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2-bbl rochester poor idle quality

Posted: Sun Apr 26, 2015 1:20 pm
by themotorshop
i have checked the float 2- times and found that my mixture needles need to be out more then 3 turns and still there is poor idle quality,keeps hunting before it will finnally steady and smooth out,vac gauge fluctuates and is hard to adjust to get smooth needle reading,it does idle fair and accelerate fine, is there a possibility i should drill the holes in the throttle plates,the reason i say this is because i have another roch 2-bbl smaller bore from a omc engine,and it has the drilled plates,and that carb idles and operates flaulesly,any opinons would be appreciated,thanks

Re: 2-bbl rochester poor idle quality

Posted: Sun Apr 26, 2015 6:13 pm
by PackardV8
What year/make/model engine are we discussing? Is the carb original to the engine? A Rochester 2bbl can have been designed for a 225" or a 455" and they're very different inside.

Stock cam?

Some of the late Rochester 2-bbls had a serious problem when cold and just coming off the choke. Idle usually wasn't the problem when warm.

Re: 2-bbl rochester poor idle quality

Posted: Sun Apr 26, 2015 6:20 pm
by themotorshop
its a 307 pure stock motor running a mild 420 lift rule cam hyd, the number off the carb shows it was used on 307,350, and 400 so iam in the ball park,it is the large venturi witch i thought would be great,do you think i should drill the plates like previosly mentioned,that should give it better idle quality, i would think, thanks for the help,any further thoughts would be appreciated

Re: 2-bbl rochester poor idle quality

Posted: Sun Apr 26, 2015 6:21 pm
by themotorshop
also you are correct about running cold,it has no choke but until it warms up it wont idle correctly