SBC completely lost oil pressure-HV oil pump to blame?

you can pump 3 1/2 to 3 3/4 quarts of oil up to the top end of a small block chevy and run the gauge to ZERO !! >>>>.

 

I have had a HP/HV Melling pump in my modified 375 HP/327 (Rochester FI) since 1980. I used to routinely run the RPMs to 6500 in races......also have the 5 qt Corvette pan with baffles.....never ran the pressure down.....with over 40K miles on it, the bearings and oil system are still in great shape.

 

Combination of problems that have already been outlined. If a pump is "high volume", EVERY rotation of the pump gears moves more oil than a stock pump (the MV55 is just a big block pump, I've been told). If the pressure isn't high enough to kick the bypass open, then that oil is going up into the engine. Nowhere else it can be going...right? So let's say the pump didn't suck the pan "dry", but did lower the oil level significantly. That in combination with a stock type "swoopy" Chevy pan will uncover the pickup on hard decel.

Mark Donohue ran into this time and again with the Penske Trans-Am Camaro 302s. They helped it with a better pan design which most racers are still using today. They FIXED it by going to a dry sump system.

 

I don't guess it really matters, but a M-55 is a standard sbc oil pump (and if I remember correctly, it comes with a white stripe pressure relief spring in the box to make it a high pressure pump). The M-55A is the high pressure/standard volume pump. The M-55HV is the high volume/high pressure pump and it's the same as a standard sbc pump except that the pump body/rotors are longer than the standard pump.

The bbc pump is a M-77. Some folks run it because the rotors have more vanes and it supposedly delivers a more constant, less pulsing supply of oil.

 

Dead On Ottoman!!!!!

 

Stock volume, stock pressure, good shaft with metal collar,good to go!

 

I do the same unless I'm playing with stock cars. But always go with a major name. I pull them apart and make sure no parts have burrs on them.

Bob

 

Are you running well used stock pushrods and rocker arms?

Its possible for way too much oil to be pumped up the the top end if the holes on the top end of the pushrods are enlarged. It seems to me that the way they wear on the rocker arm it sort of shears off some it this material over time and the holes enlarge.

Oil is only supposed to pump through the squirt hole in the rocker arm when its on a certain point in its travel. running the motor a bit with a valve cover off should show each rocker arm making short squirts. I have seen worn ones pump out the rocker constantly.

 

Hey Scott. I run a 6qt pan with the m55hv, don't wanna even chance it.

 

Are or did you use that crappy bushing between the pump and the rod.I always put the steel aftermarket one in ,Eliminates that crappy oarnge plastic bushing

 

Pushrods and roller rockers are virtually new. Oil pump drive rod is an ARP with a steel collar. Using AC Delco oil filter PF2232
Just picked up a new Melling M55A, took it apart for inspection, and will reassemble with assembly lube after tack welding pickup to the pump piece. Checked pressure relief too. Will install in car and evaluate this week.

 

Do you have the filter bypass blocked? Are you running any additive in the oil? If you said yes to both questions you could have a plugged filter.

 

I have built many engines over the years from Ford , Chev , Olds , Pontiac and Mopar and I have always used a stock Mellings oil pump and never had a problem with them yet ! I have used HV oil pumps before in a stock engine and had problems with them . Unless you have a bigger oil pan you will have nothing but problems ! Stock engines are made to use stock parts ! Now I ONLY use a HV oil pump in a Race engine ONLY !
Change that HV oil pump and the problems will go away !
Just my opinion !

Retro Jim

 

You only need 7-10 psi per 1000 rpms.High volume or pressure cause a lot of stress on the pump drive,power loss,can cause foaming of oil ,and pump all oil to the heads.standard pumps are enough for a natural street strip engine.

 

IS THE PICK UP 3/8 OF AN INCH OFF THE BOTTOM OF THE PAN. iF ITS TOO CLOSE, AT RPM YOU CAN HAVE A PROBLEM.

 

this is funny

for stock clearances you want a stock pump .

for increased clearances , you NEED a high volume pump TO keep the pressure the same.

or tightened clearances , you NEED a high pressure pump to keep the volume the same.

Your reasons for going stock, loose, or tight may vary.

 

i do agree with you on this one 100%. ive always used the hv pump because ive never in 40yrs built a sbc back to stock specs.and ive never sucked a pan dry either.i have run some of cars about a 1/2 qt. more oil.

 

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Fram Filters seem to cause alot of trouble.I've got a new build small block Chevy and when I primed it and started it I never got oil to the rockers.Miss aligned rear cam bearing?

 

circumstantial evidence - My sister had a well worn old chevy pickup 3/4 ton with its original 283. I put a new HV TRW pump in it to improve low oil pressure. Immediately the mechanical oil pressure gage would fluctuate wildly on the highway, similar to porknbeaner,. I vaguely recall it took a few miles on the highway for it to start happening. I do not recall any details about whether min/max oil level changed anything. That's the "what" and I think it's pretty accurate. The "why" behind that behaviour is a wide open.

 

I had smilar problem once, high volume pump not giving me oil. I never figured out if it was sucking the pan dry, cavitating or what - near boiling hot oil won't collect anywhere or pile up or get clogged, it'll run thru a pin hole with enthieusasm.
I believe it was cavitating, i see now that they offer high volume anticavitation pumps.
Anyway, i pulled the highvolume pump out and replaced it with high pressure - i street drove it only to get back and forth to the track on a friday night, 4:56 gears and all - and the oiling became a non-issue.

 

I believe the problem is not sucking the pan dry but oil pump cavitation when using the stock pick up.A votex forms around the pick up head at high demand,similar to the way water swirls around the sink drain slowing the water flow draining out.Cavition with a stock type pick up is talked about in articles by Smokey Yunick and other Chevy engine tuners.
Stock Chevy rocker oiling is not steady but intermittent when the pushrod hole lines up with the hole in the rocker arm cup.I'm just a hillbilly but it seems to me it would be very difficult for several quarts of oil to be pumped through the push rod holes that is open only about 20 percent of the time. And unless the engine has positive type oil seals ,there's got to be a cloud of oil smoke with those quarts of extra oil getting sucked down the guides past the shitty o ring seals.
I might be wrong of course.........

 

I recently built a 502 steel head BBC for my street/strip Camaro. I used a Milodon extra capacity pan and windage tray along with a HV pump. Everything was fine in my 10.30 Camaro but when we put the engine in a buddy's 2300 pound super gas car and ran 8.97 we would lose oil pressure towards the top end. We immediately started thinking we were pumping the pan dry but after extensive research discovered oil was climbing the back of the engine past the pump. Milodon makes a baffle that mounts between the pump and block to prevent such an occurance. Problem solved in my case. Remember to use one if your car accelerates quickly.Just tossing this out for the street/strip racers.