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Melling oil pumps

10K views 48 replies 11 participants last post by  sqeezeit 
#1 · (Edited)
Just wondering if the pumps(m55,m55a) have the thin wall housings still.I heard that they dont , but a lot of previous thin wall stock still out on shelves for sale to people? Just wondering cuz all I need for mine is a standard volume pump and it would be nice to not pay double for a select series pump unless I have to?

P.S
And if anyone has any suggestions on making my 7qt pan thats listed as 8 1/4" deep fit a 3/4" pickup? Seems like all the ones that might work are $50-100, just for the pick up.
 
#2 ·
These days I'm not very happy with Melling oil pumps. I used an M-68 in a SB Ford, recently replacing it after less then 1500 miles. The lack of quality control is my main reason. Even after the miles driven, the clearances were either too tight or too loose depending on where they were taken. The cover to gear fit - about half of what it should be and the photo below shows what happened. Yep, Ford or Chevy have suffered with the current 'cost reduced' thin casting product. Now, was there any problem pumping oil? Not at the point the pump was taken out of service, but ya never know.



The pump on the RHS - everything dead nuts on OEM spec(a Ford Racing unit):



Dave W
 
#4 ·
well seems like im leaning more towards the select series like the 10552 I think,but cant seem to find a dam pickup that will work unless i go to a 5/8" pickup but dont want to but...Not only that but do the sizes or pickups listed for a pan like mine thats 8.250 deep meant to be used with stock size pump or a longer HV which are normally or almost .500 longer,so then in theory I would need a pickup for a 8" deep pan then right? Altimately I will have to measure but this crap is driving me nuts,just trying to get a pickup to work.
 
#5 ·
Here's a place that was recommended to me when I first found the problems with my Melling. Kinda expensive, but ....... SB Chevy - Oil System Components - Precision Oil Pumps

Another thing to watch out for, Melling pumps are often reboxed/rebranded as I found out when my first replacement try, a Sealed Power, turned out to have M-68 cast on it.

Oil pumps aren't something to economize to much with. A failure there is a quick engine death
 
#6 ·
Melling has not produced new oil pump pick up assembiles that will fit oil pans using Melling Select HV oil pumps. The Melling Select HV oil pumps have a housing that is .487" longer than a standard pressure housing. The spur gears are .300" longer and the bottom cover is .187" thicker than those used on a standard volume oil pump.

I an using a Melling 10552 oil pump on my '91 Chevrolet S10 Blazer 4x4. You must have a pick up custom made by a company such as KEVCO or you must redesign a Melling pick up assembly. In order to use a Melling 10552 oil pump, I cut and shortened the pick up tube on a Melling 259S pick up 1/2" so it would fit the Melling 10552 oil pump and my stock 9-1/4" deep oil pan with 1/2" bottom clearance. I also used a Jegs 23621 pick-up brace and wire welded the brace to the pick up tube, not bolted. Do not use a Melling bolt on pick up...examine one and you will see the reason why. Bolts have a tendency to come loose with engine vibrations and the Meilling bolt-on pick ups are weak where the tube is brazed to the bolt on plate. Engine vibration will cause the pick up to break and fall off, especailly if off-road or solid motor mounts are used.

The bottom cover bolts on Melling oil pumps are a intentionally weaker grade so they cannot be over-tightened and pull the threads in the cast iron oil pump housing. If you try to use "More's Law" on Melling oil pump bottom cover bolts you will break off the bolt heads.

More's Law....If the recommended amount is good...more is better.
 
#15 ·
Melling has not produced new oil pump pick up assembiles that will fit oil pans using Melling Select HV oil pumps. The Melling Select HV oil pumps have a housing that is .487" longer than a standard pressure housing. The spur gears are .300" longer and the bottom cover is .187" thicker than those used on a standard volume oil pump.

I an using a Melling 10552 oil pump on my '91 Chevrolet S10 Blazer 4x4. You must have a pick up custom made by a company such as KEVCO or you must redesign a Melling pick up assembly. In order to use a Melling 10552 oil pump, I cut and shortened the pick up tube on a Melling 259S pick up 1/2" so it would fit the Melling 10552 oil pump and my stock 9-1/4" deep oil pan with 1/2" bottom clearance. I also used a Jegs 23621 pick-up brace and wire welded the brace to the pick up tube, not bolted. Do not use a Melling bolt on pick up...examine one and you will see the reason why. Bolts have a tendency to come loose with engine vibrations and the Meilling bolt-on pick ups are weak where the tube is brazed to the bolt on plate. Engine vibration will cause the pick up to break and fall off, especailly if off-road or solid motor mounts are used.

The bottom cover bolts on Melling oil pumps are a intentionally weaker grade so they cannot be over-tightened and pull the threads in the cast iron oil pump housing. If you try to use "More's Law" on Melling oil pump bottom cover bolts you will break off the bolt heads.

More's Law....If the recommended amount is good...more is better.[/
QUOTE]

Why can't u just use one from moroso(24360)or milodon(18214)?its made for pan just like mine.
 
#8 ·
UPDATE ON THE JEGS OIL PUMP PICK UP RETAINER

Apparently Jegs Performance Products 23621 oil pump pick up retainer for a 3/4" pick up tube is either out of stock or discontinued. The Jegs 23620 pick up retainer for a 5/8" pick up tube is still available. The pick up retainers are actually made by Jegs Performance Products and they may have only made a limited number of them. The retainer for a 3/4" tube was probably more poplular and they have sold out and they have no plans to make any more.

