Oil Pressure upgrade

[DerekTheGreat]

I'm a fan of Smokey, too. Never tried ProLong, though.

Sounds like a sex aid...

My '88 K1500 takes a certain part number of sending unit. They last a few years. I'm on my fourth one now. Every one reads a little different when new. When they fail--which as I said is fairly frequently--they can read too high, too low, or just plain leak.

There's a bunch of companies that sell this sending unit, but far as I can tell, only one company making them, and then packaging 'em in different boxes. The distinguishing feature is a stripe of green paint near the electrical terminal. They're junk, but what can you do except buy from a "lifetime warranty" brand and keep the receipt.

http://www.automotiveforums.com/vbulletin/showthread.php?t=1136624

Can confirm. I think I'm on my third and this one is starting to give me the fits. To me, its Ford style now- just an dummy light in gage form: If it moves to the right and I've got no noise- Oil pressure, yay!

 

[Schurkey]

At what psi does the bypass valve open.

Do you mean the pressure relief valve? Depends on the spring installed behind the pressure relief valve. The pump I linked-to should have a 52 psi spring installed, and a 60 psi spring in the box for the consumer to install if desired. Melling sells a 70 psi spring pack under p/n 77070.

Note that these are "Big Block" springs because that's a "big block" pump, that happens to fit (with modifications to the windage tray, and the correct pickup tube) on a small-block.

At what Engine rpm does it achieve psi to open the bypass valve.

Depends on how loose the bearings are, how much the lifters flow, etc. A tight engine will open the pressure relief valve at lower rpm than one with loose clearances. An engine with a high-volume pump will open the relief valve at a lower rpm than one with a low-volume pump.

Does indicated pressure remain constant after reaching bypass valve opening pressure.

Within the flow limits of the pressure relief valve, yes. Cold, thick oil can't pass through the pressure relief easily, so cold oil pressure tends to be high. Beyond that, it'll depend on pump volume, engine oil flow demand, RPM, oil viscosity, etc.

 

[L31MaxExpress]

Standard volume high pressure big block pump takes less power to spin than a high volume small block pump.

 

[Schurkey]

...and the Big-block pump has more pump gear teeth, which--supposedly--reduces spark-scatter.



Power required to spin might depend on "which" "High-volume" small-block pump we're comparing to. There's pumps with +25% capacity, and pumps with +10% capacity. And of course, a higher-pressure spring in the relief valve assembly would make a difference, too. Higher pressure would require more power, as would higher volume.

I don't know how the "standard" BBC pump volume compares to a "standard", +10%, or +25% small-block pump. I've always believed that the BBC pump had HUGE volume compared to small-block...but I've never confirmed it.

Time to send an e-mail to Melling, I guess.

 

[thinger2]

20 psi at hot idle is just fine.
But, the factory oil pressure gauge is pretty much worthless.
Stick a mechanical gauge on it to see whats really going on.
Using a high volume pump wont really hurt an sbc.
A lot of people will claim that it pumps all the oil to the heads and starves the mains.
That is true on Olds engines and some Buicks but not a problem on a stock sbc.
They will also claim that it will shred the distributor gear. Thats more of a Ford problem.
But, if you have a stock build with stock clearences, the high volume isnt worth the money on a new build.
If you built it with large clearences than by all means get the high volume.
But be carefull about which one you buy and check the pump rotor clearence before you install it.
The aftermarket ones are all over the place.
Have you readjusted the valve lash since the rebuild?
I think I would do that and change the oil and see what happens.
But, like everyone has mentioned
lifters have some serious quality problems these days.
The only other things that pop to mind are if you still have the factory oil cooler, make sure it isnt leaking.
And look at the oil pressure switch fitting at the back of the manifold to make sure it isnt leaking or loose.

 

[L31MaxExpress]

20 psi at hot idle is just fine.
But, the factory oil pressure gauge is pretty much worthless.
Stick a mechanical gauge on it to see whats really going on.
Using a high volume pump wont really hurt an sbc.
A lot of people will claim that it pumps all the oil to the heads and starves the mains.
That is true on Olds engines and some Buicks but not a problem on a stock sbc.
They will also claim that it will shred the distributor gear. Thats more of a Ford problem.
But, if you have a stock build with stock clearences, the high volume isnt worth the money on a new build.
If you built it with large clearences than by all means get the high volume.
But be carefull about which one you buy and check the pump rotor clearence before you install it.
The aftermarket ones are all over the place.
Have you readjusted the valve lash since the rebuild?
I think I would do that and change the oil and see what happens.
But, like everyone has mentioned
lifters have some serious quality problems these days.
The only other things that pop to mind are if you still have the factory oil cooler, make sure it isnt leaking.
And look at the oil pressure switch fitting at the back of the manifold to make sure it isnt leaking or loose.

Stock volume big block pump is worth it on even a stock spec build. The bypass is designed better and the increased tooth count makes it turn more smoothly as well as flow oil more smoothly. Zero need to worry about shreding the drive gear either as the big block uses the same gear as a small block. Only trick is to run the steel sleeved shaft and get an oil pump stud rather than a bolt. My windage tray needed a little ground off for clearance as well. Used a big block bolt-on pickup to match the pan depth

 

[b454rat]

Of all the engines I built over the years, not 1 was starved of oil. I always used Mellings high volume, not pressure, and worked great. High volume will move the oil faster to the lifters, rockers, etc. My Tahoe has 210k on it, and according to the gauge is lil over 20lbs hot. Driving is lil under 60. As long as your getting oil pressure, I wouldn't worry too much bout it.

 

[Erik the Awful]

I put a standard Melling replacement in my motor. My factory gauge reads 60psi at idle. Not sure what's going on there, but it runs great. Next oil change I'll probably swap down to 5w20 oil. I wouldn't bother with a high-volume pump.

 

[L31MaxExpress]

Mine idles at 40 psi and maxes out at 70 psi at about 2,000 rpm. 5w30 synthetic. In a low-end grunt engine that sees alot of towing the added oil pressure is just more flow to the bearings.

That being said I had a 305 that had 10 psi at hot idle. 60+ at higher rpm. Ran just fine.

 

[stutaeng]

I forgot what OP was asking now...

But isn't oil pressure a function of bearing clearances? I'm assuming OP checked those? And it doesn't sound like there is actually low oil pressure to begin with by the information given.

Isn't a high pressure pump for an engine with tighter clearances? But for a given bearing clearance and RPM, increasing the fluid flow will obviously also increase the oil pressure...if I recall correctly from basic fluid mechanics theory.

One of my trucks with the 4.3 had low oil pressure (6 psig at the oil pressure sender screw point. The dash was negative, LOL and check guages illuminated.) My buddy has the same engine on his truck and he kept trying to argue with me that I needed a new oil pump. I've explained to him countless times it's my bearing clearances becoming loose... basically a worn engine...but he still thinks it's an oil pump problem! Engine still ran fine when I pulled it.