Backfires

[winfield scott]

What kind of dizzy HEI ? I had a similar problem and ended up being the pick up coil in the HEI. I borrowed another from a friend and Wala !
If you have another dizzy, throw it in and try it.
Just a thought!

[mike wade]

What kind of dizzy HEI ? I had a similar problem and ended up being the pick up coil in the HEI. I borrowed another from a friend and Wala !
If you have another dizzy, throw it in and try it.
Just a thought!

That was in Carson City I remember that now........

[Indycars]

I assembled this engine and had it running smoothly at 2000 rpm for 20 mins or
so to break in the cam as required about 6 months ago.

After more thought, that break-in is suspect. It ran fine then, and now it don't. Do a
visual inspection of the valve lift with the engine running or on the starter. If it's bad
enough you can see the difference in lift between valves. Drain some oil and inspect
for metal. Cut the oil filter open and inspect.

[dwleo]

relashing today

[dwleo]

I assembled this engine and had it running smoothly at 2000 rpm for 20 mins or so . . . . I regapped the plugs (disgustingly fuel dirty with soot) to .040 and rechecked the vacuum lines.

This tells me two things: I believe the backfiring is caused by an overly rich mixture (dirty plugs show this) allowing fuel to 'puddle' in the plenum after a few seconds and causing the backfiring. Also, I believe you may have blown the power valve in one of the backfires, and this would contribute to the fuel mixture problem. Just my 2 cents!

Spanky, I am leaning more and more into your hypothesis about the power valve. It is fuel rich to a point of flooding out or a combination of that and a bad lash.
Lash today then taking off the carb as the next step.

[dwleo]

All is completed. Combination of lash, uh, adjustment of valves, TDC error, and timing. One would play off the other and my warped brain couldn't follow the logic trail completely enough./

Many thanks to tinkirk (H.A.M.B.) who reached out with a tel number; I called, we talked and end result is the beast fires immediately and is fairly smooth.

Thanks to all for help and especially to tinkirk.

[Bill Cleveland]

Way to go, Daryl! Ain't this a great hobby, and the people who follow it are the best - always quick to lend a hand! Glad it's solved, and you can move on to other challenges. Keep us posted . . .