Hi guys, I'm about to change the oil pan gasket on the Vette and was thinking about changing the oil pump while I'm at it. I was looking at the Melling pump part#M-55HV, which is suppose to be a high volume/pressure pump. Have any of you guys used this pump? Do you guys have any other recommendations for me? I work at O'Reilly Auto Parts and can get this pump along with the shaft. What do you guys think?

 

Not sure about the rest of your engine specs..but you likely don't need the HV pump unless oil pressure was low in the past. If you're going to change it I'd get the Z-28 pump (stock pump with high pressure spring). Biggest thing is to make sure pickup tube is secure.

You could just put a new $3 Hp spring in the pump you have and tack weld the pickup and be good to go!

JIM

 

Do you have the part number for that spring/pump, A link?

 

Would that pump damage the engine in any way? I found these springs, which would you guys recommend?

http://www.summitracing.com/search/P...4/?Ns=Rank|Asc

 

If you have adequate oil pressure at hot idle you won't benefit from the pump or the spring.

You should know that the spring only limits the max the pressure will hit and most engines only hit the max if you rev them up when the oil is cold and thick. It will not change your oil pressure at idle or cruise or through most of the operating range most of the time.

A high volume pump will increase your oil pressure at idle and through the entire operating range with probably the same high limit as you now have. You will not hurt the engine by having either, but if the engine has normal internal clearances and good oil pressure now adding a high volume pump will do nothing for you and will rob engine power unnecessarily. It takes more power to drive a pump pushing 50 psi than one pushing 30 psi. If it's not doing anything for you, why give away the power. The increase in power it takes to provide the additional pressure is probably greater than what it takes to drive the smog pumps everyone is so eager to remove.

Steve g

 

I forgot to mention that I will be doing some auto-X with this car and it will have a cam and maybe some aluminum heads.

 

If you are using the stock Vet oilpan a High volume pump will hurt you more than help you. With a high volume pump it will more than likely Aerate the oil when used in Auto-X or track day events. The Z-28 pump is a good upgrade for a stock oiling system and will not suck the oilpan dry.

A High volume pump is just that. More volume=more oil moved. The gear sets are taller by as much as 3/8" the pickup tube has a larger ID 3/4" vs 5/8." Unless your running an oil cooler and external oil fiter you really don't need it.

The SBC has a very good oil system to start with.

 

Be careful of any new purchase - Melling (I hear at the request of GM) lightened their oil pumps a few years back. I've seen a few broken ones, not pretty. They still make a beefy one, you'll need to do a search to find out which one to avoid.
Oil pumps rarely wear out. Take yours apart and check it out, it's probably fine. You might add a windage tray for the auto cross, maybe even a trick pan. But your oil pump is probably fine.

 

I agree. Keeping the oil in the pan and around the pickup tube while auto-crossing is most important so a windage tray (at least) is needed. To get the full benefit of a high-end pump requires opening up the oil return passages in the block and heads to make sure the oil gets back to the pan after being pumped up into the rocker cover and lifter valley. Plus it puts more strain on the distributor drive gear. A Z/28-style pump works best for all but the most radical setups.

 

The 122170 Summit one will work fine.

The small block will live with 50 psi easily at pretty high RPM..I just like oil pressure.

As mentioned a HV one will primarily just get to whatever oil pressure the spring is set at earlier. It will hold more pressure at low and medium speeds. It helps when running a solid cam with either EDM lifters or a solid roller with pressurized oiling to lifter axles. You can push 100+ psi easily out of a stock pump with enough spring..just takes more rpm to get there.

The clearances and leaks within the motor set the oil flow through the engine. Bigger clearances means more oil flow and that's when you "might" need a bigger pump. A HV pump gives the potential for more oil to be moved...but if it's not needed..the bypass opens and the oil is returned within the pump. You don't want to be *on the bypass* all the time....as in a HV pump in a stock motor. You want it to reach max pressure at higher rpm..not just idling down the road.

The Z-28 type spring just allows higher pressure as RPM goes up.

Ck this link for help on pumps. The *select* line is the better stuff..but again...the one you have is probably fine for what you have. I'd still throw a spring in it.

http://www.melling.com/Aftermarket/H...mOilPumps.aspx

BTW- I've never worn a cam gear in my life and I use a lot of oil pressure. Cam gear failure is more likely a meshing problem than an oil pump issue.

JIM

 

You could go with this one:
http://www.summitracing.com/parts/MEL-10552/

10% more volume than standard. CNC-machined body and cover, and hardened steel gears that are up to 25 percent longer, providing additional flow to performance engines with wider bearing clearances. Their drive and idler shafts have been extended into the cover to provide additional support, to eliminate dynamic shaft deflection.

 

I'm going to look this pump up some more.

 

Many years back when building my first-ever smallblock Chevy I installed a Melling hi-volume oil pump. Since it was going in a truck that I would be doing a lot of towing with it seemed like a good idea at the time. Put the motor together, dropped it in the truck, and fired it up. Within a couple minutes it started belching thick clouds of blue smoke out of the pipes from oil being sucked into the exposed PCV valve (I was running aftermarket valve covers with no baffles). I fabricated a baffle for the cover and tried it again...no smoke this time but after a few minutes' running oil was now pouring out of the breather cap on the other valve cover. I was using STD bearings and the crank was at the low limit for journal diameter...my hi-volume pump was pumping the oil up to the top end faster than it could drain back down to the pan. I eventually went back to a good ol' stock pump-problem solved. Everything I've ever read about SBC oiling has said that 15-20 psi at idle is plenty of pressure for a stock motor, and after pulling the pan off of that truck twice I decided that I wasn't gonna give myself any reasons to do it again. I have seen it recommended to put a restrictor kit in the crank-to-cam oil passages to prevent this from happening with a hi-volume pump, and if I was ever gonna run another one for any reason that's what I'd do. My [small block Ford] race car is set up that way, it uses a HV pump, and I've never experienced these sorts of problems with it. Something to think about....

 

I think I'm just going to leave the stock pump on there.

 

after reading this, Smokey Yunick's line of thinking of 10 psi per 1000rpm makes sense

 

You may want to weld the pick up tube in place.

 

The part number for the "Z-28" spring is 3848911, still sold at your Chevy counter. It will keep the pressure up at higher RPM's.

And as stated above, no need for an HV pump on the street.

Good luck!

 

Thanks for that part number. I'm going to look into that ASAP and get this thing going.

 

Put a HP/HV oil pump on a sbc years ago. All I can really remember is that if there was a place it could leak, it did!!! Stick with the stock pump if you have a healthy motor.

 

I sure don't want that happening to my engine. I'm just going to go ahead and look for that Z28 spring and drop it in there.