Oil Pressure
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TECH Enthusiast
Joined: Jun 2005
Posts: 546
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From: Wichita, KS
Oil Pressure I just got done doing my top end build a few months ago where I replaced my factory oil pump with a Melling 10295 pump. Since then, I have been trying to chase down a low oil pressure issue.
I have 21psi hot idle, ~40psi+ cruise, and 50+ WOT. From what I can tell most people have around 40psi hot and 65+ WOT-- This is why I think I have low oil pressure.
I have checked my pickup tube o-ring and it looks perfect. It had 400 miles on it, and looked brand new, but I still replaced it with a new GM one when I put it back together. While it was apart I replaced the cam gasket / retainer plate.
I have tried 5w-30 and 0w-40 Mobil 1, as well as mobil 1 filter and K&N Filter. NONE of this made a difference. Oil pressure remains the same.
Tonight I installed an aftermarket gauge. I installed the sending unit above the oil filter, and it pretty much mirrors the factory gauge.
So now I'm wondering what my next steps should be.. Run the car until it blows up? Replace the oil pump with a ported LS6 unit? Park the car and buy a 383 short block? Go in the corner and cry?
I have 21psi hot idle, ~40psi+ cruise, and 50+ WOT. From what I can tell most people have around 40psi hot and 65+ WOT-- This is why I think I have low oil pressure.
I have checked my pickup tube o-ring and it looks perfect. It had 400 miles on it, and looked brand new, but I still replaced it with a new GM one when I put it back together. While it was apart I replaced the cam gasket / retainer plate.
I have tried 5w-30 and 0w-40 Mobil 1, as well as mobil 1 filter and K&N Filter. NONE of this made a difference. Oil pressure remains the same.
Tonight I installed an aftermarket gauge. I installed the sending unit above the oil filter, and it pretty much mirrors the factory gauge.
So now I'm wondering what my next steps should be.. Run the car until it blows up? Replace the oil pump with a ported LS6 unit? Park the car and buy a 383 short block? Go in the corner and cry?
I believe you did everything you could do man, just run it till it goes. I think your clearances just opened up. Might try 10w30 a lil thicker oil . Once it starts gettin into like 12-15 psi I'd get worried . 21is ok for idle but it shoots way up when you step on it and that's a good sign
How was the pressure on the old pump?
Not that it will make you fell better but GM service manual says at operating temperature minimum pressures.
6 psi @ 1000 rpm
18psi @ 2000 rpm
24psi @ 4000 rpm
Not that it will make you fell better but GM service manual says at operating temperature minimum pressures.
6 psi @ 1000 rpm
18psi @ 2000 rpm
24psi @ 4000 rpm
Thread Starter
TECH Enthusiast
Joined: Jun 2005
Posts: 546
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From: Wichita, KS
I'm not sure how the old pump was... I never really paid attention, as I've only had the car a few years, and don't drive it that often. I have 1 picture of it at 35psi at hot idle, but I'm not sure how hot the oil was.
As soon as I give it gas, the oil shoots up to 40+psi. I'm fine with driving it until the bottom end goes, but I don't want it to take out my new Mamo heads in the process!
As soon as I give it gas, the oil shoots up to 40+psi. I'm fine with driving it until the bottom end goes, but I don't want it to take out my new Mamo heads in the process!
Well I wouldn't worry that it's on the verge of blowing up I seriously doubt it's that much of an issue, That oil pressure isn't that bad at all. I'd run it as normal and watch it as you normally would. Most engines that blow up due to lack of pressure usually spin bearings not throw rods or drop valves. The only reason a spun bearing would kill heads would be a rod bearing failing allowing the piston to travel a little further up the bore and kissing a valve and even then it doesn't happen often that I've seen.
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Thread Starter
TECH Enthusiast
Joined: Jun 2005
Posts: 546
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From: Wichita, KS
Yeah, I'm not exactly sure how much pressure I'm getting at WOT @ 6800rpm, it's hard to look at the gauge and the road. I know it's close to 60, but I'm not 100% sure. When I rev in park it hits 60+.
I also have air bubbles on the dipstick, but I had them before I verified and replaced the o-ring as well. I've heard from many that the air bubble on dipstick isn't a great way to verify an o-ring issue. The rotating assembly can aerate the oil and cause bubbles.
Sorry if I sound paranoid guys, but the truth is I am paranoid!
I also have air bubbles on the dipstick, but I had them before I verified and replaced the o-ring as well. I've heard from many that the air bubble on dipstick isn't a great way to verify an o-ring issue. The rotating assembly can aerate the oil and cause bubbles.
Sorry if I sound paranoid guys, but the truth is I am paranoid!
12 Second Club
Joined: Sep 2005
Posts: 4,273
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From: Bucks County, Pa.
You're definitely NOT overfilling the oil level by too much (not more than 1 quart over), correct??
I'm wondering if the Improved Racing crank scraper could help your aeration issue?
I'm wondering if the Improved Racing crank scraper could help your aeration issue?
TECH Regular
Joined: Dec 2011
Posts: 448
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From: SoCal
If you want to pick the pressure up a bit move to 10W40. It will cost a few hp but nothing the but dyno will show. Remember pressure is nothing more than resistance to flow. Increased bearing clearances will cause lower pressures as will porting/smoothing oil paths. You just did a top end so what you are seeing is a broken in bottom end with increased clearances. If you start seeing fluctuations in pressure under same load/rpm then I would be worried. One last thing is use. If you are road tracking this car where oil temps are going through the roof then definitely run a higher viscosity synthetic.
Thread Starter
TECH Enthusiast
Joined: Jun 2005
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From: Wichita, KS
Thanks, Travis. Tony's advice was to run 10w-40, as well. I got to thinking, wouldn't 10w-40 just increase my cold start pressure, since I'm already running 0w-40?
And no road racing, this is 100% street car. I just don't want to be afraid to beat the hell out of it.
And no road racing, this is 100% street car. I just don't want to be afraid to beat the hell out of it.
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Joined: Dec 2011
Posts: 448
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From: SoCal
I'm running 10w40 and I see cold pressure of 85psi idle and it settles in at 48-50 idle. Yours will be less but I'd bet you will see a pressure increase. Also that is using conventional oil so synthetic will be less of a swing.