NOS327

iTrader: (30)

After a couple personal experiences with oil pumps, I'm debating which oil pump to use now.

Put a 10296 in my last lq4. Bearings were tight (.0015-ish, which is dandy per factory spec, .0009-.0022). Ran thin oil in the car, always idled around 35ish psi even on HOT days and on the bypass spring around 70psi in no time with throttle. After 2 years of beating the crap out of that motor, took it apart and everything looked fabulous.

Just built another iron block motor for a local that had .0025 rod and main bearing clearances which is more typical for higher power nitrous application, and per most people's suggestions just grabbed a GM 17801830 and put a port job and spring shim in it. Early indications are fairly low pressure. With Gibbs BR30 break in oil, it's only idling 15-17psi, cruising 2500-3000 RPM its making 30-35psi. I'm not overly concerned. After some break-in, he'll go to a thicker oil, which should improve his pressure.

Now my actual question, or thing that I would like validated please. Building an aluminum block engine for myself. Machine shop and I did some hot and cold testing to verify main bearing clearance growth with heat. My bearings are set up at .0025 right now and at operating temp will probably be more like .0030-.0032. I'd like to have more idle pressure that the motor above. So it go without saying that I need a higher volume pump to achieve this, right? 10296 no brainer? and/or run a 20-50 oil?

Thanks,
TJ

Exidous

iTrader: (11)

I would absolutely run the higher volume pump with the thicker oil. If pressure is too high you can go to a lighter oil then. With those clearances I'd want as much oil flowing through the motor as possible.

ss performance

iTrader: (17)

Higher volume or higher pressure pump?

NOS327

iTrader: (30)

Hi volume. The high pressure reference is in regard to the bypass pressure and has absolutely nothing to do with pressures at idle or anywhere below bypass.

4wheels

The 10296 is 18% higher displacement than the base LS1/LS6/LS2/LS3 pumps.
The 10355 is 33% higher displacement than the base pumps (and is the same dispacement as the cylinder deactivation equipped engine pumps).

A.R. Shale Targa

iTrader: (2)

To me an aluminum block should always have the mains in the .0012"-.0018"range....for a street/strip application. Bearing clearances should be set to dictate the pressures rather than oil viscosities and pumps. IMO a high volume pump belongs on a high rpm race only engine where you could care less about idle pressures. I've torn apart plenty of engines that people put HV pumps in and the mains are all copper from pumping the pan dry. They don't understand the fact that you can't pump more oil if you don't have more oil. Small block chevys have endured the test of time and no matter what generation we're talking about, they all have a darn good oiling system.

Exidous

iTrader: (11)

"Priority Main Oiling" I believe is the aftermarket term.

v8pwr

iTrader: (19)

Your main bearing clearances are too large. A high volume pump should be looked at when you need an increased supply of oil i.e. larger clearances. There are other areas that affect oil pressure due to additional clearance.

duffman_1

iTrader: (1)

Oil viscosity should be chosen based on expected operating temps. Bearing clearance is a balance between film thickness and pressure oil control. Having said that I wouldn't worry for a second running 15 psi at idle. I'd be more worried about having excessive bearing clearance that's puking a large amount of oil and really hurting your windage losses. I'll admit I have limited experience with big nitrous power though, so there likely isn't a way around the big clearances if that's what your alu block is intended for.