Hey, i got an 81 with a 347 and this thing has a heavy backfire now. heres what happened. i was installing a tee in the intake manifold to hook up the new water temp sensor in the old heater loop and had to pull the distributer out to get it in. reinstalled the distributer and now everytime i turn it over it backfires terribly. i understand its timing but i just cant seem to get it right... any ideas?