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Discussion Starter · #22 ·
OK, so "old wives tale" to much oil pressure will wipe the bearings off and the crank will do the rest?
Some times with a lot of constant high oil pressure it will hurt the Dist. and cam gear. this has already happened to someone on another site.
 

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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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Discussion Starter · #25 ·
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
: 11614403, member: 211146"]
Would it not be worth running the titan pumps to eliminate the hassle and have psi adjustability? The new owner is a fantastic guy and offers a great product.
[/QUOTE]

The Titan pumps are nice probably better then the ST pumps right now.
 

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Discussion Starter · #26 ·
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

I actually found a 10552 non ST pump that will be here in Tuesday to compare against.

Not getting any answers from Mellings right now and they have had a week to review whats going on.

My guess is they shortened the casting where the plug goes in orrrrr they are using the a valve that is to long. If it was shorter it would clear the bypass hole.

This seems to be a bigger problem then I thought I have got alot of emails and calls PM's ETC. There are a lot of ST pumps and running to much oil pressure for some reason.

One guy has a 10553 ST which is stock volume and 10/30 Mobil 1 oil at 3000 RPM he is at 100 PSI.

On one forum one guy hurt is Dist gear and probably the cam gear as well.

I have used probably 35 or so of the 10552 NON ST pumps with the yellow spring always been right at 62 too 64 PSI
 

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: 11614403, member: 211146"]
Would it not be worth running the titan pumps to eliminate the hassle and have psi adjustability? The new owner is a fantastic guy and offers a great product.
The Titan pumps are nice probably better then the ST pumps right now.
[/QUOTE]
I’m surprised you haven’t heard any news back yet. A week is plenty of time to figure out what went wrong. If mellings doesn’t get it sorted out pretty quick I’m sure a lot of engine builders are going to look elsewhere. I mean if you build and machine engines for a living you can’t keep dealing with the time and cost incurred redoing oil pans and gaskets. It’s a lose for everyone

As for titan in CA, Really respect when someone a great part, but when they are as good to deal with as Shawn the new owner of titan is……they are a notch above the rest in my book. Makes me wish the guy made more parts.
 

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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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Discussion Starter · #29 ·
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 .
I should have my non ST10552 in today and see what the difference is between the two I bet the bypass hole is fully exposed on the old pump. We will see.

Or the valve is to long. I had two engine builder that shortened the valve and the pressure was fine after that.
 

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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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Discussion Starter · #31 ·
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 .
Still waiting for my 10552 non ST pump to arrive.
 

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Discussion Starter · #32 ·
Well I got my 10552 NON ST pump in to compare against the 10552 ST pump. And I was right on my conclusion. If you look at the first cover off the 10552 there is about .030 of the valve in the bypass hole.
Now look at the new 10552 ST pump cover the bypass valve is covering up appox .135 of the bypass hole which is causing the problem with high oil pressure problems.
Mellings engineers overlooked that the new cover seems to be more narrower then the older cover causing this problem.
The cure is to shorten the valve to clear the bypass hole.
There seems to be a lot of engines running with high oil pressure. Oil filters blown off on the dyno and distributor gears being chewed up.
The cover on the right is the old design and they have changed the new cover quite a bit. Along with a tiny bleed hole for the pilot of the drive gear.
One of my customers had to shorten the valve 3/16 of an inch and oil pressure was fine on a 10555 ST pump.
Some of the earlier ST pumps have the earlier cover and don’t seem to have this problem.
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Discussion Starter · #34 ·
My engine builder caught the ST pump with hi pressure with the drill. He was able to change spring and was good. This was 4+ years ago tho.
That pump probably has the older cover which does not seem to be a problem.
 

