Van Once Ran

1977 Sportsman wagon, Mopar 360 LA
rebuilt motor same carb as old motor. It
backfires and pops through carb. It will
not run past idle. When throttle moved it
just takes “breaths”. 1˝ to 6-inch vacuum
on motor w/ no hours on it rebuilt from
machine shop. The motor before it had
wiped cam and bad exhaust valve tip/tight
crank clearances w/rod knock. Cause was
no zinc additive in oil. That motor ran only
for 5,000 miles. This motor same Holley
4 Bbl carb, new 8 months ago. No it is
not distributor, vacuum leak, intake leak,
brake booster, PCV valve, and not wires in
wrong firing order. Timing is spot on.

Best guess: Cam timing is likely a tooth or
two off.