Re: Stromberg 97 adjust
The Stromberg 97 is an extremely simple carb - it doesn't have a bunch of circuits to deal with - really has about 4 things you can tune:
1) Idle - using a combination of the throttle plate screw to set the air flow and associated RPM and the mixture screws to adjust the rich/lean at idle. Like most carbs, you turn them in until the engine starts to stumble a bit, then back them out about 1/4 to 1/2 turn.
2) The main jets control just about everything off-idle (except for the enrichment circuits). Typically you'll find that the higher-speed RPMs might be a tad richer than you'd like, but you'll need the larger jets to overcome a too lean condition off idle.
3) The power valve does just what the name implies . . . a bit similar to the Holley vacuum operated valves, but strictly mechanical.
4) The accelerator pump has two slight adjustments - the 'W' for Winter and 'S' for summer (supposedly). On my larger cube, big cammed engines, I tend to always use the largest stroke I can get - which is the 'W' setting. On Stromberg 48's you only have a single setting - though you can swap 97 bases onto 48's and get the two position adjustments.
When using an O2 meter to measure my AFR, I find that in order to make it run the best under all conditions, I have to live with a richer AFR at higher RPMs than I'd like - closer to 12 - 1 (284 cubic inch engine, ported, big valves, big roller cam, etc) . . . though there are no viable means to adjust both the higher RPM AFRs and not impact the lower RPM AFRs. These carbs are simple - which means not too many adjustments! LOL
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