SBC oiling questions - oil pump

So i have some questions regarding my oil pump. Im building a hot 327 chevy. Im looking for about a 6500 - 7000 rpm motor, which brings me to my question. What oil pump should i look for? I currently have a melling M55, but have heard that it might not be good enough.

Any imput or thoughts?

Thanks ,

Marty

 

Hi Marty, I remember using the oil pump originally used in the Z-28 DZ302 engine. It is a factory high volume-high pressure pump. Used it in a 283 and had 70psi when cold and 45psi at running temperature. Good luck!!! Al

 

Dynaflash, I'm pretty sure there's more than one version of the M55, std, High Volume & High pressure. If your running the high volume pump and planning some serious rpms might want to consider a larger capacity oil pan too! I've never heard of any problems with this pump.

 

Get the Z/28 version pump.. Or, you could also use a lo-po big block pump with a sbc pickup tube...

 

The melling M-10550 is what i run in mine. I run it up there to 6500-7000.

 

A lot of this depends on the bearing clearances you intend to run, as well as the oil viscosity. Bearing clearances are essentially a controlled leak; many guys run huge clearances, either because they are slapping it together without bothering to do what's necessary, or because they still believe that engines "need" bigger clearances. Hence, the "big pump-heavy oil" myth. There are a couple of caveats to all this, though (if I may use that word without getting beat up ).

If you are truly going old school and using OE-style rockers, they do require a reasonable amount of oil to survive. There is also some benefit in cooling the valve springs with oil; for example, drag racing engine builders have made a huge effort in the past 25 years or so to keep oil out of the upper end, except a bare minimum. Many of them have now discovered that keeping the springs cool with oil makes them last a lot longer, a nice benefit with $600 spring sets.

Assuming that you are not "that guy", and are planning on reasonable clearances, you can probably get away with a std. pump. You didn't mention what the engine is going to be doing but I'm assuming a hot street engine with some limited drag racing. A std. pump under these conditions and using something like 10W-30 or 5W-30 will make around 40-45 psi max. If you want a bit of extra peace of mind, you can use a different bypass spring in your M55; I believe the "Z28" spring is still available from Chevrolet, or you can use one from Canton, Moroso, etc. The Chevrolet Z28 pump is actually a standard pump with the heavier spring.

You certainly can buy a different oil pump and it won't hurt much, except perhaps your wallet, but I question whether it's necessary, since you already own this one.

My personal preference for Chevrolet wet-sump oil pumps is the Moroso units, because of the internal mods (which can be done with access to a mill).

I would respectfully disagree with Deuces about using a BBC pump. This was done "back in the day" for a couple of quite valid reasons, none of which really are a factor nowadays. The BBC pumps take more power to drive and also require a special length driveshaft. It certainly can be done and there is still one oddball situation where it sometimes is done, but it probably doesn't apply here.

 

No matter what pump you use rember to weld the pick up tube to the pump if youre using the stock one belive me it will fall out at those rpm's.

 

I use the GM performance oil pump part number 93442037
also pick up screen 12550042. Gives me 85 lbs cold and 45-50 lbs hot.Like 76cam says its important to weld the pick up tube to the pump or you could have 0 lbs of oil pressure at 7500 rpm. On the bright side that usually only happens one time

 

One of the reasons that the BBC pump was used was the anti-cavitation grooves milled in the cover. Cavitation in the pump is said to cause spark scatter at the distributor. Im sure Ive seen an aftermarket SBC pump with the grooves milled in the cover, but cant remember where. If you will be welding/brazing the pickup to the body, be sure to take the spring out of the pump before doing so. Heat will weaken the spring which wont help your oil pressure a bit.

 

USe the M55 pump, just change the releif spring to the high pressure one and you'll be ok.

The replacement pink spring can be gotten from Melling, it is the same one they use in the high volume pumps when sold new.

Harry P Hunter

 

A high volume pump will empty your oil pan.
It's shocking how much oil IMMEDIATELY went to the top of the heads and filled the lifter valley (with the above-cam oil holes plugged) while we were pre-lubing the engine.
Use a low-volume, high pressure pump.
-Brad

 

When I built my motor I used a standard pump as I had heard a hi volume was not necessary.

I noticed at over 5k rpm or so the oil pressure gauge would not hold still. I never found out the reason but switched to the z28(hi pressure) pump and its been fine for the last 10 years or so. This was on a fresh rebuild with tight clearances.

any idea what could have cause the erratic pressure with the standard Melling pump?