If you wire weld the retainer to the inlet tube, you can use the Jegs 23620 for a 5/8" tube on a oil pump with a 3/4" inlet tube. A long pick up tube must use a retainer of some sort.
 
#9 ·
Melling Weak design pumps.

I already dealt with this issue. Had a few of these weak casting m55 SBC pumps. Easy answer is to use a M77 pump for a BBC. They bolt up, are smoother and more reliable. This does require you to to modify / shorten the drive rod/shaft. and the pick up but they work very well in a SBC oil pan. Also, I don't know who makes the MILODON pumps but they are very heavy casting with no issues and only cost a few dollars more.
 
#10 ·
Moroso 22090 oil pump driveshaft is 0.125" shorter than a BB Chevy driveshaft and is designed to use a BB Chevy oil pump on a SB Chevy engine. I considered using a BB Chevy oil pump on my 4.3L V6 but during a trial fit, I found that the inlet of the BB Chevy pump was facing towards the rear of the engine and was too close to the back of the oil pan on a V6. That is because the engine is shorter by two cylinders.

A Melling Select 10990 oil pump is a BB Chevy V8 style oil pump that is specifically made to use on a SB Chevy V8 engine. It comes with a special drive shaft.
 
#14 ·
2 things I have to confirm then I found 2 or more that will work, both milodon and moroso have them. First is does anyone know if the melling M155hv the same height as the select series 10052 and second thing is the M155hv have the thin casting as the m55 ect..
 
#21 ·
So if you have a static running system building 60psi with all the clearances and cavities full of oil. You then open add an additional demand. For arguments sake a 3/8 hole downstream at the end of the system. What happens to the oil pressure?

It drops until the volume increases to a point that it can begin building pressure again. Without adequate volume the pressure won't build enough to allow the bypass to open.
 
#24 ·
Closed loop vs open loop
Length of lines
Diameter of lines
Number of elbows/fittings
The magnitude will vary with these parameters but the type of effect will not- basically for this discussion these parameters are meaningless and can remain unitless so as to not muddy the waters. No matter what, an inline oil cooler placed after the pressure regulator is going to reduce flow- that's the key element to notice.
 
#27 ·
All my years of running SBC's of 3.48" and 3.75" strokes up to and over 7500 rpm...and I've only ever used 5/8" pick-up M55S or M55HV pumps...and I've never had an oiling issue.

I've broke or burnt pistons, burnt up rocker balls with too close to max spring pressures, pulled rods in half part way up the beam...but I've never lost a bearing.

I just guess I must be the luckiest SOB alive, AP.

I deburr and port the pump and rear main cap, but that's it....sometimes windage tray and rear cap baffle, depending on what the pan already has for features and depth/capacity.

GM did most of the work when they designed a good oiling system for the SBC.

The OP certainly isn't pushing the performance envelope so hard that he needs to worry about pick-up diameter, as far as I'm concerned. If what he has built will have a problem with 5/8", 3/4" wouldn't make a bit of difference.
 
#28 ·
And reasoning like this would have kept us riding around in model T's.

Why run a part that is inferior to something GM started installing in the 90's? There's nothing to be afraid of when it comes to a better oiling system.

That being said- porting the pump will do more good than running a larger diameter pickup- but that takes time and tools, something not everyone has access to.
 
#29 ·
I know I have no race motor but just want to get the best I can with money involved of couse . With all that's been said, I agree could use 5/8" pickup I think and be fine, just figured 3/4 might be better but now trying to get pump and all to work. I still don't know if I should go hv or not and that depends on able to get one cheaper then select series if possible. Still don't know if the m155 is or had the thin casting issue as others did? Now with that said I have cleaned up main cap inlet but not pump yet until I decide on one. With all the talk about braking cover bolts or them coming lose how do u install pickups properly when the mount to cover with the bolts. Plus how do u check pump clearances. Sorry for long post
 
#31 ·
Loc-tite on cover bolts does the trick.

Pump clearances are checked with feeler gauges.

I have no idea on the thin pump issue, as I have about 4 of the old style left, bought years ago, and haven't used them up yet.

I have seen links posted on other race forums to the Milodon pump, that they currently sell, and it is a heavy casting.
 
#32 ·
I would use what I have already which is 7qt pan and matching pickup but don't know if that's when used with standard size pump I'm guessing so that's what got me looking to begin with, plus I figured 3/4" pickup might not matter but it shouldn't hurt either. But at same time if I get other pickups there not cheap.Now trying to get and decide on pumps. I figured checking clearance with feelers but how?
 
#40 ·
I figured checking clearance with feelers but how?
You remove the cover bolts, slide the cover to one side, and use it as a "straight edge" to check clearance between the cover and the top of the gears using feeler gauges. Too little clearance, sand the ends of the gears on a flat surface ...too much clearance, sand the pump main body where the cover bolts on
 
#34 ·
Precision Oil Pumps

You know for a extra $60 bucks that's great for peace of mind :thumbup:

$99 for a gone through M55

Yes sir,but I have no issue with buying one.But if the castings are not thin/weak anymore like sum say then why buy a $100 one if a $50 one works just as good for the most part.Just trying to find ones that arent and since there can be boxes of old thin ones still out there I wont know it until I recieve it or someone opens box for me to confirm it before I buy.I have none to look at before purchase myself.It really is frustrating not being able to go to store and look at.
 
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