MJAMGB--read all the posts on rebuilding the B-20 and have a problem that I hope you might be able to answer. I have a 1973 145 wagon that had the low compression F head in it. Wanting to upgrade, I installed an F head that had been milled down to E head specs. I'm not very knowledgeable on rebuilding, and never knew, until I read your post, that the surface of the head had been hardened. Sometime after I installed the "E" head, I began to experience an erratic idle (this car has the D-Jetronic system on it, not carburetor). At cold start up the car would idle at around 1000, as it should, then cut back to 750 as it should, but then sometime soon thereafter, the idle would suddenly drop to around 150, barely able to sustain itself. Go into a store, shop around a bit, come back out, start it, idle would be back up to 750. But a few minutes later it might drop back down to 150. And so it would go. I tore my hair on that injection system, replacing absolutely everything, from the pressure regulator to the temp sensor, but nothing ever cured that erratic idle. The shop that did the milling on the head ripped me off, putting in valves they said would handle unleaded gas (they didn't, they seized, but fortunately came unstuck and thereafter I added a lead additive), milled out a divider between the intake and exhaust valves, saying it would up the horsepower, etc. I'm thinking of restoring this car back to specs, but I would like to know if the milled head and the erratic idle are connected someway, i.e. warping or whatever. Any possible explanations from anybody on this post would be most welcome. Dick