Crank Wear VW

From: <[email protected]>

To: <[email protected]>

Subject: Re: Crank wear

Date: Sunday, October 22, 2000 4:39 PM

In a message dated 10/22/2000 5:57:45 PM Central Daylight Time,

[email protected] writes:

<< things like very dirty oil, and oil starvation, can score the journals

of a crank, which means it has to be turned... while you should change the

p/c's on every rebuild, you may be able to get away with just miking the

crank journals and having it checked for overall straightness... the latter

requires a jig, or some method of rotating the crank with a mic against the


it a race situation, you would also have the crank checked for cracks >>

Crank wear ????? Its very easy to spot using a 2-3 inch

micrometer.....You will begin by cleaning the crank, then placing into a

holding fixture perhaps a vise or stand it up on the flywheel where the crank

dowel pins engage to it.....2.1564 is standard ,and the wear limits as well

as tolerance for new parts can be found in your Bentley manual.......You will

check the diameter of both main and rod journals twice , the second reading

will be 90 degrees from the first measurement.....This will let you know

right away about a journal thats out of round.....You will find the maximum

wear at or near the oil holes on cross drilled cranks......You will also find

the maximum wear occurs at the center main because of the flexing problems

inherent to the VW crankshaft......For this same reason its not a good idea

to use more than a .010 undersize crank ......The people selling and

endorsing .020 cranks and beyond are either ignorant or dishonest or

both.......A final inspection at home will be to check for out of round or

bent at the center main......V blocks as pictured in Bentley allow you to

rotate the crank while using a dial indicator, again check Bentley for the

spec.......Finally you should visit the machine shop and get it magnafluxed

to check for cracks.......Magaflux simply uses increasing A/C current to

magnetize ferrous parts and then a liquid containing metallic particles is

poured over the part.......If a surface crack exists the particles will line

up and give a visual indication as a black light is passed over the part

,decreasing A/C current is used to demagnetize the part after checking ,

make sure they di this as you don't want a magnetic crankshaft.......If a

crack is not on the surface, or a inclusion exsists X-ray is the preferred

method for detection.......Lucky for us VW cranks don't crack all that often

.....Something else you can do at home is to grip the crank in one hand near

the end (either side) and strike one of the cheeks with a wrench.....Don't

get carried away, just a good tap and it should ring meaning no big

cracks.......Usually for what a machine shop charges to freshen up a crank

you can purchase a nice 10/10 ready to use from one of the reputable

suppliers.......I don't see to many good standard cranks any more, but who

knows you may get lucky.....Good luck


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