Pump gas is also not good on this stuff. Have had this occur before. O rings shrink and get hard.

Q is not supposed to be left in the fuel system. Says on the can.

You can buy the o-rings at McMaster-Carr, 3.61 for 100. Part Number 9452K16, Make sure the surface the ring seats on in the bowl doesn't have anything stuck in there or pitted, also make sure your floats are not heavy. A cheap small gram scale will do it, float weight at the link.

https://www.tapatalk.com/groups/racingfuelsystems/holley-float-weights-t31.html

In addition, I use Vaseline on the needle n seats when installing em.......

I chased a problem like that a couple years ago and it turned out that the new foam float I got was molded a little off and it hit the body of the carb inside the float bowl so it would stick open and not shut off. So once I found it I filed the foam a little bit to cure the interference and then sealed the filed spot with clear nail polish and it's worked well ever since.

And how I found it was by removing the needle and seat from the assembled carburetor and then bending a small (~1/8") right angle hook on a paper clip and sticking it into the hole from the removed needle and seat and hooking into the tang on the float arm and gently trying to move the float up and down. When I compared how much the paperclip and float moved when the float bowl was off the carburetor to how much it moved when it was assembled (and hitting internally) it became very apparent that something was wrong there.

So I ordered a 10 pack of o rings off of ebay. Shipped $11.25
Was cheaper from all carbs but I'm ok with it.
I did order 4 new needle and seats from Summit.
The o rings showed up 1st. Lol
So i picked out the old o rings and sure enough they were brittle and just snapped off.
Going to install the needle and seats in a few after lunch and see if the problem is still there.
Hopefully this was the fix. The needles were cleaned and they move freely.

Are your new O rings Viton, neopreme or what are they made of?
Love that Q16, don't we

I believe they are viton.
I'll have to check but I just installed them and they are a nice tight fit.
Adjusted them to where I think they should be and NO MORE FLOODING.

And yes this Q16 is nasty stuff.
And I do drain the bowls after each use.

Putting this on my maintenance schedule.