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Old 10-09-2012, 05:24 PM
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Quote:
Originally Posted by 69novassguy View Post
ive been struggling with misfires for a long time now and finally realized im running so rich that it fouls the plugs. has anyone had this problem? and what size jets/metering rods should i use for a 350 sbc?
I've heard more complaints of the carb being too lean out of the box than too rich. The first thing I would do is baseline it back to stock and see what it needs from there, if anything.

Owners manual for Performer and Thunder series Edelbrock carbs. It has tables showing how the carb was delivered originally as well as what changes are needed to go richer or leaner.

Another good source of info is Edelbrock carburetor tuning.

FWIW, a ZZ4 SBC ended up needing:

primary jets- 0.113"
secondary jets- 0.110"
metering rods: 0.073" x 0.037"
silver (8 in/Hg) metering rod springs
pump rod in the top hole

But the thing is, every engine, vehicle and situation is different. Changes in the parts used, fuel, gear ratio, weight, how the vehicle is used, even ambient conditions, etc. all can have an effect on what the carb will need to work the best.

Not to mention the ignition timing. What's often blamed on the carb is in reality the timing/advance curve being wrong for the engine. The timing should be set up first, then dial in the carb. More on timing can be seen here. The article was written on the GM HEI, but the timing info holds true, regardless of the type of distributor/ignition.
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