Strange Idle Issue
I'm experiencing a strange idle issue when hot, and I am hoping for some ideas on what to check next. '69 Z/28 with original non-matching numbers 302. Motor was recently rebuilt and runs strong. Jerry just red-did my Z/28 intake (looks beautiful), with DZ Holley carb; brand new reproduction (original is in a box getting ready to go to Jerry. Idle's fine when cold. When the motor gets warm, I have an idle dither at stops, and will stall without goosing the gas.
Weird; I took her for a drive up the highway last Saturday morning with my daughter. Drove 20 or so miles to a gas station that sells 110 racing fuel, picked-up 5 gallons and drove back. Ran great - coming off the off-ramp, i put her in neutral and let her idle for 1,000 feet or so as i rolled to the exit; idled dead-nuts fine at 1,000 rpm. Came to the stop light and she started to dither... Also; never fails, she dithers as i pull into my driveway every time... I've checked floats and idle screws, timing is good and she runs well otherwise.
Also of note; i'm running pertronix distributor, but it's at least 10 years old with low miles. Brand new plug wires and plugs. I'm thinking maybe i need to replace the coil?
Any ideas on what to dig into next would be great. Thanks for your help!
Finally, I'd love to post some photos. i use ios iphone and can't seem to figure out how to make them smaller so i can post here.
'69 RS Z/28
Glacier Blue with Black Stripes
Non-matching numbers 302
M22 4 Speed
4.11 rear end