Stock is fine, Fits manufacturers guide lines. Hi volume better, Manufacturers guidelines plus more flow. Hi presure requirers clearances, I have washed my bearings thru the center jurnal with hi presure.
If you are talking Chevy here, just O-ring the dist body and you'll have all the flow and pressure you could ever need with a stock pump.
High pressure robs HP & can cause other problems as mentioned earlier. HV pumps push more oil through for better cooling, but if the drain back is poor you can pump some sumps dry with extended RPM running. New engines should last 100K, so there must not be anything really wrong with OEM pumps.
Chevrolet recommends 10 lbs. oil pressure/1000 rpms. So if you're not turning six or seven thousand rpms, a stock pressure pump will be fine. And I never use a high volume pump unless my customers want to see high oil pressure numbers at idle. If you think about it, the more rpms you turn, the more oil flow there is. Just about any pump should move enough oil to keep an engine lubed at higher rpms if everything is right in the engine. Larry T BTW Chevrolet used standard volume/high pressure pumps in their Z-28 302's.
As George says above...all true ! After 43 + years of messing with sb chevys, my choice for a stock or mild performance engine is the Z28 pump (m65). 20% more volume, 20% more pressure. Dave
Low performance big block oil pumps work on a small block also... It uses the standard sbc oil pickup tube...
As has been said it all depends on what you plan on doing with the motor, and clearances. Too much flow and stock pans, with poor drain back can cause problems. Consult with your local engine or machine shop and they should be able to spec out your assembly and let you know what you ned to be running. Or PM me and I'll put you in touch with my machine shop here at JR's.
The dist body goes thru the main oil gallery and is a pretty sloppy fit. If you look at high end dist, they have two orings thet can help seal off the gallery to prevent the oil from leaking back to the pan and into the valley. The instructions say that the block needs to be modified by cutting champhers so the orings don't get torn, but I have never done this and have been able to carefully get the dist body with orings installed thru and never cut an oring. You can see on a used dist where the upper and lower portions of the gallery is and cut an oring groove in the dist housing in those two areas to seal off the oil passage. You can do this on any Chevy dist in a lathe. MSD sells the orings for their dist, or you can use two that fit from an assortment. Frank
Dave, I guess we'll agree to disagree. I always operated under the impression that the stock Z-28 pump (3848907) was uses a 1.20 length rotor and the high performance "white" relief spring (3848911), while the high volume pump uses 1.50 length rotor. Larry T
Sorry Deuces, big block pumps use a 3/4" pickup.. small block pumps 5/8" That said....I use std big block pumps ( M77) on my race engines.. All the info I have posted here is based on 40 +years of trial and error. + lots of broken parts along the way!! Dave
There are big block pumps that have the 5/8 id tube inlet!!! Check it out!! I built 2 small blocks using those oil pumps...
Sorry but all the late model SBC's after 87 or so changed to 3/4 pickups. I use the 3/4 pickup pump M 155 HV for HP motors.
Just to keep the records straight, the Z-28 used a "hi-pressure" pump with no add'l volume!! This would be the Melling part number M-55A. This is basically a stock SBC pump but utilizes the "purple" (M98015) spring that was "standard" in the SB "hi-volume" pumps! We install these springs in (almost) ALL the SB's that leave here today. The only real time you would need a HV pump in anything is if there are aluminum conn rods in the program. These usually see in the area of .004" bearing clearance. Same story for the Melling M-77 BB oil pumps. We install the "purple" spring (M77020) into these pumps making them "hi-pressure" with no increase in volume. The M-77HV pumps come with this "hi-pressure" spring from the mfr. All the "hi-volume" pumps are harder on the cam/distributor gears for wear! The lower distributor rail should be modified, with a small slot, to get direct oil pressure to the "point-of-contact" (mesh-point) on these gears! Helps cool the gears and eliminate excessive wear (see below)! Thanks, Gary in N.Y. P.S. Most "streeters" need only a stock oil pump, the "hi-pressure" option is needed when the horsepower numbers are pushed up. Below here is a shot of the distributor mod. Can be done by hand with small 3-cornered file. Also a shot of the BB "hi-pressure" pump springs.
The big block pumps I ordered for those small blocks were for a 396/325hp motor.. Hope that helps! I believe there's an article on that subject in "How to hotrod a small block chevy.... Great freakin' book!!
I use the high volume/ high pressure pump in all the small blocks I build for my trucks that I transport a bunch of the toys on this site, my pressure is 60lbs at cruising speed 2000 rpms & 40lbs @ idle. I have well over 2 million miles onthis setup & have never had any oiling or bearing issues all but one of these motors lasted over 250,000 miles. they are balances 30 over 350s with performer cam, manifold & chain & gear packages. I change these motors before they break & upon disassembly I have found no issues what so ever.
