bryndalfly

I am going to be rebuilding my 1970 455 engine. It will be totally stock except for a M55HV oil pump. The question I have is, am I going to have problems using this high velocity pump with an all stock engine?
Thanks,
Jeff

joe_padavano

The "HV" stands for high VOLUME, not high velocity. You will be fine with that pump.

Kennybill

I would use a standard oil pump. Jmo Ken

bryndalfly

Thanks Joe. I read another forum (not an oldsmobile forum) that using an HV pump with a stock oil pan would cause major problems

It was early this morning and my brain wasn't quite functioning when u wrote velocity.

oldcutlass

It's not normally an issue, most use the stock pan with no problems.

joe_padavano

That's why you should come HERE.

Seriously, there's a lot of mis-information about high volume pumps sucking the pan dry. That's pure BS. Many here, myself included, have run the Mellings HV pump in a stock pan with no problems whatsoever.

Octania

Remember that the HV pump *can* deliver more oil to the engine.

This does not equate to *DOES* push more oil thru the engine.

Here's more:
https://classicoldsmobile.com/forums...-oil-pump.html

This needs to be a sticky, it comes up 2x a month.

Here's the other one:

https://classicoldsmobile.com/forums...-oil-pump.html

Octania Writes:

"The oil pump does NOT pump more oil THRU THE ENGINE because it [the pump] has more volume. Unless the pump cannot keep pace with flow- which is generally only at idle.

The pump (any pump) [almost] ALWAYS provides more flow than can be forced thru the engine. The remaining flow dumps over the bypass back to the pump inlet.

So, a pump 10,000x as large as the original will waste a lot of pressurized oil AT THE PUMP, but will not cause more oil to flow thru the engine, thereby "sucking the pan dry."

The pump output varies linearly [more or less] with RPM.
The oil passing thru the engine is [more or less] a steady rate, varying a little with the pressure developed by the pump, which at all speeds above idle should be the same 40 to 60 or whatever you set it to."

These three things should not be confused:
1) Oil flow thru the engine- the net output of the oil pump- which depends on oil viscosity, the pressure in the system, and the size of the hole [engine clearances].

2) Oil flow produced by the pump, much of which may never leave the pump assembly. This flow is on the output side of the pump's gears, and any amount in excess of that which goes thru the engine is dumped back to the pump inlet by way of the pressure relief valve- so it never really left the pump. The gear pump is [nearly] positive displacement. Therefore, output [to the relief valve] will vary linearly with speed, which is geared to the engine speed by way of the cam. So, at idle it produces perhaps less flow than the engine could pass, therefore the pressure is less than that required to open the bypass valve. But, at idle, the engine's needs are minimal, so all is well. At any speed above idle, any pump [and especially a HV pump] will produce more oil than can flow thru the engine, therefore the excess flow will be wasted, and directed back to the pump inlet. The relief valve maintains the pressure you asked it to, and all is well.

3) The flow thru the pump inlet screen should be the NET output of the oil pump- the same amount that was sent thru the engine by way of the filter and passages. This will in all cases except at idle be less or a lot less than the amount passing thru the oil pump, whether HV or Std Volume. Remember that some of the pump's output was NOT able to pass thru the engine, but was redirected to the pump inlet instead by the relief valve.

The flow into the oil pump is what may "suck the pan dry"... and THAT will depend on the oil flow thru the engine and the oil returning in a timely manner. It is conceivable that if the heads' return passages- which are not very steeply sloped- are plugged with old crud or pcs of valve seal, etc., and the engine is furiously pumping oil to the heads- such as at high RPM- then a sustained period of engine operation might result in insufficient oil supply in the pan. This was not, however, "caused by the use of a high volume oil pump."


keywords: HVOP excess flow