Melling hv pump

[rigid1]

Didn't want to hijack another thread ..

06 Denali drove 20 miles. Started again and no OP , bell going off and started to chatter in the upper end. Got a little louder so hauled it home. Had an o ring issue two years ago that did not get caught in time so this is a replacement with supposedly 90k at that time. Suspected an o ring here and that is not the case.
At this point.

Oil ring and pick tube are fine. Both valve covers off and no apparent lifter problems. # 4 main bearing cap pulled and bearing looks new. Just took oil pump off and no broken gears. Not sure on how to check the rest of the pump.

Here is the question. I have a brand new HV pump from the last episode.. long story. I would like to put it on put things together. What scares me a little is that I have had a mechanic say he has seen this pump take out main bearings I guess with too much pressure. It has the spring in it that it came with. Not sure I can find the other one, but could order one I would think. when this engine was put in It ran at about 30psi down the hwy. In thinking back a couple weeks ago I thought the gauged jumped around a couple times and was lower than normal. Do I change the spring or am I worried about nothing?

Thank you

 

[iamdub]

Didn't want to hijack another thread ..

06 Denali drove 20 miles. Started again and no OP , bell going off and started to chatter in the upper end. Got a little louder so hauled it home. Had an o ring issue two years ago that did not get caught in time so this is a replacement with supposedly 90k at that time. Suspected an o ring here and that is not the case.
At this point.

Oil ring and pick tube are fine. Both valve covers off and no apparent lifter problems. # 4 main bearing cap pulled and bearing looks new. Just took oil pump off and no broken gears. Not sure on how to check the rest of the pump.

Here is the question. I have a brand new HV pump from the last episode.. long story. I would like to put it on put things together. What scares me a little is that I have had a mechanic say he has seen this pump take out main bearings I guess with too much pressure. It has the spring in it that it came with. Not sure I can find the other one, but could order one I would think. when this engine was put in It ran at about 30psi down the hwy. In thinking back a couple weeks ago I thought the gauged jumped around a couple times and was lower than normal. Do I change the spring or am I worried about nothing?

Thank you

I put a HV Melling in my brother's truck that lost almost all pressure due to a clogged pickup screen (heavily sludged motor), so I don't know what pressure it would've ran at had the screen not been clogged. I used the lower pressure spring (Green? Blue?) in place of the red spring and I'm glad I did cuz it nearly pegs the gauge at 80 when revved to redline. At normal driving RPMs it stays around 35-50 psi and steady 40 psi when cruising at 60 (1500 RPM).

If I were in your shoes, I'd use a lower pressure spring, maybe even the one from your current pump. You'll get enough of a bump in pressure just from the extra volume that pump produces. I've never shopped for just a spring but they may be available. Or, if you're on LS1tech, maybe see if someone has the low pressure spring leftover from their HP or HV pump installation.

 

[rigid1]

I forgot to add.. it is the HV295 not the 10296

Thank you

 

[SnowDrifter]

Have the same pump in my rig with the high pressure spring. For your oiling system issues, verify that your pickup tube is in good condition, and if you're feeling so inclined - take apart the oil pump all the way. Inspect the rotors for cavitation damage and the relief piston for any scarring that would indicate binding in the bore. The latter of which were the issues I was having.

I'd question that mechanic. I looked into the pressure thing pretty extensively during my own research. Inevitably, all the forums are jabbering on and on and on but no one could produce a single example of that failure scenario.

Logically, I can't comprehend how it would cause a bearing failure. An oil pump is designed to keep oil flow to bearings/lifters such that there is always a film of oil. In a rotating assembly such as a rod bearing, the bearing caps and interior crankshaft rotate on an off-center axis. It's fractional thousandths of an inch, but that does exist.



As far as steps go, that motion carries oil throughout the bearing, and the oil pump's job is to provide adequate flow to replenish that cushion of oil when the crankshaft sweeps away from the oiling hole (cavitation region). Also of note, that pressure wave and point of high pressure interference where the crank is closest to the bearing is around - denoted Pmax in the second diagram, is going to be in the several thousand PSI range. So the difference between 60-70psi with a stock oil pump, and a 100-120psi with a high volume/high pressure pump is negligible, to say the least.

Fluid cutting tools such as water jets operate in the many ten thousand PSI range (~60k) and use an abrasive to wear away material.

Now there might be a theoretical argument to be made here that a higher flow oil pump could reduce cavitation but I don't think that's really helpful in answering the question.



Because pressure and volume in this application are related - you're pushing fluid through a relatively fixed orifice. Higher volume would necessitate higher pressure, and vice-versa. You could attain higher pressure by using a thicker fluid, but that would come at the expense of flow. Ponder the diagrams for a minute and you'll see why I'm generally against thicker oil in an otherwise healthy engine. Cutting down on flow to attain a higher pressure number isn't really helpful to anything.

Now as far as how the oil pump operates: The bypass valve isn't binary. It pushes against a linear rate spring. It'll start to bypass a little, then as pressure builds, bypass more. That's how these rigs attain 30-35psi at idle but 40-45 when cruising, despite being at 2-3x the rotational speed when idle. It creates a nonlinear pressure relationship that allows adequate pressure/flow to inflate lifters and feed bearings in an idle scenario, but without creating a 500+psi overpressure scenario (which would blow apart the oiling channels in your block, filter, and oil pan gasket) if you were to redline the motor.

