How do you tell if a used case is good?

Hi all

When I mentioned to a friend of mine I was about to buy a new case to
rebuild my engine, he mentioned that a friend of his had "a bunch of VW
parts in his garage". He was going to ask him if he was willing to part
with them.
Today I found out that he has a alledgedly good used case for sale and
that would save me real money to spend on heads and cylinders.

Besides making sure my bearing fit and there's no slop, what else
should I look for? My bug is a 75 regular FI, so would any case work
for me? I clearly can't check for cracks on the spot, can I?

Thanks for any suggestions.
Remco

A used case of unknown provenance but with no visible cracks or
internal gouges has a core value of $10 to $25 depending on age and
location, assuming it has all of its hardware (ie, nuts, bolts & studs)

To return a used case to service usually involves align-boring the main
bearing webs since the center-main pounds out into a four-lobed pattern
even in nominal passenger car use after about 50k miles of service.

All of the plugs sealing the oil galleries must be pulled and threaded
to accept replacement plugs. After any machine work, the galleries are
scrubbed clean and re-sealed.

A dye-penetrant test is performed on the critical areas (ie, base of #3
cylinder spigot bore, oil cooler ears, area adjacent to the threaded
boss provided for mounting the oil pressure switch).

Unfortunately, there is no known test that will detect a case that has
been subjected to heat-stress. Heat stress causes the magnesium alloy
to 'remember' its shape at the time it was raised to an elevated
temperature. Even though the thing mikes within spec at room temp it
will return to its heat-stressed dimensions when it reaches normal
operating temp. This problem alone is sufficient to rule out the use
of any crankcase of unknown provenance

-R.S.Hoover

> A used case of unknown provenance but with no visible cracks or
> internal gouges has a core value of $10 to $25 depending on age and
> location, assuming it has all of its hardware (ie, nuts, bolts & studs)
>
> To return a used case to service usually involves align-boring the main
> bearing webs since the center-main pounds out into a four-lobed pattern
> even in nominal passenger car use after about 50k miles of service.
>
> All of the plugs sealing the oil galleries must be pulled and threaded
> to accept replacement plugs. After any machine work, the galleries are
> scrubbed clean and re-sealed.
>
> A dye-penetrant test is performed on the critical areas (ie, base of #3
> cylinder spigot bore, oil cooler ears, area adjacent to the threaded
> boss provided for mounting the oil pressure switch).
>
> Unfortunately, there is no known test that will detect a case that has
> been subjected to heat-stress. Heat stress causes the magnesium alloy
> to 'remember' its shape at the time it was raised to an elevated
> temperature. Even though the thing mikes within spec at room temp it
> will return to its heat-stressed dimensions when it reaches normal
> operating temp. This problem alone is sufficient to rule out the use
> of any crankcase of unknown provenance
>
Thanks! What you said about heat stress was something that hadn't occured to
me.
This case is said to not be in need of line boring but, if it has been in
service, one has to wonder what happened to it that it no longer is part on
an engine, right?

I am convinced (reading through the threads and from what I've been told)
that line boring is not an option. The case I have now has bad saddle seats
and decided a while ago to not go that route.

I've been mulling over it over the last couple of days and will definitely
get a new case.
Now that US tax season of over, bug season started

Remco

> The case I have now has bad saddle seats
> and decided a while ago to not go that route.

Bearing saddles, that is

remco wrote:
>
> This case is said to not be in need of line boring but, if it has
been in
> service, one has to wonder what happened to it that it no longer is
part on
> an engine, right?
----------------------------------------------

I've found it best to take anything said about a part with a grain of
salt. Once you blueprint the part it's capable of speaking for itself.

------------------------------------------------

> I am convinced (reading through the threads and from what I've been
told)
> that line boring is not an option.

------------------------------------------------

Myth. When Volkswagen offered rebuilt engines (for about $300 ), all
were built on align-bored cases and offered the same warranty as an
engine assembled from all-new parts.