 

I'd be very careful before running an oil pump with the anti-cavitation grooves in the pump body and end cover in a street engine. In Melling pumps they usually have a "C" suffix. They do help with high RPM spark scatter, but also reduce hot idle pressure to 5-10 PSI at normal street engine idle speed. They work in race engines that idle at 2500 fine. I got this from a Melling engineer.

 

Low idle oil pressure is not a problem. Anything over 25 is OK. Too much volume like stated above does require more HP to turn it and that will be exponential as RPMs rise. I find that the most reliable mods are good baffling, drain back control, and reducing cavitation to avoid tha scatter also mentioned above. While it is important, the oiling system in Chevy engines were among the best ever engineered and over-thinking on anything but all out race applications can lead to a domino effect of other changes not considered. Also for what it's worth, I'll confirm the oiled valve spring theory. I had over 350 passes on a BBC roller cammed combination with the same springs. They lost 5# on the seat pressure and less that 20# open. I kept the mass in the valvetrain down by using 3/8 moly pushrods. Since they fill with oil they were much lighter than the common 7/16 and were also plenty strong. Lift was .714 on that one, oil was only limited marginally. That one went through at 7800 RPMs. It worked. I used a stock BBC oil pump with an OEM 6qt pan and a screen windage tray.

 

Smokey Yunick used a stock big block pump and port matched the SB mounting orifice to the BB pump. I've done it, didn't notice much difference but it worked and never had problems. Oh, and an oil pressure rule of thumb according to Smokey, 10psi per 1000RPM

 

I like to use the big block (stock volume, stock pressure ) pump #m77 for my circle track engines.. Less spark scatter and a lot beefier where it mounts to the main cap ( a big plus on the dirt track ).. Uses stock o/p driveshaft...
For street / strip use I use the melling # m65...Z28 pump.. specs are 20% more psi (72 vs. 60 ) and 20% more volume...than the stock small block # m55..
The m55A (high pressure) or m55hv ( high volume ) both bring on other problems , such as cavitation ( hp) and emptying the pan (hv) that the Z28 (M65) do not....
BTW, the specs for the m65 and m77 (pressure and volume ) are very similar ..
Lessons learned from 40 + years of building performance engines..
Dave

 

ok fellas,

So to mount a big block oil pump, what all needs to be changed?

 

I didn't change anything, just matched the opening on the main journal where the oil pump bolts up and used the pickup tube for my pan.

 

Smokey always told me that it only takes just a little bit of pressure to float the bearings, like say 5 to 8 PSI....but that was for getting max outta the motor. I'd say 'Holy S---!!!! No oil pressure!', he'd look and laugh....oh, thats plenty for this thing, puffing on the corncob pipe....

 

You might think about what happens to the oil inside the pump. Look at the path of the bypassed oil, and you will see that it is put back into the intake side only to be passed thru the pump again and again (old news, yes). If you keep this up very long and it starts to foam (air in oil), not a good lube agent.
Take a look at Smokey's book and you will find his solution. By directing the bypassed oil back to the pan you do two things.
1. Pure oil, no foaming. Air is not a good lubricant.
2. cooler oil entering the engine, continuous compression generates heat.
Reduced oil temp helps bearing life.

Some coatings (thermal) are also a help in pumps.

 

A slightly longer mounting bolt, and the correct (3/4" ) pickup tube..
Be careful when selecting the o/p mounting bolt...Too short will tear out the threads in the cap and too long will bottom out and lock up the rear main bearing.
Dave

 

A arp stud is what should be used. The pump is not the only thing here. Proper oil pan windage tray or screen too. Moroso stuff is good . Good luck.

 

Why not a high volume pump like the M55HV? Ok, accept you need a higher capacity pan at above normal street driving RPMs.
What are the downsides for using a high volume pump? Heard somebody say bearing erosion during a conversation at work, bs? What else? HP usage, know it will.
I build a 358 sbc with a M55HV. It splattered because of rod bolt stretch by REUSING STOCK ROD BOLTS. I F'D BECAUSE I REMEMBER FEELING THE TORQUE WRENCH GIVE while clicking at correct torque, twice.
My avatar is a 331 made of assorted parts and good machine work. Takes 2 gallons for an oil change, so sustained RPMs and etc don't matter to me, I'm on reality street. I'm figuring my large oil pan is a cheap ass oil cooler too, like in hydraulic systems using the reservoir for some of the cooling capacity. My line of thinking is I can use Rotella 10W30 oil with a high volume pump and have plenty of oil pressure based on previous experience, and have years sustained bearing life because of oil pressure. I built my car to satisfy me, and hope to drive it 250k miles on one engine. Anybody get bored with not needing to pull an engine for many years? Damn, hope I'm on the right track.
Paging Enginepro 5X, Big Chief, etc with thoughts!!!!