It's for that reason that you'll see an increase in pressure across the board, even when using the stock pressure spring in a high flow pump.


For other considerations: because you're pumping more fluid at a higher pressure, I'd look into using a "long" filter and a quality one. Personally I use an amsoil eao64 or fram ph3675. Cross reference that to your own choices. Both flow well and have more filtering media than stock, and have a nice thick casing that I'm not worried about blowing apart when I take the engine to redline (which for me generates about 115psi oil pressure). There's a benefit to using a longer filter here in that higher flow creates a greater pressure delta across the filter media. Exceed that too much and the filter bypass valve will open and allow some unfiltered oil to make it's way through the engine. Use a tiny filter - that valve could be open more often than not, and you're potentially cycling a lot of contaminants through your system.

p.s. there seems to be other info online about these causing oil starvation. I've yet to see that in my rig even under extended 4k rpm use when going up mountain passes. The only time I was able to find that happening was for track use where the g-forces in turns physically disallow the oil to drain away from the heads until the turn is completed.

Uhhhh.... That pretty much wraps up my thoughts.

tl;dr pressures offered by a high flow oil pump aren't damaging to a bearing. Use a longer filter with more media, don't cheap out on filters. Seems to be an old wives tale that's been recycled around the internet for god knows why. You'll blow out your oil filter before you can produce enough pressure to harm anything in the engine.

 

[rigid1]

Thank you for the information.I read it last night and then again twice this morning. I will admit it did not understand all of it! I did put the pump on tonight as is. Your last paragraph makes all the sense in the world and is something I needed reminded of.
Raced circle track cars for many years. Did not have time to get an engine put together after hurting one on a Friday night. Found a nice new short block and got it in the car Saturday. Lost it that night. I had bought a Fram filter from walmart. It was short and a passenger car filter to boot. Burned up the bottom end. Cut it open and it was so tight oil almost did not come out. It did its job. I bought the wrong filter. From then on it was Wix Racing filters only. Not cheap but then engines are not either.

One last question. We normally use 5w30 as it shows. What would you reccomend with this pump.

Thank you

 

[SnowDrifter]

Thank you for the information.I read it last night and then again twice this morning. I will admit it did not understand all of it! I did put the pump on tonight as is. Your last paragraph makes all the sense in the world and is something I needed reminded of.
Raced circle track cars for many years. Did not have time to get an engine put together after hurting one on a Friday night. Found a nice new short block and got it in the car Saturday. Lost it that night. I had bought a Fram filter from walmart. It was short and a passenger car filter to boot. Burned up the bottom end. Cut it open and it was so tight oil almost did not come out. It did its job. I bought the wrong filter. From then on it was Wix Racing filters only. Not cheap but then engines are not either.

One last question. We normally use 5w30 as it shows. What would you reccomend with this pump.

Thank you

In mine, I run a 0w30 or 0w40, M1 0w30 ESP, or Castrol 0w40 Euro Formula. I've favored 0wXX in every vehicle I've owned ever, so don't read that as a requirement or recommendation on account of the oil pump change. I switched to the latter as the mobil 1 was becoming difficult to get at a reasonable price. They're not too far off as far as viscosity goes. The mobil 1 was a thick 30, the castol is a thin 40. Only a couple PSI difference between 'em at a hot idle. The mobil 1 was 45-46ish if memory serves. The castrol is 49.

I've not played with different viscosities. Might entertain that in 10k mi or so. Doesn't make sense to start sampling oil with new hard parts and gaskets in the engine. Would need to wait for wear metals to level out and fully break in, which takes a couple ten thousand miles. Sampling now would give numbers but nothing useful as I'd be in the middle of a down trend anyway.


I don't know enough about these engines to know if it might be appropriate to run an Xw20. Theoretically it would be a non issue on the bearings on account of greater flow. But then you have considerations for the hydraulic lifters and their bleed off rate, as well as the timing chain.

You should, on paper, be able to run an Xw40 and attain similar flow rates to the 5w30 you were running prior. But unless you're in a high load / high temp situation such as towing that would heat thin the oil, or you have a bearing or 2 that's out of tolerance I'm not sure that would be appropriate either. Cam bearings are also a consideration for going thicker as these aren't pinned(press fit into a hole) - not sure the effect of low temp(high viscosity) drag on the propensity of these rigs to chuck a cam bearing. Might be worth doing some reading on.

Of course, that's just speculative. I have no numbers to back up anything, and won't for another year or two. The only thing I've discovered in my previous research, are folks spinning cam bearings in new rebuilds; the finding being that they were not line boring said bearings. Wasn't able to make any determination about oil viscosity being a factor.

I'd breathe easy and run your regular oil. Like I mentioned I've not experienced any drainback issues but if you need/want peace of mind, 2 things:

1. You have an oil level sensor that will trigger if the pan level drops too low, prior to running the pickup dry and incurring any engine damage

2. You can run 7 quarts in these rigs without any frothing / windage issues. You'll need around 7 to get it to fill anyway after having the pan down and pump off

 

[SnowDrifter]

Oh and because I know it's easy to lose track in the middle of projects; don't forget to prime the oil pump

Also; you can turn the key on for 3-4 seconds, push the gas pedal to the floor for another 3-4 seconds, then with the gas to the floor, crank it. Engine won't fire but it will crank. Can use it to get some oil through the system before you let it fire over