low oil pressure at idle on 383 sbc

[1982chevyc10383]

hi im new on here and I cant seem to have anyone help me figure out my oil pressure problem on my 383 sbc in my 1982 c10. I just put this motor in about two months ago. im running 20/50w and at hot idle its running about 8-10 oil pressure. my dad bought this motor around two years ago unfinished. the pistions, rods, crank, and there bearings, and the cam bearings were installed and it came with a set of vortex heads that had work done to them. I bought it from my dad this summer and saved all my money to finsh it for my truck. its got a compcams 480. 480. lift roller rockers comp double roller timing chain and comp push rods. its got a high volume oil pump with the stock pan. im only seventeen and don't have a lot of money and this truck is my baby. thanks for time and help

[GM-power]

If you have access to a good oil pressure tester gauge hook it up and see what you have. Then you can eliminate a bad gauge. Any leaks? Why are you running such a thick oil in a relatively new engine?

[1982chevyc10383]

was recommended to by a friend that use to drag race. and just put a new oil pressure gauge on it. and there's no leaks that I can see. what weight would be better? and ill see if I can get my hands on a tester.

[manimal]

What is it hot at speed? Did you put it together or someone else? Was the oil pump pick up set at the right depth and tack welded to the housing? I too think 20/50 is too much unless you have MASSIVE bearing clearances. We need more info on the build.

[manimal]

And where are you taking the reading from?( on the block)

[GM-power]

Also does your oil pressure increase much as rpm go up? Like manimal said I doubt you have so much clearance to warrant that oil. And thick oil will make your pressure increase so if you ran 10w-30 it would be lower which would mean you got a problem. Like I said get a good oil pressure tester and make sure its not the gauge. Check to make sure your top end is oiling correctly to see if theres a pump issue.

[1982chevyc10383]

it runs around 190F and it gos up to around 30-35 psi at 40mph and its about 1750 rpms then idles just below 1000 rpms and drops to 10-8 psi when hot. I put the oil pump, cam, lifters, push rod, timming chain, and rockers in. the pistons, rods, crankshaft and their bearing were already installed before we got. we where told that it was a good motor and had no problems and that he was just going with a bbc and not the sbc. I had 10/40 in it but don't remember what the oil psi was. the pump I believe is the right depth and didn't tack weld it never heard of doing that. and its reading it from the back/top of the block behind the intake where they read on stock motors

[Corts60]

Is it an electrical sender? Might try replacing that if so. Least expensive thing to do. I agree with above about using a mechanical gauge installed directly to the engine to test pressure. Then you'll know if you have an internal problem or not.

[1982chevyc10383]

Alrighty I'll see if I can get hands on a tester and see what it says. It's got an aftermarket mechanical gauge on it. Thanks for the help i have more ideas on what to look at and look for. If it isn't the gauge and the tester reads low too. What should I do? Just drive it tell it gives? Or try and fix it? It's my only vehicle I have and like I said I don't really have a lot of money to but in it anymore cause I'm back in school now.

[clapage6]

sounds silly but what filter are you using? and is it new?

oil pressure when cold at start up?
oil pressure when at operating temp at idle = 8-10psi?
oil pressure @ ~1800rpm/40mph = 30-40psi?

I run 15w-40 rotella in my 454 with no issues all it does is Tow my toys out to the desert though.

[geezer#99]

If you got a mechanical gauge now another mechanical test gauge won't show any difference.
You got a big cam in it, how well does it idle?
If you smooth out the idle your oil pressure might come up.
What's your initial timing at?
Where's your vac advance hooked to? Manifold or ported?

[07XCSBZ71]

8-10psi per 1000 rpms is ok,not ideal,but ok, as long as it comes up with rpms, stays steady, and doesn't float around.

[Keating121]

Originally Posted by 1982chevyc10383

it runs around 190F and it gos up to around 30-35 psi at 40mph and its about 1750 rpms then idles just below 1000 rpms and drops to 10-8 psi when hot. ***** cut****** its reading it from the back/top of the block behind the intake where they read on stock motors

I have the same problem in my '70 383. Just started about a day ago. My oil level was low, so I added a quart but no change. Very strange!! Only owned the truck for a few months so don't know any details on the engine.

