ran way lean....either timing, fuel curve, or bad injectors...

Not sure about a MEFI 1, but a MEFI 3 will pull a predeterminded amount of timing out when the ECM can't detect the knock sensors (disconnected or connected improperly). It depends on the tune how much gets pulled. You could have retarded your timing a bunch by disconnecting the knock and shot your EGT's through the roof!

God I Love carb's for engines like these.

Sorry, I know, that's no help.

Agree that the problem is running lean with no spark retard. When I talked with Tyler Crockett he said that 36 psi was probably too low but was a good place to start tuning. The problem was most likely detonation but the question is why did only the # 6 piston melt on each engine and why did the center electrode of the spark plugs melt only on the # 3 cylinders?

The Rinda software was reading 0 spark retard with the knock sensors disconnected so I am not sure the MEFI 1 has the same strategy as the MEFI 3?

Carbs, Intakes and and MSD Distributors and looking pretty good about now...

the MEFI 1,2,3 all use the same algorithm to retard timing. The observed variables are RPM, Knock Detection, IAT, MAP, ECT. MEFI 4 expands the spark retard by adding 4 additional variable. Then each computer has its own knock recovery table.

I have seen your described failure and it was attributed to detonation caused by either to little timing or to much timing. The heads you use have a great deal to do with timing tables. I am guessing you are still using the 088 heads. They have a pretty narrow ban.

You can use your current distributors with carburetors. When not controlled by a computer, the modules give a 22* advance all in by 2800 rpm. I've used them with carbs a few times.

Just in case that helps.

Sorry for the carb talk.