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Melling M155HV Oil pump?

39K views 34 replies 10 participants last post by  cool rockin daddy 
#1 ·
Hey all, got some goodies today. I ordered my oil pump along with a pickup for a sbc 383, and a Moroso 7 quart stroker clearanced oil pan (8.25 inches deep). My question is, although the box the pump came in says it's an M155HV on the label, the casting number on the actual pump says it's an M55HV. Melling has an M55HV pump, and it's slightly different, also being high volume though (different model). What is also weird is that on the pumps bottom half, the bolts that hold both halves together came with a metal 'tag' on one of them that has M155HV etched into it..totally confused by this. Has anyone had any experience with these pumps?

I'm also a bit worried on the clearance it will make on the bottom of the pump, being that with the pickup attached to the oil pump it's only 5.25 inches long, giving it about 3 inches of play...that just doesn't seem right. I could be wrong, and it could be the fact that it's the wrong pickup anyways. (.625 inch inlet, oil pump is 7.5, didn't bother to say that on the summit site..). If i've got all the wrong parts, what do you think would work with this pan i've gotten? What would you recommend? I can provide pictures if it helps you understand my confusion.
 
#2 ·
First see if moroso makes a 3/4 inch inlet pickup, for the pan you got.

The m55hv has a smaller inlet.



mrdreex said:
Hey all, got some goodies today. I ordered my oil pump along with a pickup for a sbc 383, and a Moroso 7 quart stroker clearanced oil pan (8.25 inches deep). My question is, although the box the pump came in says it's an M155HV on the label, the casting number on the actual pump says it's an M55HV. Melling has an M55HV pump, and it's slightly different, also being high volume though (different model). What is also weird is that on the pumps bottom half, the bolts that hold both halves together came with a metal 'tag' on one of them that has M155HV etched into it..totally confused by this. Has anyone had any experience with these pumps?

I'm also a bit worried on the clearance it will make on the bottom of the pump, being that with the pickup attached to the oil pump it's only 5.25 inches long, giving it about 3 inches of play...that just doesn't seem right. I could be wrong, and it could be the fact that it's the wrong pickup anyways. (.625 inch inlet, oil pump is 7.5, didn't bother to say that on the summit site..). If i've got all the wrong parts, what do you think would work with this pan i've gotten? What would you recommend? I can provide pictures if it helps you understand my confusion.
 
#3 ·
dgcantrellsr said:
First see if moroso makes a 3/4 inch inlet pickup, for the pan you got.

The m55hv has a smaller inlet.
the inlet on the pump I have now is .75 in., and the inlet on the pickup that I received is .625 in. I know it's the wrong pickup, and i'm going to be sending it back. Moroso does make a 3/4 in. inlet:
http://store.summitracing.com/partd...301038+4294778905+4294778140+115&autoview=sku

I just wasn't aware of the inlet sizes when I was ordering, because they weren't presented =/ I called and made sure it would fit (summit) and the guy that answered was more than willing to say it would work..go figure. I won't dog on them all, just some of them are more interested in selling you stuff than actually helping you out.
 
#4 · (Edited)
Melling oil pump ID

I know this is probably old news but...
The Melling casting numbers on the pumps is not necessarily the part number. Melling somtimes uses their older casting mold designation when casting new oil pumps. .If the description says it is for a "SB Chevy" and nothing else, it is generally understood to have a 5/8" inlet. The numerical prefix "1" indicates the SB Chevy pump has a 3/4" inlet. Just because it is a "high volume" pump does not mean it will have a 3/4" inlet and just because it has a 3/4" inlet does not mean it is a high volume oil pump. The "high volume" oil pumps have spur gears that are longer than standard oil pumps and they have a 0.587" longer pump housing. The pumps that are "high pressure" are equipped with a stronger by-pass spring.
Caution: High volume and high pressure pumps in a engine with standard bearing clearances usually accelerate distributor and cam gear wear. Always machine, grind or file 0.030" wide x .030" deep oil groove from the bottom oil passage on the exterior of the distributor shaft housing to the distributor gear for improved oiling. Always replace the nylon sleeve type drive shaft with a ARP,Melling, Moroso, etc., aftermarket drives shaft that has a steel sleeve, whatever pump you choose.

Melling M55
Std. pump, std. pressure, 5/8" inlet.

Melling M55HV
High volume, high pressure, 5/8" inlet.

Melling M155
Std. pump, std. pressure, 3/4" inlet.

