chr45gt2

I'm doing my HCI swap in the upcoming week on my 01 SS with 153k. I have a melling high pressure oil pump that I bought to use on another engine that I'm no longer building. Should I swap out the pump while I'm in there? The car has great oil pressure, it sits at just under 40psi at hot idle and rises nicely with RPM. I'd rather not swap it out unless I have to.

G Atsma

The only thing that says "change the pump" is the mileage (153k) on the engine. But it seems the present pump is healthy, FOR NOW. What about the next 50k miles? As long as you are in there, AND you have the pump bought and paid for, put it in. Just for peace of mind if nothing else.

99Silver6.0

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1FastBrick

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If you want to change the pump that's fine, but no need to put a high pressure one in there.

G Atsma

He already has it, and a high-mileage engine to put it in. The high pressure aspect will do no harm at all.

Che70velle

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z28241

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OP have you had this car since day 1? I wouldnt be surprised if the engine dont already have a high volume oil pump, PSI sounds stout given the info..

1FastBrick

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Agreed. No need to over complicate the situation.

There is no benefit in running a High Pressure pump in an engine with stock clearances regardless of miles. As mentioned it robs power.

Mileage does not effect bearing clearances. Maintenance practices or lack there of can.

G Atsma

A high pressure pump is high pressure ONLY at the highest pressure seen. The pressure is no higher than normal any time it's not max pressure. It just has a higher bypass pressure. It only robs power at pressures higher than those seen with a standard pump. Day to day driving will be no different. If anything a high volume pump will be the constant power robber as it's pumping more oil all the time.

joejamesatou

I replaced mine at 215k miles when I did the heads and timing chain. The pump cost less than $70 online. Stock volume and pressure. Cheap insurance with the tinint chain.

Che70velle

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G Atsma

How, with two pumps of the same volume, can one make more pressure at idle or other speeds BEFORE the relief valve pops? It's the relief valve that determines peak pressure in a pump. Actual pressure is determined by the resistance to flow. If two identical pumps in two identical engines are pumping oil at pressure BELOW the relief popping point, both will deliver the same pressure reading, because the situations are identical. Where it changes is when the relief in the standard pressure pump pops at a pressure lower than the relief in the higher pressure pump. It's a simple hydraulic system. Pressure is determined by resistance to flow. Work it too hard and something blows from too-high a pressure. That's why relief valves exist. A high pressure pump has a higher relief pressure point either by way of a stiffer spring or shimming up the one already there..
Long story short, High volume pumps are simply larger pumps with a standard relief valve. High pressure pumps are standard pumps with a stiffer or shimmed relief valve spring. AND high volume/high pressure pumps are larger pumps with the stiffer/shimmed spring.

Che70velle

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G Atsma

Good example- Look at a Melling standard pump and a high pressure pump. Check the parts. The ONLY difference between the two is the relief valve has a stiffer spring in the high pressure pump. The castings are the same. And they're machined the same. That's why they cost the same. High volume pumps are bigger pumps, thereby costing more.
How, with two identically sized pumps, can one develop more pressure than the other before popping their respective relief valves? Can't happen. I studied hydraulic system theory and this is how it has to happen. Pressure is determined by resistance, and two identical volumes pumping thru two identical engines will develop identical pressures, UNTIL reaching the maximum pressures determined by their respective relief valves.
A higher VOLUME pump WILL develop higher pressures thru the range because more oil flow develops higher resistance, and thereby higher pressure, until the pressure ceiling determined by the relief valve.

tech@WS6store

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Always pet the puppy and always change the pump. Always use high pressure and stay away from high volume.

Che70velle

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Che70velle

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Stampede4ever

Has there been many pump failures? I pulled mine apart and checked the clearances, everything was well in spec. I don't know the mileage of my ls, but I bet money its will over 200,000 easy, came out of a box truck, that runs none stop.

Stampede.

TA_Freak

Change the pump, But do it right .. drop the oil pan, then you shouldn't have any issues with the o-ring. Since you're gonna drop the k-member, change your motor mounts while your there if you haven't before. It all makes sense - since you are there. I did mine several thousand miles ago and I now have 341,000 miles on it. Drives at 60psi and idles at 30.

RockinWs6

I changed the stock oil pump at 155k, looked like new inside no wear what so ever. With the new Melling stock replacement 10295 pump oil pressure is about 5 psi less @ 2500 rpm and about he same as stock WOT 5k rpm. For me replacing the pump was nothing more than a complete waste of time and money.