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Hello guys Interestingly enough, I threw a belt and had to rebuild one of my 421s in my boat, and stumbled on this when I was looking for a new pump. Had 2 pumps I bought back in 2020 when I swapped oil pans. These had a casting number of GL5 & 216, and the one I bought this year (I discovered a crack in the casting), had a cover casting number of GL2 & 214. BOTH look like the above photo from CNC blocks & covered a lot of the relief hole, as shown above, so I was concerned, as these engines live at 5800 to 6000 rpms for miles and miles at a time. Funny thing is with both my dart SHP blocks, if you take the oil pressure down low by the filter, the reading goes over 100 psi with just a poke of the throttle, but up top by the intake, it is significantly less, so I am going to shorten the valve ~ 0.100" as well. When pulled apart (I have a lunati cam with everwear gear, the gears looked good luckily - Ill have to look at the other engine).

Instead of shortening the valve, another quick fix would be to simply put a washer under the head on the plug that retains the spring (there is plenty of thread).

7/26/22 - Anyways sent an email to Brian @ melling for a status, and he said some folks are shortening ~ 0.100, but engineering has not tested / validated that change yet.
 

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Some times with a lot of constant high oil pressure it will hurt the Dist. and cam gear. this has already happened to someone on another site.
My 383 had the ST pump and has always had very high oil pressure (~60-70 idle & 100ish above idle). It bothered me but like an idiot I didn't do anything about it. Well, I lost a head gasket (unrelated) and had to limp it home (nearly 200 miles in the middle of the night). On tear down (it got real hot a few times and the oil was a milkshake so I wanted go through it) I noticed some pretty severe cam gear wear, absolutely enough wear at ~14k miles that I would not re-install. It was a Howard's HR that was okay for stock distributor gear.

Other wear surfaces all looked good but I don't trust the 40 over block after several high heat cycles so I built a 400 for it and will look for a replacement block to reuse the good rotating assembly. I'll follow this to see about modifying the pump first or just replace it but the pick up (brazed on) is right for the deep pan so I'd like to reuse it if this works out.
 

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Discussion Starter · #37 ·
My 383 had the ST pump and has always had very high oil pressure (~60-70 idle & 100ish above idle). It bothered me but like an idiot I didn't do anything about it. Well, I lost a head gasket (unrelated) and had to limp it home (nearly 200 miles in the middle of the night). On tear down (it got real hot a few times and the oil was a milkshake so I wanted go through it) I noticed some pretty severe cam gear wear, absolutely enough wear at ~14k miles that I would not re-install. It was a Howard's HR that was okay for stock distributor gear.

Other wear surfaces all looked good but I don't trust the 40 over block after several high heat cycles so I built a 400 for it and will look for a replacement block to reuse the good rotating assembly. I'll follow this to see about modifying the pump first or just replace it but the pick up (brazed on) is right for the deep pan so I'd like to reuse it if this works out.

I would get a hold of Mellings they have insurance for there mistakes, You not the first with distributor gear wear problems.

Left 5 messages with Melling and no return calls to date.
 

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Discussion Starter · #38 ·
Hello guys Interestingly enough, I threw a belt and had to rebuild one of my 421s in my boat, and stumbled on this when I was looking for a new pump. Had 2 pumps I bought back in 2020 when I swapped oil pans. These had a casting number of GL5 & 216, and the one I bought this year (I discovered a crack in the casting), had a cover casting number of GL2 & 214. BOTH look like the above photo from CNC blocks & covered a lot of the relief hole, as shown above, so I was concerned, as these engines live at 5800 to 6000 rpms for miles and miles at a time. Funny thing is with both my dart SHP blocks, if you take the oil pressure down low by the filter, the reading goes over 100 psi with just a poke of the throttle, but up top by the intake, it is significantly less, so I am going to shorten the valve ~ 0.100" as well. When pulled apart (I have a lunati cam with everwear gear, the gears looked good luckily - Ill have to look at the other engine).

Instead of shortening the valve, another quick fix would be to simply put a washer under the head on the plug that retains the spring (there is plenty of thread).

7/26/22 - Anyways sent an email to Brian @ melling for a status, and he said some folks are shortening ~ 0.100, but engineering has not tested / validated that change yet.

Shortening the valve is your best bet its an easy fix. There are a lot of problems with this new cover design in any of the ST pumps using the new cover.
 

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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.
 
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