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10552ST and 10555ST pressure problems

3789 Views 44 Replies 11 Participants Last post by  CNC BLOCKS N/E
The 383 I dynoed with high oil pressure using the 10552 ST oil pump was exactly what I thought was the problem. The bypass valve was to long and not exposing the complete bypass hole. I also have another engine with the same pump same problem.
I don't understand why I have to there home work for them. They told me not to take the pump ap
art it would void the warranty. I said really.
I have used probably 35 of the10552 pumps with zero problems. Now they said the 10552 ST they did change the cover HMMMMM
Here is a link to the dyno run
https://www.facebook.com/cncblocks.northeast/posts/pfbid0CWMCC5tUE7H6txU83MSpjAoU8FzbTU3S2kHjCUGtFtAoZSEQEPaEeG165yXwCig7l

PS
Good customer Jerry Brighthaupt saw my post on FB and took his 10555 ST pump apart and called me and found less the half the bypass hole was exposed. He was just getting ready to put the pump and pan on one his circle track engine. He was going to shorten the valve 3/16 of and inch which will cure his problem.

A big shop near him stopped using those pumps because of high oil pressure.


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Discussion Starter · #41 ·
I shortened the valve by ~ 0.095 - looks like the drawing I found on another site, where Melling showed when fully open the full diameter / shoulder should only protrode into the hole by ~ .030-.035.

CNC - For those if us who do not have the capability to machine down the valve (the SOB is hardened), what negatives do you see with just adding a 0.100 washer under the plug that retains the spring / relief valve ? That would be an even easier fix ? There seems to be plenty of thread on the plug.

Too bad this is an issue, without going to a significantly more expensive pump, this is a smooth pump.
1/2 cordless drill chuck the valve up in the drill and a belt sander works fine.
 

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Discussion Starter · #45 ·
Any update from Melling?
Nope I just fixed another pump where the customer took his pan off and brought me the pump and it was messed up
Any update from Melling?
Nope just fixed another pump where the customer had t much oil pressure

 
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