Engine Stumble at 2100 RPM
 

Twin 502 Cu In. Gen VI big blocks
Stock motors 450 HP at the crankshaft.
In 292 Formula SR1
Problem :
Getting up on plane I have a stumble in both motors at around 2100 rpm's getting on plane.
It is not an overpowering stumble and goes away quickly.
I do run high test gasoline .
Fresh spark plugs gapped.
Timing on the money
New Cap
New Rotor
Wires good.
Holley dual feed 850 double pumper carb.
I have had this problem since I repowered several years ago.
Once I get passed the stumble the boat runs perfectly.
I have both motors out and are about to toss them back in someone said I should figure out what jets are in the carb now and buy the next two size up jets.
Toss in the next size and see what happens.
My spark plugs were not fouled at all and their color was dark brown !
Does anyone on here have any suggestions.
Thank you in advance for the reply !
Big Boys Toys

Quarter turn out of the idle mixture screws should solve that issue.

if they are stock engines then they are only around 8.2:1 compression so stop running hi test. the engine was designed to run on 87 octane. anything higher and they actually lose power as the fuel will not burn completely.

Sounds like a carb issue for sure. Probably something with the secondaries on the carb opening and a lack of fuel or getting too much fuel.

and fuel pressure readings thru out rpms are ? carb and or fuel delivery issue(s) IMO

may need to bring the float level up

If adjusting the idle mixture doesn't solve the issue, go up one size on the power valves...that'll fix it

i also think the power valve is wrong,easy fix.

I have seen it on a Rochester with a little corrosion the power valve would stick and do that. Different power valve design so I would say not corrosion. Try a bigger power valve and see if it gets better or worse