Melling M155HV
High volume, std. pressure, 3/4" inlet

You can increase the oil "pressure" by replacing the standard pressure by-pass spring with the "high pressure" relief spring that comes in the box with the pump or purchase one separately and replace the standard oil pressure by-pass spring. Doing that will allow the pump keep your engine oil under pressure at a higher RPM before it by-passes. (when I was a kid of 15, and could not afford a tachometer, I used the oil pressure guage to tell me when to shift :rolleyes: ). High pressure pumps require more frequent oil changes because dirty oil and a high pressure pump is just like sandblasting the bearings when spinning the engine at high RPM. That is called "washing out" the bearings, not wiping out. .

The M155HV pump has longer spur gears for "high volume" which makes the housing 0.587" longer. Therefore you must use a deeper pan and an aftermarket longer pick-up screen assembly. You cannot use a Chevy high volume oil pump in a stock oil pan. That is because the stock oil pump pick-up assembly is as short as it can get due to the location of the oil pump. That is why a high volume oil pump CANNOT suck a stock oil pump dry! However, that is not the case for all engines. For example, Pontiac engines with their "high volume" oil pump CAN suck a stock depth oil pump dry because the Pontiac high volume and standard volume oil pump is the same length which permits the HV pump to be used in a stock Pontiac oil pan. Pontiac so-called "high volume" oil pumps merely use a stronger by-pass spring and a 3/4" inlet, and they are not true HV pumps. Usually high volume and high pressure oil pumps should only be used if yoiur engine has a remote oil filter and oil cooler or the bearing clearnces are loose (.003" or more) as is found in some race engines. It has been proven on the dyno that a high volume oil pump requires 3 to 7 HP to turn it (depending on the RPM) compared to a standard oil pump.

I went through this with my 1991 S10 Blazer 4X4 with a 4.3L engine. The pick-up screen/pump combinations are nearly endless when trying to achieve 0.375" to .500" oil pan to pick up screen clearance. The S10 Blazer 4X4 has a oil pan sump that is 9.250" deep and after several trial fits with a few different oil pump pick-up assemblies, I will use a M155HV pump with standard pressure by-pass spring and a Milodon 18201 extreme duty pick-up screen assembly that is designed for a 8.250" deep oil pan.
The math: (8.250" pick up + 0.587" longer oil pump) = 8.837" pick up depth. Then: 9.250" pan depth - 8.837 pick-up depth = 0.413" pan clearnce......dead nuts on. More than 0.500" clearance between the pick up screen and the oil pan will cause a vortex to form and the resulting cavitation will cause air to be drawn into the oil pump with a loss of oil pressure.

The Moroso and Milodon oil pump pick ups press-in the inlet hole and also have a strut that bolts to the bottom of the oil pump. Using Milodon or Moroso bolt on pick-ups is simple and is more secure than brazing the pick-up tube to the oil pump housing. Brazing is a weak weld to cast iron, especailly not done correctly. .Do not trust the the Melling Select bolt on oil pump pick up screen assemblies because the tube is merely bronze soldered into the inlet bolt plate and does not enter the pump at all. I feel like vibration can break it loose with disasterous results.

Be advised:
1.) Securing the oil pump pick-up in some manner is absolutely necessary if you have a deep pan with a extended oil pump pick-up screen assembly.
2.) You may want to use the more expensive Melling Select oil pumps because the regular production Melling oil pumps, made after 1990 are lighter and have weaker castings, thanks to the bean counters at GM. The new design of the standard production Melling oil pumps have been known to break off the main cap especially when using solid motor mounts. Melling gives that disclaimer with a note in the box. I found my pre-1990 new old stock Melling M155HV oil pump on e-bay, still in the original Melling unopened box.
 
#6 ·
Adjustablke?

Adjustable pick-up screen assembly? You got to be joking. The oil pump pick up tube must be installed in the oil pump in a manner that will make the pick-up screen parallel and within 3/8" to 1/2" from the botom of the oil pan. Therefore the pick up tube must enter the pump only one way. When you press or drive the tube into the pump, you must first mark the pump housing and the pick up tube in some manner so you can install the tube with the pick up screen oriented in a position that is parallel to the botom of the oil pan. With a stock oil pump, pick-up and oil pan, you do not have to be concerned about about the clearance from the bottom of the oil pan to the pick-up screen because the pump, screen and pan are designed in such a manner to make them fit correctly. The problem become apparent when you try to install a aftermarket high volume oil pump in a stock oil pan.

Since a HV small block Chevy oil pump is .587" longer than a stock volume pump, the pick up screen will not fit within the oil pan. In that case, an aftermarket deeper oil pan must be used with a aftermarket pick up screen assembly. . That is why Chevrolet does not sell a high volume oil pump.

