I just changed the oil a week ago and used 10w40. I had 50W in there earlier and noticed I was about 1 1/2 qts low (give or take with what was in the filters).

As it did before, it will read about 45psi at idle when I first start up the engine in the morning., but as it warms up, the oil psi will read around 10 psi at idle! The psi goes up as the rpms do, so I'm not too woried. But is it normal for oil psi to drop so much as it warms up?

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1984 z28 w/ a 357 cu in. monster engine which is looking like the posterchild for Edelbrock with the exception of the Holley 750vac... all the suspension stuff... 9-bolt posi disk is in...

-=ICON Motorsports=-

 

Yes that is normal, once the oil heats up it isn't as thick causing a loss in pressure. A rule of thumb is for every 1k rpm you should divide that by 100. EX: 2500rpm 25psi.

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"Rice burners are like tampons...Every pu$$y has to have one"
'86 IROC
T-TOPS, TINTED WINDOWS, BRAKE LIGHT BLACKOUTS
GM GOODWRENCH 350
EDELBROCK TES HEADERS
3" Hooker CatBack w/Aero Chamber muffler
EDELBROCK 600CFM CARB.
KN AIRFILTER
ACCEL HEI DISTRIBUTOR
160* Stat
3:73 Posi
Rebuilt 700R4
B&M Megashifter, 5" Autometer Tach w/shift lite

 

I'd say you're fine, although mine runs a higher pressure even with 10W-30 or 5W-30 synthetic.

Can I ask why you were running a straight 50W oil in it? That's just a bit on the thick side to provide good start-up lubrication. I wouldn't do that, unless it's Mobil 1 15W-50.

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1990 IROC 350
Mods: Too busy trying to make it run right to mod it.
Airfoil, Dynomax cat-back, MSD coil, 180 t-stat, Bald Eagle tires,
Hypertech fan switch, Accel 23# injectors, Holley module, ported plenum,
Ported Daytona Yellow stock base, Moroso valve covers, other stuff,
Streetdampr, Ruger P95DC, hot wife, new oil filter, !cats, !TBC, !AIR.
18.0 @ 85MPH since I'm one big-a$$ MF
"It's better to have and not need than to need and not have."

 

It was Valvoline 50W racing oil... thought I'd try it being that my psi traditionally was so low. I liked it and it worked well for 3000 miles... maybe more.

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1984 z28 w/ a 357 cu in. monster engine which is looking like the posterchild for Edelbrock with the exception of the Holley 750vac... all the suspension stuff... 9-bolt posi disk is in...

-=ICON Motorsports=-

 

Stock oil pressure senders and guages are often WAY off. The oil pressure gague in my 91 was like a random number generator. Changed the sending unit and that helped some, but sometimes the pressure would read ZERO at idle. Mechanical gague told me the truth: 25 at idle hot, 55 revved up. I ignored the stock electrical gague after that.

 

Not to scare you or anything, I do beleive your pressure guage may be at fault. But, about a year ago my truck was having a very similar problem "mechanical guage" and it was a crappy oil pump that went bad. It still pumped oil but not engough, eventually the lack of lubrication destroyed my crank. My pressure was around 45 cold 10/15 hot. So If I were you I would hook up a mechanical guage to make sure or consider a new oil pump.
SSC


Edit: That 10/15 PSI was at Idle, it did go up to about 30ish PSI driving down the road.


[This message has been edited by SSC (edited October 05, 2001).]

 

my 88 iroc was doing the samething but at idle my gauge would read irraticaly 5-30psi.also i was losing oil. the cause of my problem was my oil preasure sending unit behind the distibutor by the firewall.now my gauge reads 45-50 psi at idle and 60 plus at w/o throttle. hope this is usefull and hope that this helps you out the sending units are cheap and easy to istall.

 

I'm an idiot for not mentioning this in my original post... it is a new Autometer 0-100 psi gauge and corresponding sender. The old gauge did act similar too IIRC. I'm going to see if I can track down a mechanical gauge... I'm going to be pissed if my 4 month old sender from Autometer is AFU

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1984 z28 w/ a 357 cu in. monster engine which is looking like the posterchild for Edelbrock with the exception of the Holley 750vac... all the suspension stuff... 9-bolt posi disk is in...

-=ICON Motorsports=-

 

My car does the same thing as yours does. I've been told that SBCs have GREAT oiling systems and you only need 10psi per every 1000 RPM. I use Mobil 1 10W30 by the way.

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1987 Chevy Camaro IROC-Z
L98 TPI 350 (5.7L)
TH 700R-4 Transmission
Borg Warner 7.75" 9 Bolt Rear End with 2.77:1 Gears.

Current Mods: LT4 HOT Cam, Comp Cams 1.52:1 Roller Rocker Arms, Accel High Flow TPI Baseplate, Edelbrock TES 1 5/8" Headers, Catco 3" High-Flow Catalytic Converter, Hooker 3" Aerochamber Cat-Back System, Transgo Shift Kit, Performance Resource Chip, Accel Ignition, K&N Filters, Jet TPI Air Foil, All Free Mods, Falken ZIEX Z-Rated Tires.

Best ET: 14.32 @ 97.7mph
(corrected for elevation)