How do you tell if a used case is good?

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

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

Bearing saddles, that is :)

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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.

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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 shitty 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 :-)

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definitely

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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

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.

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