Do not underestimate how tough these engines are. if your broke, pull the head, have a look, fix the valve if that,s all it is, using some used bits from your other head. Slap that head back on, I have even reused a head gasket when in need, some of the B18/B20 engines I have pulled apart have had a very nice copper and cardboard(?) gasket that did not stick to the head or block during dismantling and was easy to re-use. to all the naysayers on this I know this is not recommended but it has worked for me, besides go to mexico and watch some mechanics there, you would be amazed. Anyhow, my engine before I rebuilt it was still pulling nicely, when I opened it up there were a few nicks etc on the cyl walls, and the valaves had definatly seen better days. One of the things i love about my 120 is that it is not a precision machine, and therin lies it's strength.
Patrick of Mtl '68 220, '83 245, '92 VW Eurovan (I need it for work)