Rochester carb tuning/timing HELP!!

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Aug 8, 2004
Gig Harbor, WA
Just installed a rebuilt vac advance dizzy installed with petronix. 99.9% sure its not 180 out.Installed new cap, rotor, plugs and wires. Hooked up a hose from dizzy vaccum to a barbed fitting i installed on firewall side of rochester carb that had been plugged by previous owner(has suction when slightly higher than idle.) Using timing light on the flywheel i can get the idle running pretty smooth, but i cant tell how many degrees before top dead center i am because there are no markings, just the needle and a white raised dot on flywheel. Anyways, after twisting the dizzy i can get the idle sounding great! soon as i touch the gas, it sputters and wants to die. I move the dizzy in every damn position and when i touch the gas it f***** sputters, misfires, hiccups, etc!!! It didnt run that well when i bought it before replacing GM dizzy either. Im assuming its the carb and im wondering if ANYONE can give me some help or a link on how to adjust it. And I know at least one jackass will post in this thread to "get a stock carb" or "ditch the rochester." But now im broke and im trying to make the best of what ive got. So i dont need to hear it. Sorry this is so damn long.
I was there myself. Take a look at your points, that is what messed me up. I am not sure what petronix is, but if it has points you need to take a look at them. Also, check your fuel filters. Do you have the 2G carb? Also, make sure your choke is working properly, and the air jets aren't too high. I have a book I'll sell to ya for dirt cheap on Rochester carburetors, helped me when I had mine and for rebuilding it. Hope that helps!

Ben, since BOTH barrels on the Rochester open simultaneously, vacuum drops off VERY QUICKLY. The carb is set up with a mechanical accelerator pump to supply a spray of gas during the lag time immediately off idle. Check for a strong, steady stream on the accelerator pump.

Finding out what your vacuum reading at idle is wouldn't hurt either.


Mark A.
FineWyns-Petronix replaces the points and its not the fuel filter since i just replaced it. I pm'ed you about the Rochester book.

Mark-I'll check for the strong steady stream on the accelerator pump. Im gonna get myself a vaccum guage today as well. Thanks.

Also, do you normally use the timing light on the flywheel ? There is a needle by the flywheel and the raised bump on the flywheel itself that supposedly is 7 BTDC. How am i supposed to tell how far 10 BTDC is without any kind of markings??
Ive got one that was on my 76 from the po...couldn't figure out why it was running so rich...soaked it, rebuilt it...put on a weber and found out it wasnt the carb.... engine floated-lost compression...anyway, I have one I will sell you cheap.
Well, sprayed some brake cleaner around the intake manifold and it seems ive got a leak.:( I'll come back to this thread after i get some new gaskets installed. Thanks for the help, i may need more later.

40's-rock- Thanks for the offer, but im gonna make this one work, after i replace the gaskets on the intake/exhaust/carb/etc.

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