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10552ST and 10555ST pressure problems

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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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hi
WOW
100 psi on the dyno sheet on an engine that sees 6000rpm so,, 60--70psi would be ok and idle 20psi +.

About to assemble
Just checked my 10552st pink spring
Piston travels freely in bore

##### Fully retracted piston covers 20--30% relief hole

Details
It looks like 3/16 inch needs machining from bottom of relief piston so it opens hole up a bit more .
## Does shortening piston actually cure the problem when running .0025 mains clearance
or is it more about hole placement ???
Are people having success doing this mod . Oh yea please state what spring your using .
EG pump comes with 3 springs pink installed ....
 

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hi CNC
yes I do no how an oil pump works
interested in expectations for idle pressure , yes I am running larger clearances .
Oh I am aware that full pressure comes on after idle and if the pump is flowing far to much oil it will find the semi blocked relief hole a restriction and then the engine oil pressure will rise and potentially run away and find its own maximum .
Funny I`ve always seen oil viscosity influence engine oil pressure ,of course until it reaches pressure relief setting .
Oh yea most oem quote at what rpm an engine achieved its max pressure .
 

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hi
1/ Concern about over pressurizing
2/ potential issue is piston is closing pressure relief hole by 20-30%

Specification of piston [main circular body ] protrusion into relief hole is .030 inch

Investigate [ measurement from Melling ]
1/ relief piston total length is 1.625 inches
2/ relief spring plug total length .500 inch
spring plug threaded section = .length 370---..380 inch
****If the dimensions are correct the housing has the hole drilled in the wrong position ? TBA.
 

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hi
I suspect core shift in the casting . I have now checked all my pump factory specs and the location of the hole is the only thing left that can be incorrect . What concerns me is
1 / springs have a very complex design ,ie will shaving the piston work ?
2/ will coil bind [once machined ] occur and not let the piston to fully retract anyway ??
 

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hi
The hand drawn pic is demonstrating ...
max allowable protrusion of piston into relief hole is .030 [from Melling]
Shows how far out the screw plug is when piston is correctly installed

This plug ""clearance/gap "" is the problem and shows how far into the hole the piston protrudes
piston and plug are correct dimensions
=housing hole is incorrect

**** Melling are reviewing this at this very time .............
 

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10552ST spec clearances and bolt tensions

CLEARANCES
gear tip to housing .002---.005 inch
gear side to cover plate .004---.008 inch
Gear backlash .076----.772 mm

Tension
Cover plate 4x bolt 80 in/lbs or 9Nm --12Nm
Bolt Pickup 2 bolt 80 in/lbs factory loktite
*****IM Opinion is apply loktite and wire tie all bolts

Dimensions
piston tot length 1.625 inch
piston narrow sections .531 inch

Screw in plug
.500 tot length
gasket face to tip .370--.380 inch
 

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hi latest is

Screw in plug for pressure relief spring is likely incorrect

Oil relief hole positioning check in casting
1/ cover plate laid machine face down
= hole vertical / height 22.89mm to centre of screw plug/relief hole

2/ cover plate standing on edge , with machined face pointing away from u
oil pickup to the R/H/S
top left centre of mounting bolt
horizontal measure ment to centre of screw plug
= 29.85---30.10mm

Testing and review is being done as we speak .
 

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hi
The screw in relief spring plug was made longer .
WHY the threads stripped but ,probably the person fitting pump DOH !!!! caused the issue
This resulted in a production change
Then the issues started

NB was the recess depth changed for the spring seat . ?? This whole situation is being looked into .
1-2 approx wks for an outcome .
 
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