Rebuilt 460 popping/ backfiring when reved past2k or under load
 

Got a 1979 Ford 150 with a mild built 460. Starts right up sounds great but try to rev it past 1800 - 2000 rpm it pops / back fires , sounds like one or two cylinders doing it. Take it for a drive it gets alot worst the more load. Truck has msd 6 box , blaster coil, msd cap rotor and wires on new reman distributor, auto lite 45 plugs. All brand new parts base timing is set at 14° btdc , and seems to be advancing fine. Have tried adjusting timing both ways with no change in popping. Carb is a basic Holley 750 4160 manual choke. Just cleaned it , every thing seemed open and threw a new power valve in for fun. Has a steady 7 psi just before carb. It's been a long week hope some one can give me some ideas , will be grateful thanks!!!!

Might be lean. Make sure you're getting a good firm shot out of both squirt nozzles. Might do a compression check to rule out valve train probs... bent push rod, stuck valve etc. Good luck with it.

Just had in running in complete dark ness and its arcing at the end of plug wires at plugs on all cylinders ! Any ideas!? Plug wires are new msd!

Wow... that's no good... are you sure the wires are snapped on the end of the plug? Some times it's hard to tell if the wires are on all the way or not. Brand new wires you sure wouldn't think the insulation was bad. For sure not on all of them. Sorry I haven't got anything else. Come back and let us know how it's going.

New caps are very difficult to get all the way seated on new plugs. I always put a little dab of clear dielectric grease on the end of the plugs before installing.
The caps are most likely your issue, but I would also make sure you are not running too lean. A wideband AFR gauge is always a good idea with mods like yours.

Sent from my iPad using IB AutoGroup

Also sounds like wires might be crossed. re-check firing order and routing of wires. If that checks out OK, check the rotor phasing.

If you have a smog pump installed, that might be the problem... especially if you have headers. I rebuilt a 351M, and when I would accelerate, it sounded great, but when I remove my foot from the gas, I would get the popping similar to what you're hearing. Try removing the belt to the smog pump, see how it sounds.

Well knowing you are getting arc at the plug boots srart there first. New wires are a tighter fit and require some pressure to seat. If it still does this go to your msd box and see if your rpm limiter is set too low. Via plug in limiter module or if it has the rpm adjuster knob. I had a buddy who thought it be funny to play around with mine one day and dropped me down to a max limit of 2500 rpm. We had a little laugh after I found it, then I bitch slapped him

If your plugs are gapped too wide this can also cause the spark to find an easier path to ground.

^^ yep that's what I was thinking. Double check your firing order then pull all the boots off and put a little di-electric grease on the wires ends and reinstall. Make sure they are seated all the way on with a click.