Measuring case bore
 

Hi everyone,

I had my engine (2.4 MFI) mostly appart to repair a tiny leak in the oil cooler, and noticed a bit of vertical play in the crankshaft (0.060) while examining the real seal at the flywheel. Since everything was already half appart, I decided to double check the crankshaft clearances and make sure all was ok.

Something has me stumped, though: when I measure the bearings and add the thickness of the bearing, I get to exactly 62.000 - 62.012 perpendicular to the parting line. At 120° (ie at 11 - 5 o'clock), I get something a little larger (62. 070), but not at 60° (1 - 7 o'clock).

So, I tried to check the bore without the bearings, but it comes in too small in most places (-0.030) and too large in one direction (out of round). It seems that torquing the case without the bore causes the case to deform a little more. So my question is how are the bore diameters measured accurately without the bearings? Should I not torque down to spec (I falways ollow Wayne's book on the torquing procedure)? I did not have n°8 installed since I needed the access.

Thanks for any help!

Not having #8 installed will be the main error.

At the flywheel end, you have 2 dowels to align the case. At the pulley end, the #8 bearing acts as the dowel. Without the #8 bearing installed, you cannot use any of the measurements you took.

Install the #8 without the pin, and gently torque the case... if you don't torque the pulley end too much, you should be able to tap out the #8 bearing. Then torque the case to factory spec. Don't forget to install the 2 nuts at the pulley end on either side of the #8 bore.

Use thread lube on all through bolts before torquing.

Now you can recheck your tunnel clearances.

Wow, the answer came from all the way down under, what a great forum!

Thanks, will follow this and report back. In the meantime, I will start looking for a competent machine shop just in case.

You need the #8 bearing for accurate measurement. I believe there is a aircoold VW bearing that is the same external dimension as Porsche bearing but with larger center bore so you can get bore gauge in to measure.

john

Thank you all for your helpful replies. I removed the dole pin from #8 and pushed out the bearing once the case was half-torqued. With this, the numbers were much more reasonable, with what appears to be a tendency for closing in of the bore. Thus, the case is now with the machine shop for a bore alignement to ensure that everything is up to spec. Fingers crossed that there is not too much oval deformation.


Case Bore (measured)
1A 61.954
1B 61.935
2 61.980
3 61.946
4 61.933
5 61.955
6 61.957
7 61.942