Krazy, I thinks you got your keys mixed up.:wink:
I think you meant to say; Backfires through exhaust= ignition timing is too retarded.
Backfires through intake= too far advanced ignition timing.
To the Op: Non adjustable factory rockers doesn't necessarily mean the valves can't be too tight. I would still recommend you verify they are good. Especially if there was a valve job done or pushrods & lifters replaced.
