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Carb problem



I was on my way to my girlfriends work when I noticed the car wasn't tuning down. I believe its the choke but im no expert. You know when you first start the car, well mine anyways, it goes to around 1100rpm then you can punch it and she'll drop to around 750rpm. Well mine does that at first but then sometimes when stopping its kicks up again and makes it kinda hard to stop. It will idle at around 900-1000rpm(when its suppose to be 750ish) but if you put it in park it will go even higher to 1200rpm+. When I put the car in drive from park it jerks, kinda like if I was doing a N drop. There are sometimes while driving where I can take my foot off the gas and it wont decelerate... This problem started yesturday but its not all the time. This happens on and off. Like when I went to the gas station car was going nuts at 1200+rpm then drove right to gfs work, parked it and car ran at 750rpm... Sorry for the long post and I hope you guys kinda get what im talking about... Is there something wrong with the choke or what? How can it be fixed? I really want this carb to last until the end of this season because I want to do all the engine work in the winter while it sits so im not rushed or anything.

One more quick question. How much cfm does the stock q-jet for an 80 350c.i. motor pump in? What would be a good number to bump it up to? I was thinking 750cfm. What do you guys think?


Vettehead Mikey

Well-known member
Aug 26, 2003
Not that far from Ottawa
1973 Coupe
Your stock Q jet is already 750 CFM (some people 780) so you do not want anything bigger.

The erratic idle problem is common on these carbs and is usually due to the throttle butterfly shaft becoming partially jammed open in the baseplate due to wear. A rebuild is in order.


Active member
May 3, 2006
San Antonio,TX
1974 454 Stingray
It could also just be that the carb is a little bit gummed up.Try squirting some carb cleaner in it and see if that helps. I have experienced the same thing. The carb was just a bit dirty, and carb cleaner fixed it right up! Good Luck!

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