Rochester 2GV question

1953 Homer · Oct 5, 2007

My '65 Chevy pickup has an '86 305 bored .030 over, but otherwise stock innards. I put on a Rochester 2GV (2 bbl) carb for a little economy, but have had a hesitation/stumble from day one. I find that my "ported" vacuum connection, that is connected to the advance can, has 20" of vacuum at idle! I thought it should be zero or very low at idle and increase as the throttle is opened. This gives advance at low RPM before the mechanical advance kicks in. What gives here? There are only two vacuum connections on the carb, both read manifold vacuum at idle (20"). HELP, I'm lost here. Idle speed is 600, idle is smooth but some surging at cruise speed can be felt, especially going uphill. Thanks in advance, get it? Mike

DoubleVision · Oct 5, 2007

Chevrolets are supposed to be connected to a full time manifold vacuum source at idle. That`s why in the past before computers and the timing adjustment was on the catalyst, it would read: Disconnect vacuum advance and plug.
If the carb has a dead spot I would suggest inspecting the squirters, make sure it has a full shot and shoots the very instant you move the throttle, this can also be caused by trash in the main circuits, vacuum leaks, or vacuum leak at the intake manifold. When you connect a vacuum gauge does the needle bounce alot? if so this can point to many things, but if you just swapped on the 2 barrel manifold and carb, you can almost bet it has a vacuum leak somewhere. Surging also indicates the mixture is too lean, so the carb is too lean or it`s got a vacuum leak.

Rochester 2GV question

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