<VV> Question on Hot Knocking

[Todd Miller]

OK folks, looking for some advice and group problem solving.
 I have my 69 Monza Convertible, 110hp, 4-speed, that I am fixing a few things up on and driving a bit more to insure reliability as my son is wanting to use the car in his wedding next weekend. This is a great running 110, several Corvair mechanics and knowledgeable folks have commented on how great it runs, how smooth it is, and how good it sounds.  We rebuilt the engine about 10 years or so ago after having broken a piston ring.   So, the car runs great, especially when it is cold.  It also runs great when it is hot, after driving for some distance, however, when hot, as I take off from a standing stop, I get a couple of quick knock sounds from the engine until I get the revs up.  When hot, it still runs great, and great in every gear, without knocks, except for taking off from a standing stop.  If I really rev it up more, and slip the clutch a bit for a spirited drive-away, it does not knock. So, I am wondering, what is causing the knock?  Could it be that the timing is advanced too far?  I don't think this is the issue as it runs great before it gets hot, but not sure.  What else could it be?  I use 91 octane non-ethanol when I can, and 93 octane ethanol when I have to.   Thanks for any ideas. Todd in Texas69 Monza Convertible #338865 Corsa Turbo Convertible