[T2] engine oil pump / second oil cooler , engine improvement

[John Anderson]

Damn, if he really is machining the housing depth to match the length of the gears, that is impressive, as that is what sets the endplay of the gears.  I'd personally do it in a lathe not a mill, but I guess in todays world of easy CNC you can make round bore on a mill just as easy.
 
I'd still note the real wear occurs on the gears and on the cylindrical bores themselves, and aside for picking good used gears, there is nothing to be done about that, you can reduce the end play clearance, which is what you do on a T1 pump, and I'm impressed he does, but the radial clearance is what gets you in the end on a worn pump, then the body is junk.  And if the gears had worn enough then you can bet those bores being aluminum are worn 3X what the steel gears were.  If the gears were just loose end of tolerance from the factory, yeah the housing may be OK.
 
Still that is a lot of work for even $100-150 in my opinion, and probably ends up with something as good as new production if carefully matched.  O-ringing the outside is a bit gilding the lilly, maybe on a 5+ time rebuilt case, but stock pumps fit tight.  And a little judiciously applied orange Loctite that one used for the case parting line will fix the ones that don't for the life of the engine.
 
I don't know though, $50 and 20-30 minutes for a Schadek T1 pump vs more for a rebuilt T4, vs just inspecting your ole T4 and blueprinting what you can (the intermediate plate) is a tough decision.
 
John
 

________________________________
 From: Mike <manikmike at gmail.com>
To: Type2 list <type2 at type2.com> 
Sent: Wednesday, November 13, 2013 9:06 PM
Subject: Re: [T2] engine oil pump / second oil cooler , engine improvement
  

Hi,

There are, as mentioned, several options. For me: I'd have gone the route
of a T1 pump* and had the confidence to order one, if either of the two I
borrowed from local T1 fans fit my GE case well. Other folks may have
better luck. As I did not, and case fit was a common complaint for newer
ones, it seemed better to stick with stock that could be improved than
dicker around trying to find  T1 that fit when for a similar cost as a
Melling I could have a T4 that I knew fit and was appropriate for my build
reworked to potentially better condition. This does seem to be the case for
the unit I received.

*I looked into this because, as mentioned Raby promotes this and the mod
can be seen in his Bug Me vid, and other folks who's advice I trust
suggested it as a possibility - in the end, I went with what I believed
would best for my application.

Regarding the rebuild of the T4 pump by Phil, the process was described to
me as such:
- Clean exterior of pump body and remove thrust plate from housing using a
special puller that I built for this job.
- I mark the gears with a small center punch so I can index them at the
same point at reassembly if the same gears are reused.
- Remove gears and clean entire pump and pieces.
- Reinstall gears and check backlash to determine is gears are reusable, if
backlash exceeds factory specs then start looking for a good set gears. I
use what is called a gear tooth vernier caliper to check each gear tooth on
gear sets that fail the backlash test just in case one gear is worn more
than the other.
- If both gears are good than the next step is to mic the length of each
gear and then lap the longer gear to match the shorter, I also use a little
fixture that keeps the bore of the gear perpendicular to the lapped face. I
also remove the shaft that is pressed into the thrust plate and lap the
thrust surface and drill and tap the plate to help secure the shaft once it
is pressed back into the plate, this prevents the shaft from creeping
forward into the cam gear bolts which is a common problem on the type IV
pump.
- After lapping and deburr I set up the housing in a CNC mill again on a
fixture that will hold the housing firmly and flat for machining.
- These machining steps are confusing to some people (I asked for some
clarification but lost that response) so I will not go into detail so I
will just say that after machining the pump is reassembled, the end-play is
checked and the driver shaft ( the one turns ) is set to correct length.
- I am in the process of programming to machine an "O" ring groove around
the suction and discharge side of the pump housing, this "O"ring should be
a help in boosting the column and pressure of the pump by eliminating the
gap between the pump housing and engine case.

I had asked John at aircooled.net - he stated they had lost their machinist
to set up the T1 pumps for T4 engine apps. This was back in Spring, so that
may have changed, although the 26/ 30mm Schadeks on the website still show
an unknown return time to stock. Cheers, Mike