clatgeo

I spoke to George Richmond at Melling today and he told me the best oil pump for a 1970 rebuild LT-1 engine was the Melling M55A oil pump with the yellow relief spring.

What relief spring would you use?

babbah

Yellow

GOSFAST

For years now we've been using the M-55 pump with the spring from the M-55HV pump.

When you use the spring (part #M-99015) in the M-55 you have the M-55A, this is the equivalent of the OEM G.M. pump's found in the "DZ" 302's and your LT-1.

George's (Melling's) M-55A's are listed for "for use with H/Perf. and Spec. Hi-Perf.", it is how it reads in their catalog.

We actually buy the M98015 springs in "bulk", 100 at a time. See the photo below! The springs are ALL a pink/purple color, the camera makes some look black. This setup yields 60# pressure.

Thanks, Gary in N.Y.

P.S. I would add for some years I had been "working" on George and Melling to package a similar BBC pump setup. All it would be is an M-77 pump with the spring from the M-77HV. This spring number is M77020. We've been doing this for years, also buying in "bulk"!

Solid LT1

I would NOT use a modern M55 pump in any motor I build! Melling has cheapened the quality of that pump and GM had them make changes to the casting years ago that weakened the pump that in no way resembles the M55 pump made 25 years ago. The present pump has powdered metal gears and is not a quality product.

I use the Melling "M select" series of pumps in my builds that have the HD housing casting and billet steel pump gears. The Melling part number 10553 would be the std volume pump in that series of pumps.

Use what you want, I know I want quality parts in my builds, I won't use Sealed Power forged Pistons anymore either as they now produce them in India but, if you want to stick with original manufacture parts be my guest.

MotorHead

If you can get the M55A oil pump with the correct casting that is all you need. This pump is good for a mild 350ci all the way up a 427ci small block. This is the so called "Z28" pump and all it is a basic small block pump with about 10% more pressure

Dirty Dalton

Interesting. I did some looking, spurred by this conversation - the 55 and 55A are in the $50 range, but those (select, as noted above) in the $100ish range seem to be thought of more highly. The Chevy pump was, I think, $120ish, retail. Then there are the high pressure/high flow choices...

I'd love to hear some more thoughts as I'm going to be pulling the trigger on this one in the near future.

Solid LT1

I've built around 20 LT-1s/Z28 302 motors in my life. I run my motors pretty hard, I don't use cheap parts in my builds, I'll use a $99 oil pump over a $47 one anytime if I think the part will add reliability and longevity to a $4000 engine rebuild. If I were building a motor for a Impala Station wagon sure the M55 would be acceptable but, for a solid lifter Chevy going to a 6500RPM operating zone....I won't use one! The M10553 also comes with the HD drive shaft with a steel coupling sleeve, if you want your LT-1 NCRS correct, that won't work, you need the "correct" nylon sleeve. You should also hunt up a nylon timing chain too, I use True Roller timing chains myself in my builds. I guess it depends on what you intend to do with your Vette when the build is complete.

Video of M10553 pump in action, over 10K miles on the build now, 7200RPM rev limit still being reached on most drives.

Link:

Dirty Dalton

I'm following up with Melling, I'll pass along what they suggest.

MotorHead

I use the "Z28" oil pump on my 600HP 427ci small block and rev it to 7000RPM with no issues, that's tall I need to know

Solid LT1

Be sure and cover the subject of the pump gear material, in the M55 it is powdered metal, the M10553 is billet steel, just like GM used when the LT-1 was built back in those "olden days". The billet gears will be able to digest a small amount of debris, the powdered metal will crack and fracture if they encounter any substantial debris.

There are many that believe the late model powder metal rods are the ultimate, even GM uses them in the LS motors until they get really serious with the LS7/9 motors. I've seen more than one late model Vette/truck motor crack a powder metal connecting rod, I won't use them...I have a LS3 build going on right now, powdered metal rods OUT! Forged connecting rods IN!....I might even blow the budget on eliminating the powder metal main caps for some LS9/7 caps if I can find some cheap enough now that I have access to a Hurco align boring machine.

Solid LT1

I rev most of my 302/LT-1 builds to well over 7K RPMs when you going the high side of 7500, that can separate the men from the boys in motor building/parts quality. If I'm building a solid lifter motor, I build them to RPM because that's where they shine.

