GMC 305 v6 Holley 500 swap woes

[AngryPirate]

For those on the gmcclub, this is a repeat post...

So, I got a factory refurb Holley 500 2bbl 4412S wallered out the opening a bit to match the opening on the bottom of the new Holley carb adapter plate, torqued everything to spec, hooked up the fuel, throttle linkage, choke and vacuum advance to the dist.

It runs like ****, when I can even get it running. When it does run, the vacuum advance runs the RPMs up super high. I adjust the dist to lower the rpm but it seems to be slightly misfiring. All other vacuum ports are plugged.

I've tried everything... setting the idle mixture screws out 1 1/2 turns from turned in all the way, messed with the ignition timing and I think I smoked my coil (and I'm sure my starter is about to go too).

It ran decently with the Stromburg WW2 carburator.

This is MADDENING.

Any other ideas?

The only other thing I can think of is the timing chain skipped at some point? It there an easy way to determine the initial timing of correct?


Side question: with the new carb, how does anyone access the #3 spark plug to change it or seat the boot easily?

Thanks for any help.