Metric Tap's Question/ Metric Bolts

[ein bora]

I want to run a tap through the holes in a aaz block, however I know nothing about metric tap sizes but there seems to be just a couple of different sizes. Can anyone please tell which one's I'll need to get in order to do them all.
Also - other than the head bolts (as I'll be using studs) which bolts should I be replacing during a re-build and if possible what are the sizes. I'm thinking crank and rod bolts?

Any help appreciated. Thanks

[burn_your_money]

M8X1.25 is probably the most commonly used size

[Vincent Waldon]

Common opinion is to *not* use a tap for this job, since it will remove metal and weaken the threads..you're after just the dirt. 

A different approach is to take one of your old head bolts and grind the end half-way flat... this will scoop up any dirt etc but leave all the metal behind.

[Vitwagen]

I cleaned the threads on my AAZ, but it depends on which bosses you want to clean.

Some are M8 x 1.25mm, others are M10 x 1.5mm. I used a bottoming tap to chase the threads - so long as you use a quality tap, it shouldn't remove any metal. The thread should only chase what was there already - I can't see how it would remove any extra? When I did mine, all I got out was the oily sludge that had taken up residence.



HTH

[theman53]

Make sure your tap is for 2b thread tolerance.
M6-1.0
M8-1.25
M10-1.5
M12-1.75
M14-2.0
That should do most of the entire car...I think the flywheel bolts are a -----at M7-1.0 and the axle stub is M16-1.5 But don't quote me on the last two.
The M6,8, and 10 should do most all of the block for you

[Vitwagen]

Do be careful though, as although all the ones in the block are as listed above, there are quite a few 'Metric fine pitch' nuts and bolts on VWs.

these are typically 10x1.25 and 12x1.25, so if it don't look 'right' it could be a fine pitch.