Originally Posted by Alan Roehrich
The base pump, the Melling M55, is a very weak casting, they will break just putting a stock Melling pick up in. This has been a problem for years, and has only gotten worse. I have a standing deal with the warehouse I buy my parts from that not even a stock rebuild gets an M55. Minimum is an M55A, which is a higher pressure pump.
The M55HV is also a different casting, although I have stopped using high volume pumps for most engines. It has seen changes over the years, it was pretty robust, then they took strength out several years ago, then, after failures and complaints, they went back to the old stronger casting.
At one point, even the high pressure and high volume Melling pumps were using cheaper powdered metal gears, and the gears failed. Now they say only the stock replacement budget pumps get those gears. Supposedly, the test for those gears is to mark them with a Sharpie, if the mark disappears, they are powdered metal gears, and should not be used in performance engines.
Melling has a Select line, those seem to do fairly well, they are held to tighter tolerances, use better castings, and better gears. They have several versions for small and big block Chevy applications.
Melling also has a new helical gear pump for the small block Chevy, it is supposed to have less drag, a smoother pressure curve, and less pulse variation. I have not tried one yet, I may. It looks good in testing.
I used the Moroso pumps for a while, as they were built to tighter tolerances than the Melling pumps, although Melling makes the base pump.
Schumann was making their pumps based on the old DynaGear castings, and using the nodular iron used for rear end housings. However, the last Schumann pump I got did not look as good as the older pumps. I have not bought one since, I switched to the cast steel Clay Valley Racing pump, and that is what all race engines now get.
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