 

Ok, here you go....
High volume pump will solve SOME problems due to excessive clearance.
Problems created , among others, are excessive windage, emptying the pan, and smoking/oil burning due to build up of oil in the valve covers..
High pressure pump WILL cause cavitation and cost horsepower for no real benefit...
As stated earlier, 10 psi per 1000 rpm is more than adequate.
With my personal recomendations as stated m65 (z28) or m77 (stock big block ) both speced at 72 -75 psi...... 7200 rpm works for me...We ocasionally spin the race engines to 7600...No Problem.
I spent a lot of time and money chasing the hp/hv/big block/small block thing..Bottom line is, GM spent WAY more time and money than me. If the z28 pump worked for a high reving road race motor, It should work for everything we hotrodders do !
All this info goes right out the window if you run an remote oil filter or cooler,or have your rod, main,or side clearance out of spec !
JMO
Dave

 

I did just like (POST # 10) on my 327 build,

and turn it hard most every time I drive it ,

6500 to 7000 in my 66 El Camino just so you will know what car its in..

Never had a problem and oil pressure is never below 25 pounds .....

Good luck with it......

 

I read a bunch of stuff from several years ago about Melling M55 (and similar) pumps breaking because of an updated casting that was weaker than the old design. Almost everything I read said not to use any M55 in an engine that will see over 5000rpm. It was recommended that for performance engines to use the M-select 5-digit pumps (like the 10553) that use the older casting design. Is this still a problem?

 

To Homespun91--------------thank you brother, someone who actually understands the myth and the B.S. and most importantly, THE BLATANT mis-use of H.V. oil pumps. Heavens to Betsy, I could go on for hours, but here is one EXTREMELY important fact and question to ask yourself------------what have I done , as the engine builder or assembler, to get all that " high volume " of oil BACK to the pan so it can go through said H.V. pump and circulate back through the engine????????????? Any real engine builder who has ever installed a 2,3, even 5 stage external pump knows damn well the work involved to get that oil scavenged and back to the pan or oil tank for it's next lap through the engine. Hours of grinding and relieving, hours of plumbing external lines/fittings, etc, etc. Here some other myth, you ask then why does most or all of new crate engines come with H.V. pumps? Because, its cheap insurance, these engines are no better, and possibly worse { clearance wise} than most engines from the factory. They are not " blueprinted " and " clearanced ", so they stuff a H.V. pump to keep the engine from coming back for warranty and destroying thier reputation. Keep in mind APPROXIMATELY 10 psi of oil for every 1000 RPM's after the engine is at temperature is a good rule of thumb. A good stock volume pump, good pick up- set to the correct clearance from the bottom of the pan { very important }, and adjust your pressure to your needs. PLEASE this is NOT the end all of discussions on the topic, it is a starting point of a naturally aspirated mild performance to everyday build with bearing clearences remotely within spec. Still insist on a H.V. pump, please don't forget use a hardened shaft. BDM

 

One night in the shop the curiosity got the best of us. We took a fully assembled small block and started dumping oil in it 1 quart at a time. When we got 3 quarts of oil in it we started running the oil pump primer. The gauge went right up to 60#. Stayed there for about 10 seconds then went to ZERO. So we kept the primer going and started to add more oil slowly. It took 3/4 of a quart to keep up the # on the gauge. Now we went 1 step further. While the primer was running with 4 QUARTS of oil in the engine we start to rotate the crank to open and circulate more oil passages. Once again we could see the gauge start to bobble. So with 4 QUARTS of oil in a small block chevy you can cavitate the pump. Keep in mind the oil was cold and we had done a small bit of massaging to the drain backs but this scared the shit outta us when we made the test !!! Test was made back in the 70s with the standard issue Melling 55HV oil pump >>>>.

 

How many of you guys read the book on "How to hot rod a small block chevy??? Great book!! I read an article on how to "blueprint" the oil pump. It sez that once you buy one to disassemble it and check for gear clearance... With the cover off, use a straight edge and a .002" feeler gage. If there is too much clearance between the gear ends and cover mounting surface, you need to sand the housing down using the figure 8 motion with a sheet 400 grit sandpaper on a flat surface like a grannet(sp) table..... If there's not enough clearance, then sand the gear ends in the same figure 8 motion to come up .002" clearance..

 

I run a std volume / std pressure Melling on my F1 Procharged 377 SBC. 20# at idle and 60+ through the traps at 8,000. Of course I'm using 50wt oil. Never had a pressure drop issue. Rock steady.

I never did understand why people run HV pumps. I mean, how much oil do you want sitting on your top end?