I agree with sharky...a high volume pump will help low rpm oil pressure, a high pressure pump will not, unless it is a high volume/high pressure.

The high volume has a physically larger pump body, and will move a larger mass of oil at a given speed than the stock pump will. This is irregardless as to what pressure regulation spring the pump has in it.

To make a high pressure pump, all you have to do is change the spring in the pump body. I stiffer spring will keep the bypass closed longer, and produce higher pressure.

So, it is possible to have a stock pump/stock pressure, high volume pump/stock pressure, stock pump/high pressure and a high volume pump high pressure.

My recommendation is a high volume pump/stock pressure spring, and use light oil ( Mobil-1 5w50 ).

As far as a rebuilt engine, most use builders generic bearing clearances...IE: .003". If you looked, you would have noticed the stock bearings you replaced were in odd sozes, like .0005 oversize...to tighten clearance. Chevy used about half the standard accepted rebuild clearance when building the L98, which is why they have good oil pressure with light oil at idle.

So, if you want 40-50 PSI at idle, your choice is to pull the main bearings and add odd size bearing shells, or put a high volume/stock pressure springs pump in, or both.

 

HAve you talked to your builder about the low pressure? I had a 383(450hp/450tq) in my 87Iroc.(had 1000 miles on the motor) It had low pressure after I went to Mobil 1. I drove it to Philly which is about a 2 hour drive. On the way home my pressure was only 8-10 in idle at about 900rpm. I made it home and was going to put in a new pump thinking the one installed was bad. I found copper in the oil, and found the main bearings scored. I pulled the motor and had to have the crank recut. HAve you changed the oil lately? Strain it to check for anything. If your oil pressure gets to low the fuel pump will shut off from the fuel pump/oil pressure switch.

 

i got the scoop on the driver... i'd forgotten that it has a plastic housing. some part of the housing commonly distorts, opening the housing to bore clearances into the over .005". if this clearance gets big enough, hot oil pressure will be pretty low.

it's pretty easy, just pull the intake, and remove the driver. take it with you to the dealer, along with a good set of calipers, and measure. you should be able to tell if that's a problem.

 

lt1s have an oil pressure switch that controls whether or not the engine will run? that's a new one to me. i know someone who's filter blew and the pump emptied the pan, and kept he driving for a few miles. the EFI was pretty content to run his engine as long he wanted!

 

Ok, thanks. I'm going to keep looking around in my service manual for this part. I'll call a few contacts I have at the dealer to see what they say as well.

 

I think I was wrong on that.. it's on the LS1 ?

 

some euro cars...


[Modified by MSR, 9:12 PM 6/2/2002]

 

L98's have this feature...but it didn't help out in my case. Live and learn I suppose. I was silly enough not to believe what my oil pressure was reading. I am surely going to remember it after this rebuild :rolleyes: Mine had less that 4 oil changes on it, so figure somewhere between 9K and 11K miles.

 

highopes, i'm confused... you say your L98 has that feature, but it didn't work because you chose to not believe the gauge? i guess some philosophers would say, "see, i told you so." ;)

 

The switch is not a garentee. It's turn off point can range from 2PSI to 12 PSI.
If you think about it...2PSI is NOT enough to save an engine...so damage from low pressure is always possible.

 

well, mine must be broken, then. i just experimented by disconnecting the oil pressure sending unit, and running the engine. it ran for 60 seconds, then i gave up and turned it back off so it wouldn't be too hot to reach and reconnect the sensor.

 

I ran my car yesterday for about an hour with the senor unhooked. I had a manual gauge hooked up where the electronic goes. It never turned it self off.

 

I called my machine shop today and verified that the clearances are .003". They also recommended switching to 15w50 with those clearances. He also said he recommended switching back to dino oil from synthetic. He wasn't very particular on synthetic. I'm going to try straight 15w50 first. Then I will go to dino.


[Modified by Glock'94, 2:04 AM 6/5/2002]

 

Since you are going back to Dino oil and you will be most likely be seeing fairly consistent warm temperatures for a while, try using a single weight oil. Try a straight 30 or 40 weight oil. You may find a pleasant difference in your oil pressure readings.

:seeya

 

Scorp...sounds like you got an 'old school' engine build. A lot of builders do this because with looser tolerances, less precision can be used in machining the crank throws. This is also evident in that the majority of turned cranks have tapered journals from the crank grinder not being dressed properly every time a crank is turned.

Don't go back to dyno oil. Use heavier synthetic oil. I think your best bet is to put in a high volume low pressure oil pump in it as well.

 

The oil pressure sensor you unhooked is just the gage sensor. The switch is located in a different place. On some, it is on the port just above the oil filter, on others it is in the port just next to the timing cover.

 

please read http://www.melling.com/highvol.html
http://www.melling.com/engoil.html
http://www.melling.com/miscon.html

-------------------------------------------------------------------------------- http://www.jegs.com/cgi-bin/ncommerc...63&prmenbr=361
pull the pan, remove the pump ,at this point youve got two choices
(1)install new high volume oil pump and pick-up or
(2), drive out the pin holding the old spring(its supposed to drive out in the upward direction,don,t lose the pin, and make sure the pressure relief piston moves freely, replace the old oil pressure bye pass spring with the new spring, make VERY SURE that the oil pump pickup on the pump is 1/2-3/8" off the bottom of the oil pan with the pan installed (use a lump of clay on the pick-up if nothing else to check this, once its correct braze the pickup to the pump, but do the measureing and brazeing before you replace the spring to prevent the heat from damageing the new spring)I would advise the new 1 piece plastic oil pan gaskets be used to reinstall the oil pan btw, install a new oil filter, and oil (optional but a great almost mandatory idea)and pre -prime the engines oil pump untill you get a pressure reading on the gauge. http://www.jegs.com/cgi-bin/ncommerc...01&prmenbr=361

personally the new high volume pump and pick-up is the easier route but of course the other way is cheaper

 

True. I guess I figured that when I bench tested it an saw a 8PSI switching point, I figured that it would have actually killed the pump had it gone lower than 8PSI. Don't get me wrong, it is an important lesson I learned.

My main reason for failure due to low pressure is 99% likely to be traced down to my oil pump pickup tube breaking the spot welds (pan smashing on low pavement) and ending up on the bottom of the pan on more than one occasion.

Like I said, live and learn.

 

Thanks grumpy... i think i'll go ahead and order a high volume pump. :cheers:

 

it's "GLOCK" :), but yes. Sounds like it was an "old school" like rebuild. The race shop that did it is a very reputable shop in OKC though.