Putting the M20 back together - tips

[Andy348]

Great, thanks.

How should I go about cleaning shit off the top of the block? Use a razor blade? It's pretty gunky and needs a good cleaning. Should I clean the piston heads or cylinder walls?

[efficient]

you can use a sandstone the ones you use to sharpen your knives or a piece of sandpaper wrapped around a piece of wood. then just blow all the shit out with air.

[dougie30]

What has not been mentioned, and is important, is to use a thread chasing tap on the head bolt threads in the block. And then to blow out those with compressed air after a liberal dose of solvent.

Could you elaborate more about this? What exactly does it do?

[AndrewBird]

It cleans the threads out and returns them to their original size.

I will add that slightly chamfering the holes is a good idea too. Torquing the bolts down (previously) can pull the top thread up and leave it sticking above the top surface of the block. You want to get rid of this so the head sits flat.

[dougie30]

Thanks for the info