hello all
HELP , classic rangy 4.2 , intermittant firing into exhaust and inlet manifold . this is my fault as I let the lpg level get to low . big back fire and blew the intake pipe off , repaired this reattached the small pipe on rear of plenum . this misfire there on petrol or gas . I can't pin down the problem , and one with any ideas . always starts fine and seems to not have so much of a mis fire at a constant engine speed !

No i'm afraid it's probably fooked, your best course of action would be to sell it to me for scrap value have you checked the afm is working fine? they can get damaged with backfires. other than that not too sure, running with a low lpg level shouldn't damage much unless it was running so lean that you burnt out a valve? have you done a compression test on all cylinders? check all your basic settings, ignition timing etc as you shouldn't get a backfire from running on low fuel level so probably another reason for the big bang

i have a known good pre tuned 3am afm if your interested pm me