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06-18-2004, 11:00 PM | #1 |
Keep it gangsta!
Join Date: Dec 2003
Location: Peoria, Arizona (Phoenix Area)
Posts: 102
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Oil pressure...how low is too low?
I have a '78 C20 with a rebuilt 350 and 700R4, I use Valvoline 10w30. At highway speeds it produces around 30 psi of pressure, and when it's at idle it produces around 5 psi. I have used 20w50 and it raised just a little bit, but not that much, I have installed an aftermarket mechanical guage to verify this.
Is this pressure acceptable? If not, what is the problem?
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1984 K5 Blazer 305-NP208-700R4 Ex Police Unit It's old school, but moves along nicely... '78 C-20 - SOLD |
06-18-2004, 11:24 PM | #2 |
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Location: Ferndale, Michigan, USA
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You should have 10 - 12 psi at idle with no less than 7 psi. Some of the things that can cause low oil pressure are a poor fit of the distributor, too large bearing clearence, oil pump of low quality reman, stuck pressure relief valve and loose or missing galley plugs. Good luck with it.
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06-18-2004, 11:52 PM | #3 |
california fill
Join Date: Apr 2004
Location: Sunny So-Cal
Posts: 694
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I wouldnt worry about it.. 5psi is a little low, but as long as its keeping the oil moving, you'll be fine. Its the pressure @ highway speeds thats really important.
pc |
06-19-2004, 02:18 AM | #4 |
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Join Date: May 2004
Location: L.A. Style Capital of the World
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Your pressure is too low, you need to find the cause. How many miles does the motor have on it? did you consider using a stronger check valve spring ? at very least pull you oil pump and do a thorough inspection.
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06-19-2004, 04:19 PM | #5 |
Truck CRAZY!
Join Date: Mar 2004
Location: douglas
Posts: 81
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I disagree with every1 i think that 5 psi at idle is enough as long as the oil is moving because I have seen chevroelt motors run on that kind of oil pressure for a long time and if it dosent go below 5psi you should be find but below 5 I would try to fix i then
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06-19-2004, 07:22 PM | #6 |
Senior Member
Join Date: Jul 2003
Location: Indianapolis, IN
Posts: 1,277
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Too low is when the hydraulic lifters won't stay pumped up at idle, you can use the oil pressure gauge for a tach, and it take straight 50w oil to keep any oil pressure at speed. Aks me how I know.
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06-22-2004, 11:28 PM | #7 |
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Location: Ferndale, Michigan, USA
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What's wrong with you people? If you have 5 psi of oil at the REAR of the engine do you really think that you have enough pressure and flow at the FRONT. Can you say wipped out #1 main bearing.
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06-22-2004, 11:41 PM | #8 |
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Location: Lubbock, Texas
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man dont get me started on that, we have a satanic 454 out in the shop that doesn't like to hold oil presure. so far its killed, 2 cams, 1 crank and 1 set of crank and rod bearings. some blocks are made from the factory to hold and have high oil presure and some arnt its jsut the luck of the draw.
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06-23-2004, 01:10 AM | #9 |
Keep it gangsta!
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I think I have solved the prob. I went and bought a tach, turns out that my idle speed was like 400 rpm, cranked that up a little to 800 like the cam manufacturer recommends and everything is cool, now up to 15 lbs at hot idle in drive, jumps up past 20 in park.
Thnaks for all the info, I was kind of worried there
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1984 K5 Blazer 305-NP208-700R4 Ex Police Unit It's old school, but moves along nicely... '78 C-20 - SOLD |
06-23-2004, 01:25 AM | #10 |
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Location: Rosemount, MN
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10# per 1,000 rpm, 15 -20# at idle. If less than that you have an unwanted,( usually to much clearance somewhere, or possibly porosity.), internal leak. You will be surprised at what an old big block or small block will run on. Want to scare yourself, put a -4 AN line on the front main plug, plumb it to a high quality oil pressure guage, go 30mph, then hit the brakes hard. You wouldn't believe how much that guage dances around if your short a little oil What I said about oil pressre is with the proper clearances in the bottom end. There are approx. 100 leaks in the bottom end of a chevrolet engine, rods, mains,lifters ect. These are by design. Look in an overhaul manual for proper clearances. If the engine runs good and doesn't rattle the lifters, drive it sometimes the stock guage or sender is screwed up.
