Carb tuning on 383 big block

Reece Stephens

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Somebody HELP ME. I have a 383 2 barrel, I recently converted to a 4 barrel, I have a freshly rebuilt edelbrock 1406, it's a 600 cfm 4 barrel with electric choke, I have everything hooked up properly, no leaks or open ports, I've sprayed brake clean around the intake/carb base and there was no variation in rpm, however if I hold the choke door shut, it goes from idling at 2500 rpm, down to between 1500-1000. Turning the idle screws does nothing, I blew compressed air through the circuit to clear it out. None of the linkage is obstructed either. I've messed around with the timing, and the rpm only goes down when I retard the timing to the point where the engine wont even rev. I find people on forums with the same issue, but can't seem to find a solution what the hell do I do?

Update: had to change the throttle cable routing completely because it wasn't long enough.
 
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Snotty

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Your idle should be 750. Do you have a spring on the throttle to bring it back?
 

Davea Lux

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If you have the throttle spring installed, be sure the base gasket on the carb is not interfering with the throttle butterflies closing properly.

Dave
 

The Goose

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Not trying to be funny- who rebuilt the carb and what is their skill level?

If the carb wasn’t put back together correctly it’s never going to work correctly. If skill level is in any doubt I’d replace w new. I do not trust auto shack rebuilds either. A lot of junk right out of the box rebuilds out there.

Anymore with the near 100% water based carb cleaner we have to deal with in California I just replace with new. I think of an old carb now like I do old tires. Just buy a new one and go from there. The days of real cleaners that’ll take your skin off and CLEAN are over.

Keep in mind if the carb isn’t right no amount of tuning will fix it.

Good luck with your repair.
 

MEV

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you are holding the choke door CLOSED and you see the RPM drop? That is what is supposed to happen when you cut off the airflow to the primaries.
 

CBODY67

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With the longer/re-adjusted throttle cable, will it now idle down into the 600rpm range for hot base idle speed in "P"?
 
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