[PunchT37]

Originally Posted by steve25

Call me nuts, but I fail to see correlation as to how a certain size / cfm carb will start an engine better cold then another size carb if there both set up right .

You’re not. These were out of the box. The 650 had the best factory idle circuit for this motor.

[Dragncar]

Originally Posted by PunchT37

You’re not. These were out of the box. The 650 had the best factory idle circuit for this motor.

340 is a pretty small engine with a short stroke. Its going to move air faster though a smaller venturi like the 650 DP has.

[HWYSTR455]

I can attest to the smaller carbs having better idle and off-idle drivability. Cold warm-up too.

On my Olds 350, the 670 avenger was great, but it flattened out around 45-4800 RPM.

I switched to a 770 and it pulled past 6000, but idle and drivability suffered.

There was really no in-between, and with the 670, as I would go into higher altitudes, it would lean out and overheat.

So I switched to a Holley Terminator throttle body setup. Problem solved. I'm sure timing control had some to do with it too.



.