My timing was off, and I reset it, trying a few variations until I settled on advance of about 13. I also tweaked the carb at the same time.

BUT now it's dropping in power when I punch the pedal hard. It staggers off/on power about twice a second, shuddering strongly until I let the pedal up again.

- I have an Edelbrock Thunder series carb.
- Only happens on initial punch of the pedal; anything gradual is fine, and if I'm already rolling strong, it doesn't seem to happen.
- I don't have vacuum advance hooked up. It was this way and fine when I got the car, and everytime I hooked it up - it seemed to do nothing or actually have a little slower acceleration. Connected to timed advance was worse, manifold advance was a little better. But none is fine...
- Could be related to a vacuum leak - I hear a whistle when rolling sometimes, but I haven't found anything, as it goes when idle.

Thanks in advance. (I saw the thread similar to this, but was different enough to add my own, as his was definitely timing).

What is your total timing?

Dave

I have to check the specs on the distr. It's got a Hypertech cap and rotor kit, but I can find no information on these...

Don't worry about specs, you need to check it with a timing light so you know what you really, (initial and total) and when total is in by. You said you settled on advance of 13, I'm guessing you meant 13 degrees initial timing. Try about 16 if you have any kind of performance cam in there, then find the total. Get the idle as low as possible, like 600 rpm, when setting the initial so that the advance isn't coming into play.

Put the carb back the way it was until you get the timing situated, then changes to the carb.

just curious, but if you have a vacuum advance, make sure you plug it when doing your timing.

Thanks for the help so far -

I always have vacuum advance disconnected (and all ports plugged) whenever doing timing.

Yes - timing light shows right between 12 and 14. I had it more advanced (close to 16 or 18) for a bit, but had issues with it starting and running smoothly.

As it advances beyond idle, I have no idea how to read the advanced settings as the mark moves so far PAST the marked scale (which only shows to 14 degrees).

Also - We are not sure what cam is in it, we can tell it's slightly "hot" but not much. Almost certainly not stock. (Any way to tell without pulling it?)

I don't have a tach on this (yet... just Malibu gauges) so advanced rpms are hard to tell...

Did I miss a part where you said what engine you are running?

A digital type timing light with built in tach (like this one on eBay item # 260248758812) will tell you what your timing curve looks like. Or you could borrow one.

It's a SB 350. Nothing special, mostly original.

I will look into the tach/timing light today.

Great Brian, the engine type helps.
BTW - I just got one of those timing lights off eBay for $80. Summit sells them for $199.

Problem solved, but unrelated to timing (although I think rotating the distrib caused it)...

With closer look at the distributor cap, one of the wires had corroded (engine heat) and had not been firing, or maybe not consistently. Also explains the rougher idling that had been happening...

Thanks again for the help. Will certainly invest in the better timing light though.
BTW Herb, that car is a stunner!