Z-28 Won't Start

Greetings,

I am an experienced mechanic and have never been stumped on non-fuel injected engines. I'm not a Chevy-guy so bare with me please. I have a good one here that I think you will be able to help me with.

Here's the story. My neighbor has a 1985 Z-28 that has a crate 350 HP engine in it with a Demon 725 cfm 4-brrl carb. He started having trouble with it last fall when it started getting cold. Probably the choke. After he fiddled with it most of the winter he asked me to look at it because he couldn't get it to run well at all. A few days ago I worked on it. The first thing I noticed was that it has an electric choke and it had no electrical connections. Next, the choke was twisted way rich. Then I saw that the spark plug wires were on wrong - they were one post counter clockwise. This is not too big of a deal if the distributor was turned to compensate for this. I think the biggest problem was the choke. It's lack of connections and rich position resulted in it running very rich, loading up and stalling out. I spent a couple hours and went over everything. I repositioned the distributor and wires, tweaked the choke, added the necessary circuit for the choke coil, gapped the plugs, checked the spark, et cetera. Soon I had it running very well. I set the timing for about 10 BTDC and off he drove. Completely content that he had his Z-28 running again.

He came over tonight because it would not start. I checked spark, fuel, air all seemed well though the spark was not purple... it was sort of bright orange. I temporarily jumpered the battery plus (+) terminal directly to the +B on the intergral coil-distributor cap to no avail. It will not start. It almost does, but won't. I rechecked the timing while it cranks... it was still where I set it. I have tried ether too... nothing, nada.

I have checked everything I know to check on it. It is getting fuel, spark, and air, but simply will not start. I have checked for vacuum leaks - can't find any. The battery is good and cranks it over very well. As it does so it almost starts, cranks a few revs, almost starts, cranks a few revs... et cetera.

My next guess is that now that everything is set right and the engine is cold that cool spark is giving him trouble. Do you recommend changing the capacitor in the distributor, the integral coil/distributor cap, both, or something else? Do you have advice on something else to check first? Please advise.

PCitizen.

Do you recommend changing the capacitor in the distributor, the integral coil/distributor cap, both, or something else? Do you have advice on something else to check first? Please advise.

PCitizen.
There is no capacitor in the HEI distributor, the large silver thing is a condensor, used for a tach filter. If he has weak spark I'd check the coil, and if that checks good, the ignition module (sits under the rotor).

Agreed... It's called condensor. You're right. That's what they're called on my older cars too. Momentary laps of memory.

I will check the coil and ignition module instead.

PCitizen.

ive had the same problem twice.. once was the ignition module, and once was the coil..
both times fuel, spark and air were present..

hope this helps
good luck

Thanks. I will check it out soon. BTW: Nice car!