going around turns with a 8 quart road racing pan.
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From: altered state
St. Jude Donor '05
no need to on most st engines, as said a high rpm I always plug it; a std volume Z28 spring is good enough also
Just use a good quality oil filter and let the oil get good and hot before leaning on it.
Youll know when your idle oil pressure drops significantly from cold.
Just use a good quality oil filter and let the oil get good and hot before leaning on it.
Youll know when your idle oil pressure drops significantly from cold.