20 psi for oil?

[shadowwalker_02]

I remember reading a thread where ryoken said you need 10psi per 1000 rpm. I don't know if that was for a sbc or bbc? I searched but I couldn't find an answer. After starting the 468 and keeping it in between 2-3k rpm for cam break in I noticed while idling around 1100rpm or so the oil psi drops to 20. Between 2-3k rpm the oil psi is around 39-40. Is this normal for a bbc after a rebuild? I know I'm a bit paranoid with this motor but I want to make sure.

The other thing I noticed after shutting it off was the fact that the fuel in the fuel filter had alot of air bubbles coming up through the line. I know I don't have a return line on it so is this normal? I've never encountered a situation like this before.

I think after it cools down I'll run it for another 5-10 minutes and then hopefully I can maybe take it around the block. Assuming I can keep the headers and exhaust from melting crap and starting more fires. The S bends are allready turning a blueish color.

 

[Fordum]

That sounds too low for a rebuilt engine. But, if its the factory electric gauge, don't trust it.
Probably most of them are good, but they were not manufactured as precision devices, plus the sender resistor can wear out.

You need to get a good mechanical gauge.

 

[shadowwalker_02]

Thats with a sunpro mechanical oil gauge. The factory one doesn't work so I hooked that one up and it doesn't leak. I still have to do one more oil change so it might be all the crap and lube still in there. If it stays at 20 psi at idle is there anything I can do to improve the psi? I did read about greg72 saying some BBC blocks suck at oiling the top end but could there be any other causes except the pickup screen falling off or not on right?

 

[gonefishin]

i have never rebuilt a bbc but did you forget a oil plug by some chance causing an internal oil leak and did you put a standard volume or high volume oil pump

 

[Fordum]

There are lots of reasons why a rebuilt engine has low oil pressure, none of them good.
The pressure relief valve in the pump could be bad, the pickup falling off will often give intermittent pressure as it sucks air.

But the main reason is too much clearance somewhere. Cam bearings, rod or main bearings.
Usually the rod or main will make a noise if its so loose to kill oil pressure, but not always.
A cam bearing will not make a sound, just dump the oil pressure.

 

[ryoken]

what weight oil?

 

[shadowwalker_02]

I use 10-30w castrol with a napa gold filter.

The oil pump is stock and I'm pretty sure I didn't forget an oil plug.

I'm not hearing any unusual noises coming from the motor. The crank and main bearings are .010 over so it may be that but again im not sure. When I do the oil change I'll pull the pan off and see if I cant see anything out of whack.

 

[Stomis]

I use 10-30w castrol with a napa gold filter.

The oil pump is stock and I'm pretty sure I didn't forget an oil plug.

I'm not hearing any unusual noises coming from the motor. The crank and main bearings are .010 over so it may be that but again im not sure. When I do the oil change I'll pull the pan off and see if I cant see anything out of whack.

Whats your bearing clearance? If you went loose on the rebuild and didnt put in a high volume pump that could be your problem.

 

[gonefishin]

i would plastigauge the rod and mains while you are in that far

 

[shadowwalker_02]

rod and mains are 0.010 over as well.

I have been thinking of putting a high volume oil pump in and I think that may be what my issue is. Melling has some for around 100 bucks but does anyone have any preference on HV oil pumps?

 

[Fordum]

You should not need a high volume oil pump on a stock engine.
All its going to do is cause problems, and increased distributor gear wear.

It should not matter what the crank was turned down to as long as you used the correct bearings.
If its turned down to .010 undersize, then you use .010 bearings which are that much bigger to make up for the undersize.
If you used stock bearings on a undersize crank then that would cause the problem, but you said you used the correct bearings.

 

[shadowwalker_02]

You should not need a high volume oil pump on a stock engine.
All its going to do is cause problems, and increased distributor gear wear.

It should not matter what the crank was turned down to as long as you used the correct bearings.
If its turned down to .010 undersize, then you use .010 bearings which are that much bigger to make up for the undersize.
If you used stock bearings on a undersize crank then that would cause the problem, but you said you used the correct bearings.

I wouldn't say it is stock with the .060 overbore but its kind of close to stock. And yes I have the right bearings, I actually ordered those myself from a parts place here in town that actually knows there s***. The distributor is one of those msd street fire ones with some new type of gear on it. I'll have to go reread the box but i remember looking at it.

 

[K10 KRAWLER]

The last BBC that I swapped into my rig did the same thing. It was rebuilt at a good shop. after a few weeks of driving it stopped doing it. what caused it, I don't know

 

[Fordum]

Hey, you mentioned grease and lube.
Pull the fitting off the engine and check to see if the fitting or tube going to the gauge has a bunch of gunk in it.

You might take it loose from both ends and blow through it.

And put a rag over the fitting in the engine, don't turn on the ignition, and bump it over with the starter to blow out anything that might be in the hole.

Just don't let it crank. You don't need a gusher.

 

[ryoken]

I use 10-30w castrol with a napa gold filter.

The oil pump is stock and I'm pretty sure I didn't forget an oil plug.

I'm not hearing any unusual noises coming from the motor. The crank and main bearings are .010 over so it may be that but again im not sure. When I do the oil change I'll pull the pan off and see if I cant see anything out of whack.

how long did you run it? it is a bit unusual to be low on start-up, and improve later, it's usually vice-versa, being the motor is tight on start up...

thats a bit heavy on the break-in rpm's imo.. i generally vary it from 1500 to 2000..

I would consider changing the oil and filter now that it's had it's break-in, it never hurts and it's cheap... maybe bumping the oil up a bit, to maybe a 15-40 and see if it improves..

it's not horrible, but it's not great.. i usually like to see em idleing with about 35, 40 lbs.. that 10 psi per 1000 rpm's is a number thrown around as a minimum a motor needs... ya certainly don't want to see 10 psi at idle...


how much does it change when revved?

 

[shadowwalker_02]

all total is has about around 30 minutes run time on it so far. When the motors cold is usually runs at 60 psi when running at 2k rpm. when it gets warm its around 40 psi at around 2k+rpm. At idle when warm its right above 20. I'll change the filter and see if that helps. If nothing else I'll switch to the 15-40w. I'll make sure the gauge isn't gummed up and see where that gets me.

Edit: at first start up 850 rpms the oil is right at 45 psi.

 

[Chevy305]

Ya I had that problem with the break in of my engine. Great pressure durring the break in period then afterwards I got hardly anything. I changed the oil and put a different gauge on and boom problems solved. I did upgrade to VR1 20w50 at the same time but the change in viscosity wouldn't account for the amount of change I saw. BTW I run that thick of oil because I have relatively loose bearings.

 

[shadowwalker_02]

I think im going to switch to a bit heavier weight oil maybe 15-40. I still wanna drop the pan and check the oil pump and make sure everything is still attached.Though At this point I wont be able to do much of anything till I get paid again. Damn sewer line was backed up and had to get someone to run an auger through it, what a sh**ty day. Had to spend my truck money on the sewer. Being a homeowner is challenging at times. Not to mention a pet owner as well.