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Ah, it's been so long...

Have a real question/conundrum,
And figured why not do like we always useta and ask on the STF?
Still some of you guys around, right?

So, I'm doing a Bus motor for a friend,
And it turns out the core was an old Raby 'Powerstroke' from 2002 or so.
It was CIS, if that gives any idea of the vintage,..
Heads had been switched out on it, so if it's still the original configuration is anyone's guess,
But,
Check this out.

Had a 30mm Schadek oil pump in it,
But also, one of Jake's taller plungers with the angled groove -and- a shiny China pressure booster spring?


This might make sense, right?
If you put in a bigger pump,
You'll overwhelm the pressure relief and bypass the cooler otherwise, right?
Wonder if that was done intentionally by the man himself after careful deliberation and research?
Or was it some random dude who later rebuilt the thing?

Since the Schadek is smaller on the pump body OD,
I like to switch out the pump studs for bolts.
That way i can glue the pump in place and help stop leakage around the pump body.
As the case halves are joined, I'll 518 the bee hatch and smoosh it into place.
That'll stop leakage past the body, right?
Just gotta make sure to clean out the passages before it dries.

Because you aren't supposed to thread straight into the aluminum,
We insert the four pump studs, here using Keen-Serts.
Challenge is getting all of this flat, so the gasket gets good purchase, especially since we're not using one there.
Using shoulder bolts helps support and align things,
As well as helping seal there in the absence of sealing nuts.


All well and good, right?
That is, until the 30 pump goes back in.
Holes are NOT located accurately enough to clear the shoulder bolts we plan on using.
So now we have to find another pump. It took too much hogging to get the holes to work.


So, I immediately suspected my own work (of course),
But pulling a new 26 Schadek i got from Jake years ago and trying it on,
The holes lined up perfectly with no mods needed.
Same with a couple of covers i had.


So that got me to thinking...
I was always taught that bigger pumps were a hoax.'
My motors have all been smaller pump. Never a 30 ever anywhere.
Going to the type 4 store, all they sell now is the 30?
https://lnengineering.com/type-4-store/ ... ories.html

Now I'm starting to question all that i ever knew...
LN always only sold the good stuff.
Maybe LN just is over it and getting rid of old stock and out of type 4s like everyone else?

Check out the difference here:

30 on left, 26 in middle and 24 on right.
ALL type 4s, 914 2.0, Bus, anything... Always a 24mm pump, right??

The 26 is already a bit bigger.
Why always 30 for everyone?
Even Jake?

I dunno, man.. Going on the hunt for another pump, It's hard for me to buy a 30.
Have a few here because i always take them out.
A stroker Bus 2109, that might end up getting an oil cooler (against my advice)
Would you run a 30?
What are the chances the holes will be in the wrong place again?

If i had any more stock pumps in decent shape I'd use one of those with a stock spring.
If buying Brazil, it would be 26,
But now?

If anyone has anything to add, I'm all ears.

Thanks for listening to my rant.

The mystery is why Schadeck chooses to make the ACVW oil pump body the wrong freaking diameter, for decades.

I found that Schadeck pumps (back in the day at least, have not bought one in 20+ years now) had one "tight" stud hole, made them resist being inserted a bit almost like they were made to "feel" as if they were the right size, as the right size is an interference fit. Pulled the pump studs if multiple blocks as an experiment: Every Schadeck I had at the time (including a Berg hard anodized beast and one from Jake) literally fell in the hole on fully torqued blocks.

That's when I acquired and oringed a few Melling pumps... "known' to not work well and leak externally and internally... Iron pumps have expansion issues in an aluminum motor, but they wear like... iron. They fit no worse than Schadecks, even with the lack of expansion. I have 28mm versions. Have never seen issues from running a slightly oversize pump, but I gave up running 20W-50 Castrol a very long time ago as well... I also worked hard on getting the head venting fixed and did the lifter and rocker mods to get as much oil to the heads/valve springs etc as possible.

There is a US manufacturer of aluminum pumps for ACVW... Revmaster. They apparently fit right.
The main issue with them is they are specifically made for aircraft engine usage (or racing usage) motors with huge clearances, and those motors are effectively are oil cooled as much as air cooled, and AFAICT they only come in 38mm... I also recently saw pics of a race engine with a gerotor based VW oil pump of US origin.

Schadeck makes one ACVW oil pump that has a 24mm pressure gear stage that ---modded right--- won't leak pressure or suck air to the case--- the dry sump pump. It doesn't fit the case any better, but the inner stage is a 26 (or 28mm, cant recall) scavenge stage, and set up right the pressure stage output can be plugged, use a full flow cover for full flow plumbing output AND dedicated (and larger) oil inlet from the tank, works well as long as the oil return setup returns to the dry sump tank rather than the block. (pressure relief return mods inspired by Racer Chris's E-prod 914, were not as hard as it sounds). More complicated than most need tho. the pump body to case can be oringed just like any Schadeck..

