I'm in the process of rebuilding a couple of Q Jet carbs. Is there any difference between brass and phenolic floats?
personal preference in many cases, you will get people that say "never" use one of those kinds. I personally like to use the phenolic floats. I have pulled apart and built 100's of carbs, and I have only seen one phenolic float that had lost it's ability to do the job. I have seen several brass floats with a pin hole at the joint, and filled with gas so it doesn't work properly. Not a huge difference, but a difference.
The last 3 phenolics I put in only lasted a year before sinking. talked to a few guys who had the same problems...seems the gas additives were chewing them up. They may have a better coating for them now...this was a few years ago. Just my personal experience.
I think brass is the way to go as long as you check them for any leaks prior to install. Out of all the rebuilds I've had one brass with a leaky seam. A little resoldering and it was good to go. Once they're installed there is never an issue with them failing.
One other thing to consider here also is that the switch from MTBE to ethanol MAY reduce the failure rate of phenolic floats. Ethanol is not entirely without vices, but my research indicates that MTBE is some really nasty stuff. my opinion is that ethanol is not sustainable, due to the increases in its requirements, but we'll see. Phenolic will, in my opinion, always be more sensitive to fuel composition than brass.
The last time I opened up my Q-Jet was in 1991. The float I took out was brass, and it had a small pinhole in one of the soldered joints. I replaced it with a phenolic float. It still works like the day I put it in. In fact, other than changing the secondary metering rods or the hanger, I haven't touched the carb.
Do you use the same float setting with both type floats? What float measurment do most of you use on a 450-475 HP eng with fair vacuum?
Id have to say brass long as you check or even re-solider the joints even when new. They are either made at 900MPH on a machine or by hand for 3cents each in a 3rd world country so neither is gonna get them all right, 100% of the time. Id only say that from the report of Phenolic being messed up by gas addtives. I got a $15 brass float from NAPA though I have yet to install it. My car bis new still under warranty and didn't want to crack it open yet.
I think it is personal preference as to which one is better, thats why I carry both plastic and brass in each Q-Jet float that I carry.
The currrently available nitrophyl floats are fine for use with modern fuels. We have sold or used in carburters built here over 3000 of them with zero failures, problems, complaints, etc. The new design is a very dark color, chemical resistant and closed cell. The old factory style floats were light in color and will fail 100 percent of the time in contact with modern fuel(s). I tried brass floats in the shop back in 2001, and had three failures in the first month, all from very tiny leaks in the soldered joints. Since then we only use and sell the nitrophyl floats, and have a few of them going as fast as low 9's at over 150mph!......Cliff