High volume oil pumps and deeper oil pans are only available from aftermarket suppliers.

Do not confuse an aftermarket "high volume" oil pump for a SB Chevrolet with a Chevrolet high pressure oil pump. The latter is avaliable from any Chevrolet dealer and will fit any stock Chevrolet oil pan. Or you can buy the just the by-pass spring from Chevrolet dealer and replace the one in your stock low pressure oil pump. The Chevrolet high pressure oil pump is merely a standard oil pump with a high pressure by-pass spring.
 
#9 ·
Well, cobalt, I couldn't agree more with you on that. So many hotshots that are just plain ignorant. Perhaps this guy is Ap72's brother. I posted a link so he can read that the pickup for the melling 55 highvolume pump does indeed fit a stock pan. How long before he posts the obligatory flame where he tells us old farts to go pound sand, blah, blah like they all do when proven wrong?

http://www.summitracing.com/parts/MEL-55-S1/
 
#10 ·
Said I was done, but thought I might just add one more thing.

As to:
That is why Chevrolet does not sell a high volume oil pump.
You might want to check THIS out.

I don't have a standard and a high volume pump handy to compare, but I recall someone recently saying the height difference in the spur gears is compensated for in the casting, making the pump pick up locations virtually the same between the two types of pumps.
 
#11 ·
The pickup tube location is different between the standard and HV pumps. But, for a street car, it doesnt matter much. The after market racing pans require different pickups for the various pump designs. Preferably, I use the new one piece pump-pickup units whenever possible as there is no chance of the pickup falling off.
 
#12 ·
Where is a reference to a high volume pump?

The Summit link shows a stock replacement SB Chevrolet 5/8" oil pump pick-up assembly. Don't you recognize one when you see it? Or, maybe you put in the wrong link by mistake. Nowhere in the description does it mention a high volume oil pump. Search again and show me a pick up assembly for a HIGH VOLUME volume oil pump pick-up that can be used with a stock oil pan.

If some street squirrels claims they have a aftermarket high volume oil pump and are using a stock Chevrolet oil pan, they are blowing smoke or they have been told they have a high volume pump by the crook who built their engine.
 
#14 ·
Did a side-by-side comparison (not perfect-perfect, but colse enough).
Definitely longer gears/housing (as I recalled), but there is some difference
directly below the pump shaft. Possibly to compensate for the longer gears/housing?
But I remember there were physical-differences in height overall, but that slight
difference can be made-up by pickup tube adjustment.

P.S. Most of my engines ran stock pans, with HV oil pumps. No clearance problems.

 
#16 ·
Cobalts link took me right to a GM Performance High-Volume pump .

M-Fink also has the difference in length wrong, the HV gears are only .300" longer, not .587".

I've put plenty of HV pumps in stock GM SBC pans with no problems setting the stock pick-up assembly to within 3/8" of the pan floor, the difference is not that large that it cannot be accomodated with slight reorienting of the pick-up when it is installed into the pump.
 
#17 · (Edited)
Tried it.

You are correct in that the oil pump "GEARS" are 0.300" longer in the HV pump than those found in the std. pump, I cannot disagree. Apparently, the fit depends on which oil pan you are trying to fit the M155HV pump into using a stock 3/4" pick up. You may be able to beat, bend and twist the stock Chevrolet 3/4" pick-up attached to a Melling M155HV pump and fit it with a minimum of 3/8" clearance from the bottom of a oil pan. I prefer not to try that procedure on mine. A long pick up tube and screen such as the one found on my '91 S10 Blazer 4X4 must have additional reinforcement or it will come adrift in the oil pan. TIG, brazing or nickle welding it to the pump housing is NOT the answer. Bolting it to the bottom of the pump is the answer.

I did not meaure the length gears because I did not disassemble the new Melling M155HV pump. However, when the engine was on the engine stand, I bolted the M155HV pump to the main cap and duct taped the stock 3/4" pick up to the pump housing with the screen parallel with the pan mounting rails on the block. I then measured the depth at which the pump screen would be and it meaured 9.00" from the pan rail on the block to the bottom of the screen. The oil pan on my '91 S10 Blazer 4.3L 4X4 is 9.250" deep, measured from the pan rail to the bottom of the sump. That was only 0.250" difference and I felt like 1/4" clearance from the bottom of the pan was not adequate, especially for a HV oil pump. Therefore, I bought and install a Milodon 18301 bolt on/press in style pick up for a oil pan that is 8.500" deep. With the longer (you say 0.300") HV pump and the shorter Milodon pick up for a 8.500" deep oil pan, it gave me between 0.400" and 0.500" clearance from the bottom of the oil pan. That is dead nuts on.

