340 oil pump

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bobscuda67

bobscuda67

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Hey guys. I'm building a 340 based 373 ci engine and need some direction on which oil pump to use. It will be street driven except with a few dragstrip passes a year. The car is a 67 barracuda with a 904 shifting at about 5700 rpm. Should I use a stock pump which runs about 50 psi, or high volume. How about a high pressure relief spring on a stock pump? Thanks, Bob
 
Bob this is something I've read alot on because there's alot written out there by guys that can prove either is the right one to use. I have still yet to find the correct answer. Some say you can't use a HV pump with a stock oil pan or you will suck it dry. Others say it's no problem. In fact I have a buddy with a 340 Cuda that has a HV pump and a stock pan and he races some and has no problem and his car runs high 12's and he put it together 6 yrs. ago. Some other guys say use a high pressure spring and that's all that's needed. Then others say that's not a good thing either cause higher pressure means higher oil temps. which is true so go figure. IMHO if you run loose clearances run a HV pump. If you run stock clearances run a stock pump. A deep oil pan is never a bad idea either. Also consider deburring the block when rebuilding it so oil drains back faster. And if you run a windage tray I've heard to bend the drain flaps out straight so they drain quicker.

Good luck with your project.
 
I used to use HV pumps and stock pans all the time. I never ran one dry, even with high steady rpms, and darg racing them. But..time and experience...An old engine with some miles and iffy clearances, I'll use an HV straight away. My truck's 400 with 80K miles has one with a stock pan. As does my '70 with a factory original milage 70 shortblock in it. (trap rpms is 6400, runs 113 mph) Any rebuild I do now has proper clearances, and doesnt need or warrant a HV pump. It sucks a lot of power just to pump excessive amounts around, and trying to compress it generates heat. You can feel the drag when pre-oiling a new engine. So I use a std pump from Melling, with the high pressure releif spring. You need 10psi for each 1000 rpm. So if you're shifting at 6300, you need minimum 63psi to stay safe. The HP ones usually run at 70psi, but dont sap as much power or heat the oil up as much. That's how I do it..But like you said..everyone has an idea...
 
Good info posted above.....I run a Melling HV pump in my stock pan with 6 qts of oil and I shift at 6000 and have never sucked the pan dry.......for you motor being a stroker I'd run the HV pump just to be safe. Are you running a deep pan or stock pan?
 
I agree with everything said. It also matters how much oil is in the pan to start with. Reason is some have stuck the oil pan dry at high rpm's with a HY pump but maybe the motor was a quart low to start with. Not everybody checks the oil each time they fill the gas tank up and if the motor does not burn oil or leak you should not have too but if it starts burning oil and you forget to keep the oil up a HV pump is more likely to run out of oil to pump. Cold oil does not drain back as fast but again not everybody waits till the motor is fully warm up before they get on it. Agree that bigger oil pan is the best idea but its too bad a 5 quart small block pan is hard too find. I see only stock 4 quarts or a deep 8 quart which you loose ground space.
 
I got a MP pan and no it was 4 quarts but that was 5 years ago maybe thats changed too now. IDK If anything my pan is a half of quart less than the Mildon pan I had that got wreck when the rod threw
 
I swear my center sump MP kit was a 5qt pan. I run 6 Qt in it with the filter and it's barely over the full mark on the dip stick.

dodge freak said:
Sometimes too the pump pickup is not low enough and the motor could have 1/2-1 quart of oil left but the pickup for the pump can not get it.
Click to expand...

Good point.......I know a lot of guys that just bolt the pan on and go. I always index the sump and the pick-up. It's time consuming but worth the effort.
 
If you are generating 50 psi with the stock pump then stick with the stock pump. A pump just moves fluid, what creates pressure is a restriction in flow. If you have a "tight" motor your pressure will go up until you reach the relief valve setting, in this case 50psi. If you have a "loose" motor you may not be able to get to your relief setting because the oil is bleeding off past the clearances almost as fast as you can pump the oil. In other words the volume of the bleeding off matches the volume of the pump. In this case you need a higher volume pump to overcome the clearances so now your pressure goes up.
So if you are running a HV pump with a "tight" motor you will never run your pan dry because all you are doing is putting the oil back into your pan thru the pessure relief valve in the pump. So this is just wasted motion. What is the advantage of running something bigger than you need and wasting the overage buy putting right back were you got it? Running a HV pump also puts more load on your pump drive gear. More load = less horsepower. I run a stock pump in my 340 drag car that runs low 11's and my oil pressure is just fine, it is 70 psi at 7000 and 20 at idle hot. It's just a matter of matching clearances to pump volume. HV pump came around in the 60's and 70's with the advent of very loose clearance race motors. the only way for these motors to build pressure was to run a big pump. Now we have gone the way of tight clearances and smaller pumps and thinner oil. Ever notice how some modern motors use 5w-20 oil? it's because of tighter clearances.
Just to clarify one thing you can't compress a fluid.
I also run my drag cars one quart low so I don't whip up the oil from the windage of the crank spinning. Introducing air into your oil or any hydraulic system is very bad.
 
I have a 360 that I rev to 6,500+ and can run mid 11's with a stock volume and stock pressure pump. Almost 2 seasons on it and no problems. If the engine in clean, has proper clearances, good oil, etc., you should have no problems. I use Amsoil synthetics.

I have seen tolerences on stock pumps vary. The case that comes to mind was one that had a just noticable amount of extra verticle clearance than another one. I used the tighter one.

Good advice already posted.
 
Thanks for all the info guys. My plan was to use a stock pump and 4 quart pan. All the clearances on the mains are .0015 and the rods are all .0015 except two are .0017. I checked them with plastigauge and I know its not that accurate. Rod side clearances vary from a low of .014 to a high of .017. It all seams to be withen factory tolerances. I thank you for input, I just needed some reasurance before I screwed it together. Bob
 
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