I have been dealing with a timing issue in my 70 f-100 that has a 351w in it. The motor is completely rebuilt. It has no vac leaks. I swithed the electronic distributor over to a points disty with a pertronix system in it. I have checked the timing to many times to mention. When I step on it to really get it, it bogs down. until it reaches about 2500 rpm's then you can feel it catching up. I was wondering if the wobble I see in my harmonic balancer is because the ring on it has slipped? This is really the only thing I can think of. I know I got my dots lined up on the timing gears and I dont have any vac leaks. Sound like harmonic balancer too you?????????

 

To check your harmonic balancer, put #1 cylinder at TDC by checking the piston travel, check and see if the timming mark for TDC on your harmonic balancer is in line with the pointer. If not, the ring has slipped, your timing is off and you need a new balancer. Or .......

The seat of the pants racing timing is as follows: set the timing with the light and by the book (just to get it close) then advance the timing in small increments, test drive it and accelerate sharply. Do this until you hear the valves rattle under acceleration, then back off the timing a little, this will give you max performance.
What you described sounds like a fuel issue, if it cranks O.K. and runs O.K. except when you put you foot in it, you probably have too large of jets in the carb. and when you step on it, it is trying to drown the engine until the RPM's come up and it can burn the larger amount of fuel. check your jet size and try dropping down 2 to 3 sizes.

 

I have advanced the timing as you described and my acceleration improved but the valve/lifter noise drove me nuts so I backed back down at time. When in time it spits back through the carb when I shut it off and if I cant get it to fire up at first try in the morning I have to crank on it for minute. The carb is a 600 edelbrock with performer intake. I did no mods to the carb just put it on. So could it still possibly be too much gas? I will check the balancer. Thanks for your help.

 

The 600 cfm carb on an unmodified 351W is probably a little too much for just a daily driver. I would drop 4 jet sizes and try that. Also the hard starting and backfire suggest that the timing is a little to far advanced, try backing off about 4 degrees. If it is still hard to crank back off 2 degrees at a time until it starts normal.

 

as a side note if you can see the balancer wobble
then it is BAD
get a new one ASAP
a bad balancer can and will cause the crank to twist apart