i have a 42 pencil lip flathead with a isky 3/4 cam 2 super 97 carbs and lately i get a stumble at the hit of the gas i tuned it up with new plugs i put new accelerator pumps and it's still there. any ideas ?
I'm not sure what a "pencil lip flathead" is? Are you using the small air cleaners? if so remove them and try that. I had KN ones in mine and it was starving for air, so bad it fouled my plugs.
So have you checked to see that the new accelerator pumps actually work? With the engine not running, look down the carb throat and move the throttle to full throttle. You should see a good, constant stream of fuel coming out of the accelerator pump discharge.
a pencil lip was cast in 41 and 42 you can balance a pencil on the block over the cam gear cover and it has a 1/8 razed outline of the intake gasket on the top of the block all the others are milled flat don't ask me why but it is this was only done in 41 and 42
Super 97's, sort of a oxymoron isn't it? You know what they say, 90% of carb problems are electrical.
Junk carbs. Get rid of them. As Bruce would say. “ try giving them the Naval Flotation test. Try changing your condenser. What type of distributor are you running??
Have you tried moving the accelerator pump push rod to the other hole on the throttle plate lever. Strombergs have 2 pivot holes, one " summer" and the other "winter". I don't know if the Speedway carbs have those and your stumble may be rich mix as well as lean. you might try "tweaking" the linkage to get the pump to move sooner. I assume you balanced them with a Unisyn.
I think the proper description is a “raised deck” describing the intake manifold surface on the block.
Like Glen wrote. If the initial timing is off you will get that feeling the accelerator pump is not working. Advance the distributer and i bet the issue goes away. Flatheads run really well when the initial advance is between 8 to 12 degrees. The stock advance was about 4 degrees not very good at all. Ronnieroadster
Do you know what the 'transfer' slot is? Dunno about the 'Super' but the original Stromberg have a single hole at the edge of the throttle blade - modern carbs have a slot - as the throttle blade sweeps to open, this hole sees engine vacuum and fuel flows thru it before the accelerator pump delivers its shot. This happens in millisecond type time. The stumble is caused when this hole or slot is overly exposed initially, the throttleblade should be shielding this hole at idle, the only fuel flow will be thru the idle circuit (the idle discharge hole will be just below the transfer slot hole) and when you open the throttle the throttleblade sweeps past exposing the transfer slot/hole to engine vacuum and fuel will flow from it before the accelerator pumpshot. The stumble occurs when the transfer slot/hole is initially overexposed like if the initial idle speed is too high. Very common for this to happen. Can you pull a carb, identify the holes I describe and take a photo showing the throttleblade and the hole?
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