You may ask why go to the trouble to fit a HV oil pump? The reason is because The S10 Blazer 4x4 has plumbing for a radiator enclosed oil cooler with a remote oil filter mounted on the fender. All that adds restriction to the oil flow. Otherwise, I would have installed a std. volume oil pump and be done with it. The std volume pump is more than adequate for any high performance regular production street driven GM vehicle. I also installed a MSD HEI V6 distributor with a special melonized (hardened) distributor gear on the MSD 0.500" diameter distributor shaft. That gear will withstand the increased driving force caused by the HV oil pump.
 
#18 ·
There is nothing especially special about a melonized gear- they are commonly used in production engines.

You stated everything from there is no GM high volume pump to anyone who says they installed a high volume pump (for whatever reason) was either a liar or a fool who had been duped by an unscrupulous engine builder.
If some street squirrels claims they have a aftermarket high volume oil pump and are using a stock Chevrolet oil pan, they are blowing smoke or they have been told they have a high volume pump by the crook who built their engine.
If you retract all that and own up to your erroneous info (along w/the gem in another thread about installing 2.02" valves in 416 heads to use on a 305, for instance), all will be fine here.

There is room for everybody and we ALL make the occasional mistake, but what I can't condone is the statement- AS FACT- of BS. If it is said as, "I believe", "I think", or "In my opinion", etc. that's one thing. But a statement as if it is a fact- when in fact it is NOT fact- is another thing altogether.
 
#20 ·
Huh?

The correct numbers for the Melling pump that uses a 3/4" pick up tube is M155HV (high volume) and M155 (std. volume). Just because a pump has an inlet for a 3/4" pick up tube does not necessarily mean it is a "high volume pump". The length of the spur gears and pump housing determines wheather it is a high volume pump or not, not the size of the pick up tube.

A Melling M155 pump is likely what you have in your oil pan because those use a 3/4" pick up tube and they will fit a stock oil pan with from 0.375" to 0.500" clearance from the floor of the pan. The Melling M155HV pump will have from 0.000" to 0.200" clearnce from the bottom of the oil pan.

A 5 year old child with knowlede of basic math can see that at a glance. It has been substantiated that the Melling M155HV high volume pump is at least 0.300" longer than a M155 standard volume pump. The M155HV pump fit my 9.250" deep oil pan with less than 0.200" clearance..or less than 1/4" .

Maybe you have one of those rare "adjustable" oil pump pick ups. LOL Adjustable with a 5 lb. hammer.
 
#22 ·
Is it possible that the 4.3L S10 4x4 oil pan isn't as deep as a typical SBC pan?
I've never seen one so I wouldn't know. I thought this thread started off with questions for a 383...

On another note, at one time I had an older corvette SBC oil pan that wasn't as deep as a typical SBC oil pan. I never used it because none of my cars sat low enough to need it. THAT pan, I don't think, would have been able to handle a HV oil pump. It was shallow (the "sump" area of the pan was a little longer...actually past the half-way point of the pan). Other than that, the only other pan I know of that can't handle a HV pump is the early-nova front sump.
 
#23 ·
Retract your nonsense like Cobalt asked or go away. "There is an oil cooler on the S-10 and that adds restriction so that's why I used an HV pump" Get out of here. Chevy's have the best designed oiling systems going. If I had to do it over, I wouldn't use a HV pump, not necessary. And your B.S. about a melonized gear? As said before, nothing special...who cares? But the fact that you said putting 2.02 dia intake valves in a 416 head for a 305 was the hot ticket, you have proven that you have zero credibility. Have fun with those rocket sleds powered by 305's and 4.3's. I would say that is about all the power that you can handle.
 
#24 ·
cool rockin daddy said:
Retract your nonsense like Cobalt asked or go away. "There is an oil cooler on the S-10 and that adds restriction so that's why I used an HV pump" Get out of here. Chevy's have the best designed oiling systems going. If I had to do it over, I wouldn't use a HV pump, not necessary. And your B.S. about a melonized gear? As said before, nothing special...who cares? But the fact that you said putting 2.02 dia intake valves in a 416 head for a 305 was the hot ticket, you have proven that you have zero credibility. Have fun with those rocket sleds powered by 305's and 4.3's. I would say that is about all the power that you can handle.

