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I've got a '69 DZ 302 with a 780 Holley. With the current carb settings, it will idle at 950rpm about 3-5 minutes after start up. After I begin driving (another 5-10 minutes), the idle the creep up to about 1,100rpm. It will generally stay around 1,100rpm unless I drive it a long distance. If I drive the car 45 minutes to an hour, the idle will go up to the 1,300rpm range. How do I get the idle to settle down to around 950rpm even after the motor is fully hot without sacrificing start up idle too much? The car doesn't have a choke or exhaust cross-over from the heads.

Here are some details on my combo to help diagnosis: DZ 302 with 11:1 compression, 780 Holley 4053DZ, 247/254 duration @.050, Edelbrock Performer RPM heads, stock intake, 1 3/4 headers, 110 octane race gas.

Thanks.
 

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Welcome to the club. I hope you find it enjoyable.

No choke and probably no choke linkage either, not a problem. Your supplying more than enough fuel for cold, but as engine warms up, needs less fuel to run.

First item I would check is to see and make certain throttle returns to the same spot every time pedal is released. Fix it if not.

Let engine idle for hot temperature and set where you want it. Don't worry about cold idle yet.

Now, it won't idle when cold. Good cheap fix is to acquire the A/C solenoid and bracket and attach to throttle plate, probably already has the two bolt holes at driver front side. Attach solenoid here, electrical hook-up to 12 volts on ignition, and ground and a switch. Energize solenoid, adjust hex bolt out to open throttle plates for desired Cold rpm. When engine warm, turn off solenoid.

Back to warm curb idle.

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Everett 68/350/PG/11.90/115mph

[This message has been edited by Everett#2390 (edited 04-01-2002).]
 

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Mine does the same thing, I have been blaming it on the plugs, I use 44t A/C Delco. it didn't do it with 45ts'wich is a hotter plug, I think my problem is a combination of being a little rich and to cold of plug.
 
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