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06-23-2004, 01:32 AM | #11 |
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Location: Rosemount, MN
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Another answer; run it till it blows up, then put a little more oil pressure in the next one
(that's a joke, I hope you people took it as one). I've built numerous BBC & SBC street and drag race engines. |
06-23-2004, 10:08 AM | #12 |
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Location: Lewisville, NC
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Unless one is going to throw a rod I run um till their dead. If its going to get rebuilt by me i'm not paying to machine all the old stuff, it will get a new rotating assembly anyway. I get about 10 on my 350 at idle with 10w-30, about 40 psi running down the highway.
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1985 Scottsdale Shortbed 4x4 Stout 350 with some "upgrades"-700r4-33x12.5" Mud Tires, Warn 8274-50 winch. 2005 Chevrolet Colorado Regular Cab 2wd 4-banger, 5 speed, Street Pack with 3.73 axle. |
06-24-2004, 09:01 AM | #13 |
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Location: Atlanta GA
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I ran one fore a year that made 3psi hot idle. Never rattled a lifter. Was running fine. It was thrust bearings on that motor. I think the PO installed the harmonic with a hammer and that was the cause.
Main bearings are cheap. If it's a other wise good running engine with good compression then tossing some bearings it it will buy you a couple more years out of it.
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06-24-2004, 10:19 PM | #14 |
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maybe i'm use to the old deisels at work, but i don't wanna have oil press lower than 10 psi idle hot. thats just me. any lower than that, i feel i have a prob somewhere and will investigate why my oil press is that low. but agian, that is me.
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79 Chevy Silverado 454, TH350 4.11:1 posi. 03 Subaru WRX Wagon, EJ20 5MT AWD. 53 Chevy 3100. 216, 3MT, 4.11:1 |
06-24-2004, 11:38 PM | #15 |
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Location: Milwaukee, Wisconsin
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man...now ya'll got me worried....my '78 350/sm465 idles with a psi of 0 at 350/400rpms....about about 30 at 2000rpms (main cruising rpm)....doesn't rattle at all tho....not that i've noticed.
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Paul D. '78 C20 Scottsdale 350ci 3 speed with granny gear 14 bolt rearend My trucks are "Car-Guy safe".......which pretty much means death trap in the hands of a normal civilian. |
06-24-2004, 11:39 PM | #16 |
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0 psi is never good
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'96 Nissan Pathfinder '02 Firebird Trans Am. '88 K5 Blazer |
06-24-2004, 11:45 PM | #17 |
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i just figure the gauge is fubar....mine on my last truck was and it was newer then this one....the engine sounds healthy...no rattles or knocks or anything. gonna check this weekend with a mechanical gauge tho just to be sure.
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Paul D. '78 C20 Scottsdale 350ci 3 speed with granny gear 14 bolt rearend My trucks are "Car-Guy safe".......which pretty much means death trap in the hands of a normal civilian. |
06-25-2004, 12:47 AM | #18 |
california fill
Join Date: Apr 2004
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I do agree with sanitysbane, in that zero psi is never good
if you have an old electronic guage, I wouldnt assume its all that accurate. Pull the valve cover(s) and make sure the rockers are getting oil at idle. If they are, drive it like you stole it. If not, then radio houston, because, we have a problem. pc |
06-25-2004, 08:01 AM | #19 | |
Tonawanda 454
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Quote:
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91 Chevy Suburban Tonawanda 454 R2500 - SOLD!!! 04 Dodge Durango 5.7L Hemi 2WD, 24K miles (as of July 2011) In the past 30 years about 90% of Fords are still on the road, the other 10% made it home. ------------------- |
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07-11-2004, 02:10 AM | #20 | |
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Quote:
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