The bad rap for align-boring stems from the days when the memory
properties of the early alloy was not understood. The tricky bit here
is that the 'read' temperature of the memory-property was much lower
than the 'write' temperature. Once the case had been heat-stressed,
typically associated with a lubrication failure, the case would return
to its heat-stressed dimension even at normal operating temperatures.
That meant you could align-bore the thing back to spec (first
over-size) and the case would spin the same bearing as soon the saddle
saw enough heat to cause it to return to its distorted dimensions.

Changing the alloy (ie, adding more aluminum) altered the metal's
memory properties, meaning the later cases did not have that quirk but
the 'experts' had already decided that the fault was with the
align-boring. (The memory property was apparently related to trace
amounts of tin & neodymium present in magnesium extracted by the
Dowmettal process. Increasing the amount of aluminum altered the ratio
of those materials present in the alloy and 'turned off' the memory
property.)

Another aspect of the problem was the totally ****ty quality of the
align-bores produced by a very popular (ie, low-priced) portable align
boring tool. It was possible to produce an acceptable
METRIC-dimensioned align-bore with SOME of the portable tools but most
of the people who bought the things did so because they were NOT
machinists and bought the cheapest tool available, a low-quality
rip-off of the Porta-Line. In the hands of a competent machinist,
capable of accurately setting the cutter heights, the Porta-Line with
its heavier bar worked pretty well... assuming the cutters were
properly set. But the cheap copies with their whippy little bar were
incapable of cutting a true circle no matter how carefully they were
set-up. Bottom line is that a lot of shade-tree types produced a lot
of totally trashed engines... and provided further 'evidence' that
align-boring didn't work.

If you're a competent automotive machinist you can do an align-bore on
a VW crankcase using any 12" or larger lathe and the shops that
tooled-up for the task, such as RIMCO or Pauter, equaled or bettered
the factor spec. But it was rare for a shade-tree mechanic with his
dandy portable align-bore tool to even come close to the required
dimension, often because they insisted 1mm was equal to .040" when the
actual dimension is .3937"... and which they would blow-off by saying
forty-thou was close enough.

Close enough to ruin the crankcase, that is :-)

---------------------------------------------------
> I've been mulling over it over the last couple of days and will
definitely
> get a new case.
---------------------------------------------------

If you can afford it, it's always best to begin with a new crankcase.
Indeed, unless you've got a lot of VW engine-building experience the
wiser course is to go with a new crate engine from the Puebla plant.

A point never mentioned by all those wunnerful folks trying to sell you
stuff is that the maximum SUSTAINABLE output of the VW engine is about
45bhp. That's because MSO of an air cooled engine is determined by the
engine's ability to couple its waste heat to the atmosphere and all VW
engines use the SAME HEADS. (After-market heads are even worse, having
less fin-area than stock heads.) Bigger engine, the momentary PEAK
output can be just about anything but if you want to achieve the 2000
or so hours between overhauls that the engine is capable of delivering,
you have to accept its limitations. Build the thing for maximum
output, your Mean Time Before Overhaul (MTBO) can be as little as ONE
MINUTE... which is acceptable to some although a vast mystery to the
technologically naive majority. (It has to do with the metallurgy of
cast aluminum [ie, of your heads].)

-Bob Hoover

Wow - thanks for that lesson, Bob! I am always interested in details
and background.
I could not find any local shop that had dealt with line boring VWs.
Some used to do it, others said they could probably do it but didn't
get a fuzzy feeling on any of them. I do have access to a tool room but
don't want to tackle that one.

Since I am new to bugs, I figured it was best to start with a solid
basis so will get a new case, heads and cylinders. I am not new to cars
nor to tools and am used to reading and following specs, so the
rebuilding doesn't scare me. For me, buying a crated almost turnkey
engine would only be half the fun -- not that there's anything wrong
with that, but that is not what I want to do.

I was lucky enough to get some NOS FI German heads and will get a case
sometime this week.

