thunderstick

the 55 is a stock replacement, and a lot of times, the Mr.G spring is added to it for increased pressure... the 55A (supposedly for a Z-28) is roughly the same thing, but has increased pressure AND volume... so question would be, how suitable would the 55A be for a stock replacement, going back up with reworked heads and an LT4 hotcam?

and my next question would be how do you prime a new pump? i'm expecting my new cam today and the pump... thanks.

KAM

RB83L69

There is no particular benefit to the 55A, if the oiling system itself remains stock. The additional volume accomplishes nothing because the bearing clearances and similar things, which are what controls the actual flow of oil, remains the same.

Use the regular 55 and the Mr G spring. It costs less and does everything that needs to be done.

"Priming" the pump is unnecessary. The pump in one of these motors (unlike some other brands) is self-priming, because it's submerged in oil. There's no need to prime it when changing it, any more than there's a need to prime it when you change the oil. The exact same situation occurs at both times. Just fill the filter with oil before you put it on, and forget all this uselessness with drills and stuff, it is a complete waste of time.

thunderstick

well i've already bought the 55A, so no big deal there. yes, i fill the oil filter everytime i change oil, so do the same thing, and i'm good to go. thanks for the help.

KAM

RB83L69

The 55A won't hurt anything; it will just churn the oil around more than it really has to, and waste a little extra HP and wear out the dist gear a little faster. So, no real big deal, it's just not the best way to go.

If possible, why don't you just return it, and go to Auto Zone and get the 55, and the 55-S screen, and the MR G spring; and weldor braze or bolt on a brace, to hold the pickup securely to th epump.

Something else you can do that's actually beneficial, is to get rid of the stock oil pump drive rod, and instead, use the IS-55E, which has a metal collar instead of the plastic one.

Chris89GTA

iTrader: (2)

What exactly about the 55A causes this. I got one in the motor and it works fine. Didn't read all this stuff before I got it though.

I ended up w/ a Canton drive rod instead, so that should be better right?

RB83L69

A "high volume" pump won't actually deliver "higher volume" than a stock pump through the engine, unless there's larger clearances for more oil to flow through. In other words, if you take an engine with stock or near-stock bearing clearances and so forth, and put a stock-volume pump on it, and the oil pressure is (as an example) 55 psi; and you then change the oil pump to a "high volume" one, and the oil pressure is still 55 psi; then the exact same amount of oil will be flowing through the engine. The extra "volume" that the longer gears in the pump is moving, simply goes out the bypass, since after all, it's a positive-displacement type of pump, and any oil that it moves has to go somewhere. But, pressure times flow equals power; that means that if the pump is forcing more oil to flow somewhere, anywhere, whether through the engine or through the bypass, it's using more power. More power to the pump means less power to the wheels; and it means more load on the dist gear.

Bottom line is, if you're running a stock oil system, with no grooved main and rod bearings and gun-drilled rods and stuff like that, with stock clearances of .002" or so like you would with any kind of street motor, that high-volume pump is adding nothing to the total picture, and is merely using up power and causing extra wear without giving you any benefits in return. Not enough in the case of that particular pump to be a catastrophe or anything like that; it's just not the most efficient setup you could have. I wouldn't go jerking the motor out just to replace it, but if you happen to be in there again any time soon, you might want to consider changing it at that time.

Yes the Canton or ARP or Moroso drive rods are fine too, they just cost more.

thunderstick

yea, i can still return it all - still in the pkg's. thanks for the info.

KAM

Chris89GTA

iTrader: (2)

Thanks for the explaination RB. I kinda had an idea of what you were saying before, but that cleared it up. Makes total sense now...

I got the Canton drive for free so no change out my pocket for it.

snakeskinner

actually, without a higher capacity oil pan, you run the risk of starving the bearings for oil because the higher volume will pump all the oil to the top of the motor faster than it can return to the pan under certain conditions. My buddy wasn't aware of this in his LT1 and installed a 55A in his car. It would lose oil pressure under heavy pulls down the highway or at the track. I have not actually installed one personally but have many friends who have and all have removed them and reinstalled stock pumps. make SURE you watch your oil pressure if you've already installed one, it's likely to follow suit. Kyle

Chris89GTA

iTrader: (2)

I have blasted on it for extended periods with no problems yet. NO pressure drop to speak of... I will keep an eye on it though...

But I would think that going by what RB said, that if the clearances are stock, then the extra oil isn't going up to the top end of the motor, its just swirling around in the pan via the bypass. So the volume isn't going all the way up to the top.

Maybe my thinking is skewed??

snakeskinner

I've never heard the clearance arguement before so I don't know what that's about. None of the engines I've ever built for me or others have ever had any changes to the oiling system other than pumps. I don't know what type of changes you'd even make. Oil restrictors are popular for any street driven engine for the fact that there is already too much oil to the valvetrain in most engines. There are some, like the early 3.8 buicks, that do need more oiling but most don't need what they have. It is possible that you might ok, it's just that most cases have problems. One of my buddies pulled the valvecovers to try and adjust some rockers while the engine was running and it would shoot oil over the fenders out of the rockerarms, I think that's a little excessive and so did he so he went back to the stock pump. Kyle

RB83L69

What happens with a typical "high volume" pump, is that the pressure goes sky-high at high RPMs.

Remember, the bypass opens and allows oil to return to the pan when the set pressure is exceeded; but what's going to happen when the amount of oil that has to be moved is so huge that the little bitty hole in the bypass can't accomodate it all? When it reaches that point, the pressure in the system increases greatly because all of the oil that the pump is moving, can't squeeze through the bypass, and then the flow to the top of the engine DOES increase; and that's how you end up with all your oil in the valve covers.

The oil pump is a "constant displacement" type. That means, every time those gears spin, they move a certain amount of oil, period. Doesn't matter if they spin slow or fast; or how much pressure they're working into; the gears will move the oil, as long as the oil isn't forced back through them by the "head" pressure that it's working into. That oil that it's moving has to go somewhere. It's going to go into the bearings, or out the bypass, or through the lifters, or burst the filter, or something. The oil doesn't compress, and the pump doesn't stop pumping until some fairly enormous pressures are reached. The engine's oil flow requirements DO NOT change linearly with RPMs; the oil flow through the bearings is nearly constant, regardless of RPMs; so as the RPMs go up, the extra oil moved by the gears as they spin faster, has to go somewhere. The ideal situation is where the oil pump delivers exactly the amount that the engine needs, at its normal operating speed; any more than that, is just wasted power. That's pretty tough to achieve in the real world.