Gale Banks 80'

For my last Motor build I read that the GM LT-1 Pump is still the best after all these years so I bought one directly from GM. When I opened it up I really didn't like what I saw as far as machining it looked pretty ruff. So I bought the Melling, I believe it was a 55, and it was night and day better looking. The so called LT-1 Pump got shelved. Its been pumping dust ever since.

Jebbysan

The 55a is a great choice.....they did cheapen the casting a bit in 2007.
The 10553 is an excellent choice as well.....it is obviously a stouter piece...albeit more $$$$$$....though I know of 0 people that have problems with the M55. We are just not racing.
I agree though with SolidLT1 as far as a 10553 being needed in a 7500 rpm engine...but 99% of gen 1 small blocks, including my own, run to 6000 or so....
The pumps are listed as "high pressure".....this is a bit of a misnomer.
Pressure is in direct relation to bearing clearance....the pump has no idea what pressure to push the fluid....it is 100% restriction that creates the pressure.....I think what the label means is the pressure blow off spring is stouter.....blowing off at a higher pressure.....
Never use an HV in a street application....just too much oil and it is hard on the shaft and distributor gears.
Make sure for $6 that you install a stud to install that new pump...much better torque reading and keeps the cap from galling or pulling threads...which is a bad day.

Jebby

7t9l82

I used the melling select pump in mine because of the better gears and the feedback I got from others.
But it is true in most cases it boils down to the more money than brains club.
No matter which way you go melling has always built a solid pump.

cv67

no need even on an LT1 stock with a good spring is plenty;they are usually about done by 6k or so anyway
Ill never use a HV pump again either just not needed;1970s thinking
I have one of the "bad" pumps in mine so far no problems...a select in the box in case

take your time and follow instructions if using a stud

Solid LT1

LT-1 signing off at 6K? Something's WRONG with the "tune up" on any solid lifter Chevy whether it's be a big block or small block if it won't easily clear 6500RPMs. How many LT-1s have you owned?

My 1st Vette was a C-60 equipped 72 LT-1 when I took it to the drag strip after carefully setting all the valves, rebuilding the carb with a "trick kit" and replacing all the ignition components (rebuild distributor and recurve it) that Vette quickly spat all the drive belts off on my 1st low 14 second pass, I heard it rattling a little through the lights thinking I need to back off the timing only to the watch the water temp climb on the return road to the timing booth. Get it back to the pits and it was puking water by then with no water pump being driven. My fix was installing a deep groove alternator pulley. I ran that LT-1 to 14.06@103MPH in 3rd gear through the lights, it had 96,000 miles on it at that point.

I forgot to address the OP question....solid lifter motor? Put the 70LB "pink spring" in the pump! If it's a hydraulic lifter motor I guess I could see running the yellow spring. Hydraulic cams are sac-religious in my book of LT-1....unless it's a C-60 equipped 72....then I can understand because trying to adjust those valves under the compressor is a complete PITA!

If your doing a high RPM wet sump build....now you need to upgrade to the latest "Shark Tooth" design from Melling....looks like a great piece but not needed by 99.7% of most people on this forum. Plus it's a $185 oil pump....but, reliable speed costs $$$ how fast do you want to go and how long do you want to go that fast.

cv67

meaning not making much power past that point
Ive had one or two

427Hotrod

The "Z-28" pump is usually fine for just about anything we're talking about as far as performance.

This was some interesting back to back testing done a few years ago. They even ran a test with a BBC HV/HP pump (should be terrible right?) and it produced surprising results. Folks have used them for years on small blocks....not saying it's necessary...but they work. You jave to click on some links within the article to see the dyno results and oil test results...but worth reading.

A HV pump does nothing special except achieve higher pressures at lower RPM. The pressure is still determined by the spring. They help when you have looser clearances and want to keep low speed pressures up. A stock pump can put out 100+ psi easily with the right spring. The idea is to not be on bypass constantly while doing normal driving. It should increase when you stuff your foot in it.

I've never had a worn distributor gear in my life...been running Melling HV pumps with lots of pressure for years on stock gears. If gears are wearing out..it's a cam gear/dist gear interface issue...not the oil pump.

http://www.hotrod.com/how-to/engine/...evy-oil-pumps/


JIM

babbah

I've had a Melling 77HV in my BB for decades. No issues at all to date.