CFD244 said

Hi Folks

The facts..........

Fresh 340 (with about 2hrs run stand time) with 9.3 CR, running a Comp XE262 cam. OEM intake with a 1972 TQ.
Base timing 20* btdc (MP gold shaft distributor.) Engine installed on a run stand, all warmed up..............

Smooth idle at 850 rpm pulling just under 15 inches on the vacuum gauge. Needle dead solid with 20* on the timing light. A/F 12.8

Run it up to 1700 rpm and I see an erratic vacuum needle in the 18-21 inch range. Timing light shows a solid 34* with the extra 14* coming from the ported vacuum signal.......Disconnect the can, back to 20*. A/F 14.2

So my question, does the erratic vacuum signal at 1700 rpm sound normal?

Thanks FABO

EDIT: Vacuum signal measured at the rear port on the carb. base (not the dashpot fitting)

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