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Author Topic: M55A oil pump question revisited.  (Read 1658 times)
69Z28
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« on: April 02, 2013, 03:24:21 PM »

I know this has been talked about alot but I'm still trying to figure out what oil pump I want to use for my DZ engine. HBC advertises a Melling pump. I sent email to inquire about which model and they offer the M55A which they say they never had a problem with. I was thinking on using the Melling Select 10553 but was curious if Melling finally went back to using the older casting on the M55A versus the newer one that I heard was breaking in HP engines. Anybody have anything to add to this? HBC is asking around $75.00 for the M55A and the Selects are about $20.00 more at Summit and Jegs.

So far everything I have read dates back quite a few years on this subject.

Thanks guys for the help.
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GaryC

'UNRESTORED' 1969 Cortez Silver X33D80 Z28
69Z28
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« Reply #1 on: April 03, 2013, 01:07:36 PM »

I emailed Melling about all the old information online about the M55A oil pump and revieved this reply...

Yes, the M-55A is correct for the Z28. Standard volume high pressure bypass 
(78#)
Since 2008 the M-55A has had a robust HD casting.
Most info on the NET is BS.

George Richmond
Melling Engine Parts
Master Automobile Technician
(517) 787-8172 X 134
grichmond@melling.com

I'm hoping this is correct. I am going to order it soon from either Summit or Jegs. If anyone has recently bought one please let me know what you think.

Thanks
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GaryC

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« Reply #2 on: April 03, 2013, 01:25:38 PM »

It is my understanding the M55A pump went back to the heavy casting in early 2009, so with any current stock you should be fine. They do use powdered metal gears instead of billet gears though. The PM gears should not give you any problems unless you're dealing with a max effort engine.
Go for it!
Bob
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69Z28
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« Reply #3 on: April 03, 2013, 03:18:46 PM »

Nothing special. Just a stock rebuild. I may hit the occasional 6000 RPM but not too aften. I like staying in the 3000 to 5000 RPM range while cruising.



It is my understanding the M55A pump went back to the heavy casting in early 2009, so with any current stock you should be fine. They do use powdered metal gears instead of billet gears though. The PM gears should not give you any problems unless you're dealing with a max effort engine.
Go for it!
Bob
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GaryC

'UNRESTORED' 1969 Cortez Silver X33D80 Z28
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« Reply #4 on: April 05, 2013, 12:39:30 PM »

You might just use a stock oil pump and add the GM high pressure spring.  It is something like $4 and it makes sense if your pump is still good.  Most pumps have very little wear and they have a known good casting.  Just a thought.  Don't buy in to all the hype.

-Mark.
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69Z28
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« Reply #5 on: April 05, 2013, 02:03:49 PM »

Hi Mark. Been a while since we chatted last. I was going after the Melling Select 10553 until I did more current reading online. All the info online is so really old and needs to be updated somehow. Probably still lots of people out there that are afraid to use the M55A. I'm gonna give a go. The pump in the 350 LT1 engine in my car now has only 4500 miles on it. I'll have to see if it's a new or old unit. May even us it. This engine has my 302 oil pan and tray on it. No problems what so ever and it's seen 6500 RPM a few times. It's been a while since I drove the car so I can't remeber what the oil pressure is off hand.


You might just use a stock oil pump and add the GM high pressure spring.  It is something like $4 and it makes sense if your pump is still good.  Most pumps have very little wear and they have a known good casting.  Just a thought.  Don't buy in to all the hype.

-Mark.
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GaryC

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« Reply #6 on: April 09, 2013, 10:59:00 AM »

Gary,
You want 10 PSI for each 1000 RPM was the old rule.  I would look for that and run your known good pump if it passes the test. JMO.
Pull the cover off if you want to check for any wear.  I doubt you will find much.

-Mark.
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