Backfire under loads

[geezer#99]

Originally Posted by liftlawssuck

So a little update. I added a ton more initial timing. It's close to 30* now and runs much better. Not great but WAY better. Doesn't backfire under load. !!

That kind of timing tells you that your balancer/timing tab is really inaccurate or you’re reading your timing in the wrong spot on your 305.
A 305 should have a timing tube at the 12 o’clock position that you sight down to the balancer. Right behind the water pump.
Are you timing it with this or is there a timing tab at the 2 o’clock position?

Some info here.
https://www.crankshaftcoalition.com/..._TDC_Lines_SBC