Hot Rods Rochester 2g Idle Mixture Problems

I am working on tuning a Jet 2 barrel (2g carb). It idles really good but still rich. I started at 1-1/2 turns out, and kept working in with improvement. With both screws turned all the way in it runs great!?! Shouldnt it kill the motor? Any suggestions here?

 

Check your float level and check the needle and seat for wear or other damage. If the float level is set too high or the needle/seat is bad the fuel level can get to the main jet level and run over into the intake, causing an overly rich situation. If you have a vacuum advance distributor, be sure the vacuum lines are connected to the proper carb ports. The distributor line goes to the carb port above the throttle plate on most setups and any other goes to the idle port below the throttle plate. Not being that familiar with that carb I could be wrong on this. Anyway, a good check on all gaskets is advised, too. If it uses an economiser (power) valve, it could be leaking and cause your problem also.

 

What's the chance there is a vacuum leak?

 

Its a brand new carb, everything brand new. Is the pcv a possible source of vacuum leak? Hose is new, but maybe the valve is faulty. Ill try disconnecting it and plugging the line see what happens

 

I 100% understand that just because its new doesnt mean its right haha. Would just rather check other things before opening it up

 

Have you checked fuel pressure?

 

Well solved all my problems! Springs on idle mixture screws were fully compressing before needle was seating!! Grabbed some old springs and was able to get her tuned in beautifully. Thanks for the suggestions!!

 

Thanks for posting the answer; but why did a new carb have the incorrect (longer) idle mixture screw springs? What else is wrong with it? An issue such as you had makes the whole unit suspect!

Jon

 

A few years ago I needed a set of idle screws so I ordered a set. Straight out of “the packet” I could tell the springs would not work.

 

These are circle track carbs, likely this motor is much more mild and requires less fuel at idle then these are typically designed for. I know I will have to go down on main as well

 

OK, but, no offense meant, does not answer my question.

To my knowledge Rochester never sold a "circle track carb" new.

Thus, one would think that this is either an offshore new imitation, or an original Rochester that has been modified for circle track racing.

Decades ago, we modified a LOT of Rochester 2-barrel carbs for the circle track crowd. The $25.00 carburetor "claim" put an end to that business. But we never modified one such that the idle mixture screws would not seal.

Hope it works for you.

Again, thanks for posting your solution.

Jon

 

Jet Performance sells the circle track carb. They modify the original Rochester for racing. They arent cheap either $400, would expect better no doubt.

 

Thank you, that clears up the discrepancy, the carb is actually not new, as supplied by Rochester; rather one that has been rebuilt (modified, if you will). Still does not explain the longer springs, but since you found these, a moot point.

Jon