600CFM to 670CFM worth the effort?

PRH said
I can understand where the 670SA has developed a rep for being lean at WOT.
I’ve only run one on an engine on the dyno, and this was a very mild 455 Poncho making about 325hp…….mid-16’s A/F ratio at WOT.
A swap to one of the shop carbs showed normal A/F ratios, so no weird carb requirements from the engine.
The 670 had stock jetting.

There is a shop in town with a chassis dyno that tested quite a few cars running 670SA’s…….most(all?) of which were somewhere between “pretty lean” to “abort the pull” lean.
Some were cured with jets, others got different carbs.

I’ve seen/heard enough stories about unhappy customers running them to where I can’t imagine recommending one.

Is it just the jetting? I see they come with 65 jets in the primary which should be more 68 or 70 for that size of Carb.

I have also heard the issue is in the meter in block itself which is specific to the SA670CFM. Where the idle circuit is too lean, and it created a bog from Wot at idle.

I’m guessing the IFRs are tiny and cannot be removed\swapped this is why everyone drills them out.