So I went and purchased one of the Type 4 CNC oil pumps off the Samba. I've been looking for a good used Type 4 pump with limited sucess. I did start a thread long ago looking into what it was going to take me to rebuild a pump by mixing and matching parts and/or by remachining some housings to make serviceable parts. This is another case were procrastination may have paid off.

Here's the old thread:
http://www.914world.com/bbs2/index.php?showtopic=338311

New CNC Pump Overview:
30mm gears vs OEM 24mm (not thrilled with 30mm gears for a stock rebuild but will have a use for this in the future).
Idler shaft is supported in double shear just like OEM
Fit and finish of parts appears to be good visually
Idler gear shaft is not pinned to the housing - same as OEM but I view this as needing to be fixed

I still need to sit down and do some real inspection measurement of flatness, gear clearances, etc. Looks to be a very viable direct replacment for NLA Type 4 pump.

I will modify the idler shaft by pinning it to the housing to prevent migration that plagues overheated OEM pumps that are in circulation.

Here's the pictures of it:

Front

Click to view attachment

Back
Click to view attachment

Disassembled
Click to view attachment

Idler shaft as received - not yet pinned

Click to view attachment

Would like to know your final results after you do your deep inspection. I’m building a 2056 and will be in search of a different pump

That looks very promising

And better than my (steel) Melling that refuses to stop dripping

This is an interesting design. I worked as a design engineer building small fixed clearance gear pumps similar to this pump for about 10 years. Those pumps went to 3000 psi and had a few differences from the design shown here. They did have hydrodynamic bearings as well similar to this design, however both bearing races were allowed to sweep oil. This was needed due to the high working pressures which would build in the bearing race if it were not relieved, causing the gear to dig into the opposing wall due to those forces. With the pressure being so low in these pumps this is not a problem for the oil film on the opposite side to handle.

What is also interesting is the little depression between the two centers of the gears. We called this an untrapping pocket and it is needed due the abrupt reduction in volume when the two gears mesh. Since this is an external gear pump, all of the flow occurs on the outside of the pump and the center where they mesh is simply a seal between the high and low pressure sides of the pump. Without this little relief to allow oil to escape while the gears mesh, your pump would sound like it has gravel in it due to the exceedingly high velocity of oil as it squirts out.

There, now you know more than you will ever need to about gear pumps.

@jcschuf1

Cool. I learned why those little divots between the gear mesh are there. Thanks!

I apologize for the lazy question.

Does anyone have a link to these new pumps for sale?

I’ve resealed mine so many times.
It might be worth upgrading (even though I hate pulling the motor again)

TIA

@brant

Hopefully, I'm not breaking some rule by posting this, otherwise would have included it in OP.

https://www.thesamba.com/vw/classifieds/det....php?id=2450773

Not cheap vs. Type 1 alternative but priced resonably given cost for NLA Type 4 pump assembly. Likewise seemed reasonable to me for the time spent on devopment, fixtures, CNC work, and materials. Even though some components like housing, face plate, and idler gear can still be obtained as OEM NOS component parts, they are stupid expensive. The Type 4 driven gear is truly NLA and I've never found a source for them.

Consider that a 911 oil pump is about $1200 and suddently it seems like a bargain. I intend to do a side by side measurement to known good Type 4 pump. I'll post results after the weekend if you want to know more before you order one.

thank you!
and thanks for taking the time to compare them
brant