Melling Oil Pumps...part #?
Thread Starter
Le Mans Master
Joined: Jul 2000
Posts: 5,012
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From: OKC OK
Melling Oil Pumps...part #?
This is a follow up question to this thread... http://forums.corvetteforum.com/zerothread?id=666757
Which of these two pumps should I get?
#M-55HV SBC High Volume $21.95
#M-155HV SBC High Volume w/ 3/4" inlet $39.39
Thanks again
[Modified by LT4POWR, 1:11 PM 10/23/2003]
Which of these two pumps should I get?
#M-55HV SBC High Volume $21.95
#M-155HV SBC High Volume w/ 3/4" inlet $39.39
Thanks again
[Modified by LT4POWR, 1:11 PM 10/23/2003]
Race Director
Joined: Sep 2000
Posts: 17,298
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From: The Top of Utah
Re: Melling Oil Pumps...part #? (LT4POWR)
Why that one over the other one?
RACE ON!!!
[Modified by CFI-EFI, 8:12 PM 10/23/2003]
Le Mans Master
Joined: Feb 2000
Posts: 9,715
Likes: 27
From: Kempner Texas
Re: Melling Oil Pumps...part #? (LT4POWR)
Why that one over the other one?
Depends on who you believe.
Some say that only Olds and Pontiacs need the HV pumps due to the design of those engines and that the SB Chevy runs just fine with the standard volume pump. These folks also claim that a HV pump can suck an oil pan dry when high RPMs are sustained. The theory is that there isn't enough time for the oil to drain back to the pan so, eventually, a lot of oil is sitting under the valve covers and in the lifter valley and the pump pickup sucks air.
Others install the HV version without exception.
I've always built my engines using a HV pump and have never had a problem, even when running 8500 RPM big blocks in the 1/4. The 3/4 inch pickup is just another plus to me.
I just stick with what works and would rather not fight about this one.
Jake
Race Director
Joined: Sep 2000
Posts: 17,298
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From: The Top of Utah
Re: Melling Oil Pumps...part #? (JAKE)
Vader86,
As you probably know, but for the benefit of everyone else, the M55A is a high pressure pump, with the stock volume output. The pressure of any of these pumps may be altered by shimming or replacing the pressure releif spring. The HV pumps are made from a different casting. The gears are longer and therefore the body of the pump is longer to accomodate the gears. Longer gears move a greater volume of oil per revolution. Hence, the name.
I was having a problem with my pickup truck, that I thought was being caused by the high volume pump. Driving down the highway at 3500 rpms, or above, the lifters would start clicking after a while. I attributed it to the HV pump, as above. I pulled the pan and changed the rod bearings and the pump. I still have the same problem. What ever the problem is, it isn't caused by a high volume oil pump.
One cannot argue with what works. Good luck, and...
RACE ON!!!
As you probably know, but for the benefit of everyone else, the M55A is a high pressure pump, with the stock volume output. The pressure of any of these pumps may be altered by shimming or replacing the pressure releif spring. The HV pumps are made from a different casting. The gears are longer and therefore the body of the pump is longer to accomodate the gears. Longer gears move a greater volume of oil per revolution. Hence, the name.
These folks also claim that a HV pump can suck an oil pan dry when high RPMs are sustained. The theory is that there isn't enough time for the oil to drain back to the pan so, eventually, a lot of oil is sitting under the valve covers and in the lifter valley and the pump pickup sucks air.
I just stick with what works and would rather not fight about this one.
Jake
Jake
RACE ON!!!
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From: Somewhere nowhere
Re: Melling Oil Pumps...part #? (SkarodoM)
>>On an aside, alot of guys say it'll suck the pan dry... but the bypass is at the pump. <<
could you explain that a little more pls...
also to LT4, what are you doing to the motor?
did it fail somehow? (I keep tabs on LT4 failures and how & why)
could you explain that a little more pls...
also to LT4, what are you doing to the motor?
did it fail somehow? (I keep tabs on LT4 failures and how & why)
Race Director
Joined: Sep 2000
Posts: 17,298
Likes: 33
From: The Top of Utah
Re: Melling Oil Pumps...part #? (larryfs)
Larry,
The "bypass" is also called (and is) the pressure relief valve. It only bypasses when a certain pressure is reached. That pressure is determined by the spring. This in no way, would prevent the pump from emptying the pan. Good luck, and...
RACE ON!!!
The "bypass" is also called (and is) the pressure relief valve. It only bypasses when a certain pressure is reached. That pressure is determined by the spring. This in no way, would prevent the pump from emptying the pan. Good luck, and...
RACE ON!!!