I apologize for my rant as well, once had pics of all this stuff posted here, bitworm got them all eventually.

Jorge at EMW sells sleeved Shadeck pumps that are the correct OD . See if he has 26mm ones . I've often wondered how much market there is for a CNC'd pump body that takes the Shadeck gears/shaft etc .

Rant most welcome sir.

Would you run a 30,
Or search out a 26?

At least for a 2109 bus motor to be run by someone else..?

wreck wrote: ↑Sat Mar 29, 2025 5:28 pm Jorge at EMW sells sleeved Shadeck pumps that are the correct OD . See if he has 26mm ones . I've often wondered how much market there is for a CNC'd pump body that takes the Shadeck gears/shaft etc .

Hot tip.
We’ll try Jorge.

There is a CNC type4 style pump available. Made in germany i think. Given it is not cheap I assume it fits properly.

If I remember correctly. The pressure regulation of a type4 is a bit leaky, which is particularly annoying at lower rpms and may explain why rod bearings towards the flywheel end are the first to suffer. A 30mm pump may help compensate, if its run with modern 0w30 oil to prevent excess pressure at high rev & cold temps. That’s certainly the recipe i use on a type1 currently and will probably do the same on the future T4.

I would not hesitate to run a 30mm pump vs a 28 or 24, running the right oil..

The bigger pumps downsides are well (usually) understood and can be worked around.
In a perfect world you would convert to a real oil thermostat/external relief and ditch the factory setup except for overpressure.

On the Mellings I machined in "balance grooves' ala SBC racing pumps in pump body and cover, supposedly cuts down on pressure pulses and limits pressure hot or cold, which is an actual issue on those very tight cast iron pumps. (pressure pulses more of a timing variation issue if you have a timing chain AKA not ACVW)

I usually run 5w40 Rotella g6 or 5w40 m1 delvac1/TDT, although I have run 5w30 full synthetics from Pennzoil and QS (in the ACVWs) over the years to no ill effect and same oil pressure hot or cold...

The SAE xWxx viscosity ratings ratings oddly don't correlate terribly well with with many oils actual hot/cold cP thickness, which makes little sense but is apparently true. (some 0w30s are apparently thicker hot than some 10W40s and even 20W50s... GT.... some cheap ass 20W50s "performance oils" we all used to swear by are IIRC closer to 10W25 after a Kmile or so in an aircooled engine....)

Sometimes I can get the euro M1 0w40 and I buy a big box or jugs when available.
(The G6, Delvac or euro G4 all go in ~everything I own, and everything seems to last ~ages)

I may hit up EMW and see what they have re: sleeve pumps that actually fit per spec.
Seems like about as good as it gets. You could probably do same with a Melling to good effect.

Ran Mellings BITD like so many others.
Shocking to see how big they are now in hindsight.
Keep at least a small rowboat from getting away..

Pile,
Have a link to the mods you did al la SBC?
Never heard of any such thing.

Talked to Jorge today,
He does indeed sell OD sleeved Schadek pumps.
Never a 30...
Getting one soon.

Running Brad Penn now for years, and because a cam never went flat, we stayed right there.
The 10/30 or 10/40 variety would flicker the VDO dual sender attached oil pressure light, coming off the highway at idle after a hard run.
20/50 never did this. With a well-used stock pump.
Higher threshold of the dual sender - it never caused me concern.
And only on the hottest days and hardest running.

Do this for a "customer"? Probably not wise.
A big pump would give better readings on the gauge and never a flicker.
Oddly enough, this engine, while obviously low miles, had pretty chimped up rod and main bearings.
Purportedly always gave great gauge numbers...

Other things now come into play choosing a pump,
Not any of them fortunate.
Bearings are a crapshoot. Now hoarding old ones.

Other than that, it's buy what they're selling.
Silverline are steel-backed, and "KS" not. As of 2025.
They seem to have different numbers, but also between orders, or vintages/batches.
The KS seem to be better dimensionally.
Not sure steel backed really matters, especially for a bus. Other engines aren't.

We had one crank grinder locally here in the bay area, Ed's in Newark.
Past tense because the last crank they did was about a thou and a half over and the finish dreadful.
Would have been a feature on the too-big Silverlines we've seen of late with a bit of hand polish,
But just my luck the last batches were to spec and there went my oil clearance.

Another "crank guy", with only a polisher and balancer and now unfortunately also past tense,
He was able to polish away a thou and a half and correct Ed's messtake,
But now that his work ethic disappeared a moot point.

Without a source of quality bearings or a skilled crank grinder,
I'm going to have to find another hobby.
Supposedly there's still a guy in LA?
There are new Chinese cranks, but they have their own issues.

Unless someone out there wants to learn the ancient art of crank grinding,
I'm guessing bearings will continue to dry up that that'll be that.

Ah, it's been a good run, gentlemen.
Love you guys. *sniff*.

Here's the first hit I just got from the google, nice pictures.
The Mellings I have IIRC are 28mm.

https://www.corvette-restoration.com/20 ... balancing/