RR, if you have a Nitrophyl float, (epoxy foam) you need a new float to first weight it to get a base line, and I am sure the density of the material would change from batch to batch when made. Back in the day, I checked the float very first thing pulling it out of the carb by using the back side of my fingernail and gently pushing a lower corner of the float and I if see wetness I change the float. Nowadays I just change it, if I can get a brass one all the better. I suppose if you wanted, weight the float get your number, then submerge it in fuel for a length time and then recheck.........
Are they all made the same?
IMO, I can't imagine a particular weight as a gauge to go by. I'm thinking buoyancy needs to overcome a pressure in a given range for the application. The know the outboards on my six pack tend to weaken over time.
Is there a flooding issue? Is it adjusted properly? How old is the float?
20 bucks for a new float is cheap compared to oil changes due to a weak float.
If you have brass floats, change over to them. I don't trust the black floats or the translucent plastic floats, I've had too many of them fail over the years. I DO NOT assemble a carburetor without brass floats. Of course, all I build are Holley units.
Never had a NP float fail. There is a way to test them. There is a weight test, 7.5 - 8gms.
Another method which I like better: the front end of the float has a section cut out. Sit float on a flat surface with this pointing up. Gently push down on metal end with your finger & then remove your finger. If float is good it will stay up in the air.