Thread: Recent FE 390 Rebuild. Engine Bogging when 4 Barrel kicking in. New Carb installed

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What is your initial timing set at?

Be sure you are checking timing with vacuum advance plugged and idle speed below 800rpm. Big cams need more initial timing to get them to idle, if your idle speed is above 800rpm your mechanical advance could be starting and messing with your initial setting. Edelbrock carbs run just fine on the street, they just tune a little differently than Holleys. But regardless of the carb type you have, you will need to tune your ignition and carb to work with your motor.

Intermediate hesitations are often caused by carb idle incorrectly set and not enough initial timing. Bogs (sometimes with pops) are usually caused by accelerator pump adjustment too lean. The performer carbs use a weighted secondary valve and seldom is this the cause of any bogs as it opens with venturi vacuum.

Depending on the cam you have, your motor may need more initial timing, which will increase idle speed allowing you to set the carbs idle speed adjustment lower, which in turn sets the transition slots in the carb’s primary throttle body better. Once the initial timing is set to the liking of your motor to get it to idle correctly, you will need to check and adjust total timing to prevent detonation. Once the total timing is set, it is time to set the mechanical advance curve to match your motors needs. Now you can start adjusting the carb’s other circuits, such as accelerator pump, primary and secondary jets and metering rod circuits. Fortunately, Edelbrock provides excellent instructions on how to do all the adjustments.

Everyone thinks you can just throw a cam in it and go, but it's the tuning that makes it go.