Thought I was OK watching AFR readings, Idle AFR 13.0 (Idle was set by highest RPM method). Cruise 40-50 AFR 14.5. Then pulled spark plugs, rear engine plugs 5,6,7 & 8 are leaner/whiter than the front.
Trying to tune carb and fix a miss/weird stumble at idle. Engine runs smooth once RPM’s are increased, also seems to use a lot of gas.
When searching here I found a thread where AJ mentions manifold vacuum port at #8 intake runner, sure enough that’s were vacuum hose for brakes is connected. Seems like this could contribute to the problem?
Will move brake hose to rear center port on carb.
Also read about needing a different PCV valve with lower vacuum? Vacuum is 11.5 at idle.
Anyone have any input on why rear plugs may be leaner?
What about different PCV valve?
Any input is welcomed.
72 340 stock bottom end
Iron heads with new valves
Air gap intake with cool carb spacer.
670 street avenger #68 primary jets
Idle screws out 1-1/4 turns, idle speed 800-825.
Idle vacuum 11.5”
Hei with stock distributor and e core coil, 18 initial, 34 total.
NGK GR4 plugs gapped 44
Hughes whiplash cam.
4 speed, 323 rear
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