I'm using the Comp Cams solid flat tappets that have the .012" hole EDM'd into the cam face of each lifter for better cam lobe lube. Tech @ CC advised using HV pump because of extra 16 oil bleed holes. So I used Melling HV pump. Must be the correct choice as the oil pressure @ idle is around 40 and peaks about 60 with Joe Gibbs break in oil, which is around 30 wt.
Ok , so my mind is failing..like the rest of my body ! Here is my awshit moment... The Z 28 pump part number stuck in my brain is the old TRW #50065...IE; 302 z28 and 350 hp/special hp engines.. The melling equivlent is #M55A, not m65 (that is a small block ford #) Yup, Im getting old.! So to back up my info further...The melling pump m55hv is listed as having 25% more volume than stock.. No info listed as to what pressure or volume the m55a produces. It is still my contention that the M55a or the 50065 produce 20% more pressure AND 20% volume than a m55 (std ) pump. There are other pumps listed (newer style ) with 3/4" pickup tubes. Also listed are hp, hv, and hp/hv combo pumps.. I also cannot find any big block pump listed that uses a 5/8" pickup.. So back to my personal specs...small block in any form except full race> Z28 pump. Race engine > m77 = std big block pump and pickup . Dave
Hi Dave, the Melling M-55A and the TRW 50065 are identical pumps. Both are listed as "Hi-Pressure" only, no add'l volume!! It's written this way in the TRW catalogs! The Melling M-55 and the TRW 50029 are also the same "stock" SB pumps! The ONLY difference between these pumps and the "Hi-Pressure" ones is the M98015 "Purple" spring to raise the pressure to 60#/65#. Other than this spring, the pumps are "standard" volume deals! If/when a "Hi-Volume" pump is thrown into the equation, you MUST have at least an add'l quart of oil added to the system. This usually requires an aftermarket style pan. Some of the early Vettes with a 5-quart sump can get by with the HV pump. It's really not needed as I stated in most "drivers". For many decades now we would purchase the Melling M-55 pumps (std volume) and replace the spring shipped in the pump with the M98015 (purple) one and this made the M-55 into the M-55A. It was simple. The Melling M-55HV and the TRW 50135/50068 (screen included in this part number) are "Hi-Volume" deals and normally speaking have longer gears in the program! The "purple" spring (M-98015) is standard in the Melling HV pumps! Not sure about TRW's spring colors! Thanks, Gary in N.Y. P.S. If you have any oil pump questions you can drop an e-mail to George Richmond out at Melling! They made many of the original G.M. factory pumps! His e-mail address is: [email protected]. He is a friend, I speak with him often, just yesterday about the Flathead M-19 pumps!
I would not use a High Pressure pump. I do however replace all stock pumps with High Volume pumps, even if I do not use a dry sump system in racing. Dry sump is different all together. Bottom line is, if your replacing your oil pump, use a High Volume pump. Melling or TRW are my choices Your oil Guage cannot tell the difference between volume and pressure, so it will always read High pressure in either instance. High pressure pumps have been linked to spun bearings. I dont know why they still make them to be honest.
Gosfast, maybe my belief is based on some basic engineering formula buried deep in my OLD brain... Something about increasing pressure bringing about an increase in volume ?? The last time I talked to a melling tech was 1975. That is where I got my info..And that is when I stopped having oiling problems with my sbc engines.. Old school, no doubt..But it works for me ! Dave
High volume pumps will create high(er) pressure. For any given set of circumstances, as you force more fluid through a fixed orifice the pressure goes up. Basic physics. Your gauge reading indicates this change. If you need to check the theory, consider the difference when you put a small 'blaster' nozzle on your water hose. .
The only thing the higher volume would do would be to open the bypass sooner than a standard volume pump would. Once the bypass is opened, you shouldn't build anymore pressure no matter what the volume is. However, the bypass would cut down on the volume too. I don't see where there would be any difference in pressure in a high pressure pump and a standard pressure pump until the you have enough volume to open the bypass spring, which is usually above idle. Larry T
All correct, there is definitely a correlation between pressure and volume. The variables are the clearances and other oil "leaks" in the engine. At idle, both stock and high pressure pumps will be on par, as neither will likely generate enough oil pressure to cause the pressure relief to open. In the same engine, a high volume pump will show a higher pressure at idle, simply because it is moving more oil through the same bearings and "leaks", or as stated above, attempting to push more liquid through the same orifice will show an increase in pressure. A worn out engine that has low oil pressure may benefit from a high volume pump, because it will supply additional oil to those worn bearings, but it is a short term band-aid. Engines with loose clearances, you need high volume. High RPM, you need extra pressure and volume, which go hand-in-hand. Editorial: Think about the centrifugal forces that the oil has to deal with in a crankshaft. At high RPM's, the pump has to push oil through main bearings into a journal that is resisting the flow of that oil, due to centrifugal force. The oil has to be pushed into the oiling hole at the outer diameter of the main journal at least as far as the centerline of the crankshaft. At this point the centrifugal force becomes your friend, and creates it's own pressure by flinging the oil through the oiling passages towards the rod journals.
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