About cylinders, there are a lot of choices. Aircooled.net has some
NOS, NS and I also see a lot of places selling the cylinders
manufactured by Mahle.
Again, I am not looking to build a street rod nor anything high
performance, so would any of those be adequate for my application?

Thanks!
Remco

Remco wrote:
>
> Wow - thanks for that lesson, Bob! I am always interested in details
> and background.
> I could not find any local shop that had dealt with line boring VWs.
> Some used to do it, others said they could probably do it but didn't
> get a fuzzy feeling on any of them. I do have access to a tool room but
> don't want to tackle that one.
>
> Since I am new to bugs, I figured it was best to start with a solid
> basis so will get a new case, heads and cylinders. I am not new to cars
> nor to tools and am used to reading and following specs, so the
> rebuilding doesn't scare me. For me, buying a crated almost turnkey
> engine would only be half the fun -- not that there's anything wrong
> with that, but that is not what I want to do.
>
> I was lucky enough to get some NOS FI German heads and will get a case
> sometime this week.
>
> About cylinders, there are a lot of choices. Aircooled.net has some
> NOS, NS and I also see a lot of places selling the cylinders
> manufactured by Mahle.
> Again, I am not looking to build a street rod nor anything high
> performance, so would any of those be adequate for my application?
>
> Thanks!
> Remco



Go with Mahle. If you want a step better, get the Mahle Forged kit.
Otherwise the same but better quality pistons.
Not necessary for a stock engine but I'm just letting you know

Cofap used to make them too, with inferior rings and not quite as good
pistons.

Jan

Jan Andersson wrote:
> Remco wrote:

> >
> > About cylinders, there are a lot of choices. Aircooled.net has some
> > NOS, NS and I also see a lot of places selling the cylinders
> > manufactured by Mahle.
> > Again, I am not looking to build a street rod nor anything high
> > performance, so would any of those be adequate for my application?
> >
> > Thanks!
> > Remco
>
>
>
> Go with Mahle. If you want a step better, get the Mahle Forged kit.
> Otherwise the same but better quality pistons.
> Not necessary for a stock engine but I'm just letting you know
>
> Cofap used to make them too, with inferior rings and not quite as
good
> pistons.
>
> Jan

So I need to get a new set of rings for my Cofap P/C's? What makes
them inferior? Not a big deal to get a new set.

Jan Andersson wrote:
> Remco wrote:

> >
> > About cylinders, there are a lot of choices. Aircooled.net has some
> > NOS, NS and I also see a lot of places selling the cylinders
> > manufactured by Mahle.
> > Again, I am not looking to build a street rod nor anything high
> > performance, so would any of those be adequate for my application?
> >
> > Thanks!
> > Remco
>
>
>
> Go with Mahle. If you want a step better, get the Mahle Forged kit.
> Otherwise the same but better quality pistons.
> Not necessary for a stock engine but I'm just letting you know
>
> Cofap used to make them too, with inferior rings and not quite as
good
> pistons.
>
> Jan

So I need to get a new set of rings for my Cofap P/C's? What makes
them inferior? Not a big deal to get a new set.

TerryB wrote:
>
> Jan Andersson wrote:
> > Remco wrote:
>
> > >
> > > About cylinders, there are a lot of choices. Aircooled.net has some
> > > NOS, NS and I also see a lot of places selling the cylinders
> > > manufactured by Mahle.
> > > Again, I am not looking to build a street rod nor anything high
> > > performance, so would any of those be adequate for my application?
> > >
> > > Thanks!
> > > Remco
> >
> >
> >
> > Go with Mahle. If you want a step better, get the Mahle Forged kit.
> > Otherwise the same but better quality pistons.
> > Not necessary for a stock engine but I'm just letting you know
> >
> > Cofap used to make them too, with inferior rings and not quite as
> good
> > pistons.
> >
> > Jan
>
> So I need to get a new set of rings for my Cofap P/C's? What makes
> them inferior? Not a big deal to get a new set.

I hear they wear out exceptionally fast, that's all. It was a psoblem 10
years ago, don't know if it still is.
I use only Mahle.

Jan