nawbie here thanks for having me.

[michael1]

have a problem with my 390 b\s to 428,holley 750 mild cam,breakerless dist.cannot seem to get timing right i get a intake backfire at low rpm on a pull.if i retard timing to about 20 btdc loose backfire but engine runs rough no power at all anywhere i set timing.hope someone has a idea
thanks.

[blykins]

Did you assemble the engine?

Sure the distributor is in correctly? Maybe a tooth off?

[BossCER]

Maybe double check your firing order (no crossed plug wires?)

[redmt]

Check your timing all in at whatever rpm you hit max advance and then at idle. Sounds maybe like the distributor advance is either hung or not enough to start with. Depending on a lot of factors, you should be at about 34-38 all in and about 6-8 at idle. Then again ,,,,,,,,,,,,,,,,, it could be any one of another issues. Who built the motor and is this a new problem or just developed?

[Barry_R]

Could be a tooth off on the timing set.

[michael1]

thanks guys for all your advice,and sorry it took me so long to get back. i had the motor done at a shop here in pa.only 20 miles off dyno.i think i found the problem.seems like all my hyd lifters cannot properly preload builder installed .551 lift cam with stock nonajustable shaft rockers.one bent pushrod and lifters that all seem to be dry.funny can't get builder to call back? thanks any advice on rockers would be helpful.