Bowtie blocks have a totally different oiling configuration than a conventional GenI SBC. The melonized gear is different than a 20 year old gear, but the MSD gears produced in the last few years are a suitable replacement.
 
#25 ·
Pan clearance

It appears that some shade tree mechanics don't know what they are looking at. The pick up screen assembly in the link is a stock replacement pick up screen assembly for a stock M155 oil pump and can be used in a stock oil pan and it will have the correct clearance. However, GM does not and never did offer a high volume oil pump for any V8 engine. Thoise wefre all aftermarket parts and a stock pan does not have enough clearance. I called the head parts represenative at Melling and he confirmed that when I was trying to solve the problem.

Since you appear to have made it past the 5th grade, lets do a little subtraction:

Do you agree that a stock pick up screen is designed to be at least 0.375" from the floor of the pan ?
Do you agree that a M155HV pump housing is at least 0.300'" longer than a stock M155 oil pump (see photo)?
BTW. I measured a Melling Select 10552 high volume pump and it was 0.587" longer than a M155 but that pump has a thicker bottom plate for the extended spur gear shafts. I returned that pump to Summit.

Subtraction: 0.375" (minimum pan clearance) - 0.300" (extra length hof oil pump) = 0.075" (clearance from the floor of the oil pan). Do you think 0.075" is enough clearance? The solution would be to use a shorter pick up screen or a deeper oil pan and a longer pick up screen. . Since a shorter pick up is impossible, Moroso and Milodon has the solutions to this problem.

I used a Moroso 24360 pick up designed for a 8.250" deep pan and a Melling M155HV pump. That combination fit my stock 1991 S10 Blazer 4WD oil pan which is 9.250" deep. The pick up fit with 0.700" bottom clearance. The Moroso pick up designed for a 8.250" oil pan in my 9.250" deep oil pan made up for the 0.300" longer oil pump with 0.700" clearance, including the pan gasket.

I would not have used the high volume pump except for the radiator mounted oil cooler and the remote oil filter this is stock on the S10 Blazers e/w 4WD. Even though GM never used HV oil pump on any vechcle because of the oikl pan clearance issues, it is needed on any vehicle with a remote oil cooling and filter system. An oil pump needs the extra capacity of a HV oilpump to push the oil through the higher resistance to oil flow before the oil reaches the engine. I would not have never used a high volume pump otherwise, because a HV pump increases the turning resistance and increases wear on the cam and distibutor gears but only if the engine is built with the bearing clearances used for street driven vehicles.
 
#26 ·
MouseFink said:
However, GM does not and never did offer a high volume oil pump for any V8 engine.
Then what is CLICK HERE (obviously you didn't understand how to hold the cursor over the "HERE"- then left click- in my post above, that would have linked you to the same thing)?

GMPP (GM Performance Products) is a licensed part of GM- GM controls what does and does not get marketed under the "GM" name, just because Chevy didn't install a HV pump on a production vehicle (to my knowledge) DOES NOT mean they do not sell them under the GM banner.

Not every part that is bought for a modified engine is always going to be a "buy the exact correct part that needs ZERO adjustment/correction" to work! Even though the PU-on-a-HV-pump isn't one of these cases anyway. I always laugh at guys like you who cry, moan and piss because their freshly bought shiny new part doesn't just fall into place.

As hard as it may be for you to understand that- in the first place- there VERY OFTEN is nothing at all required to get 1/4" of clearance between the pan and PU, AND, that if additional clearance IS required in those few cases, the pan can be easily worked to supply the needed extra small amount of clearance- or the PU can be modded as required- IF it was required.

Since a shorter pick up is impossible
Says who?? Just because it is beyond YOUR abilities to hand fit a part- if it even WAS needed- does not mean it is anything even remotely resembling "impossible".

Moroso and Milodon has the solutions to this problem.
Milodon, et al have good products- but if you think the only correct way to use a HV pump is another PU, OR another pan- you are wrong. Period.

Here are some photos of an OEM PU. You may notice the design of this PU has the necessary stand-off built in to its design already. It would be considered to be correct as to the distance of the screen to the floor of the pan- even if it was physically touching the pan floor!

You seem to be laboring under the impression the the PU HAS to be exactly parallel to the pan bottom. Fact is, there needs to be the required clearance, but the PU doesn't function differently if it is at a small angle- and a small angle is all that would be needed (if any) to properly adjust the PU to the pan's bottom.





An oil pump needs the extra capacity of a HV oilpump to push the oil through the higher resistance to oil flow before the oil reaches the engine.
And with the bit of fallacy you provided us all in the last highlighted and quoted statement above, I will end this post.
 
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