How long has your's been doing this 1982chevyc10383? Have you had any luck correcting the problem?
Have you tried changing the oil and/or filter yet?

[INSIDIOUS '86]

Lately I've noticed issues with melling pumps having the oil pump pressure bypass binding up at times. The more expensive line of oil pumps from melling don't seem to have this issue.

Another cause possibly is sometimes builders forget a threaded plug underneath the main thrust cap. This can cause a low pressure situation too.

[Sic73Cru]

I would check the bearing clearances. Not sure how much time or miles are on the motor but definitely oil is a serious issue to address. I had the same problem on a recent BBC build. When I put the bottom end together I did not mic the crank. Sure enough the crank was .030 under and I used .0000 bearings. Changed the bearings, Bang, done. Motor runs stout. No oiling problem.

Had the problem on a SBC 400ci long to short oiling problem caused a broken crank shaft and destroyed #8 cylinder. I had heard lower psi at idle is ok when warm, but this is surely a sign of a problem.

For me, to avoid any future problems and misreadings of a digital gauge, I have a mechanical hooked right up to the fitting at the oil filter. Just use about a 3 foot hose mount it right to the head. So if I see a low reading I go right to that gauge.

I hope you figure out the problem. Definitely something to corner for sure.

[Sic73Cru]

Originally Posted by INSIDIOUS '86

Lately I've noticed issues with melling pumps having the oil pump pressure bypass binding up at times. The more expensive line of oil pumps from melling don't seem to have this issue.

Another cause possibly is sometimes builders forget a threaded plug underneath the main thrust cap. This can cause a low pressure situation too.

Bypass is also another way I have heard to lose pressure... the plug too.

[ironroad9c1]

Originally Posted by 07XCSBZ71

8-10psi per 1000 rpms is ok,not ideal,but ok, as long as it comes up with rpms, stays steady, and doesn't float around.

Exactly , the old rule use to be 10psi for every 1,000 rpm.
also just run like 10-30, no need for a thick oil, and use only good wix or napa ,,car quest filters, never use a pos fram.
oil level doesn't affect oil pressure unless its so low it sucks the pan dry and starts sucking oil, then its bad news.

[Keating121]

Originally Posted by ironroad9c1

Exactly , the old rule use to be 10psi for every 1,000 rpm.
also just run like 10-30, no need for a thick oil, and use only good wix or napa ,,car quest filters, never use a pos fram.
oil level doesn't affect oil pressure unless its so low it sucks the pan dry and starts sucking oil, then its bad news.

Good info Ironroad, thanks.

[INSIDIOUS '86]

The fram filters are ok but limeted in application. The issue with these filters are high rpm motors and motors with hv oil pumps. Also oils like synthetic can go extended intervals but a lot of filters do not. This is where extended mile filters come in handy. And even then they will only last 6months reliably being oil saturated.

If anything I would pull the motor and check everything like bearing clearances and the pump to make sure. It's time consuming and a pain in the butt. It that or risk your rotating assembly getting destroyed. And that's an even bigger pain

[andrewmp6]

I'm thinking bad oil filter or maybe oil pump pickup tube is too close to the pan maybe.

[Jake Wade]

Sounds like loose clearances to me. I would not be comfortable with those readings and 20w50 oil.

[Krwright]

Originally Posted by Jake Wade

Sounds like loose clearances to me. I would not be comfortable with those readings and 20w50 oil.

X2. He's probably under 5 psi with 10/30. Pull the pan and check bearings and replace them and the pump.

[BigBlocksRule]

Toss the junk cardboard Fram filter and get a Wix.
If you tear it down, double check those cam bearings (not just rods and mains) and the drive-in plug in the back of the block.

[bnoon]

I would not be worried about 10 psi under 1000 RPM idle on an aftermarket high volume pump. High volume pumps tend to be race ready for constant high RPM use and really don't come into their efficiency range until higher RPMs. Drop the 20/50 oil unless you have a rattle from loose clearances when using a 5/30, 5/40, 10/30, 10/40 oils first. 20/50 is fine for a race vehicle, but has no place on a properly built/assembled street engine because again, thicker oils are needed for sustained high RPM of a race engine (or really loose clearances of either an OLD engine with really high miles or a loosely assembled race engine).