Carb Floats, brass or Nitro ?

[Robert M.]

I know this has been answered before, but I failed to find it in the archives. I am going to do a rebuild of my Rochester 4MV '70 Quadrajet.
Do I want to use a new brass float or the Nitro float.

[Steven H.]

Re: Carb Floats, brass or Nitro ?

Robert,
I have always had the best results with the nitro style of float.
I just replaced the brass float that came in the rebuilt Q-jet on my '67 GTO. Never could get that carb to feel right so I finally took the top off and saw the brass float. Replaced it with the nitro float with the correct float level and WOW, that really woke the engine up. Now there is no flat spot from off idle and the idle is much smoother and responsive.
If you want to learn more about the Q-jet, I recommend getting Cliff Ruggles book on Rebuilding and Modifying the Q-jets.
Excellent reference. I have picked up alot of info from this book.
Sorry about such a long answer to your question.
Best of Luck!
Steven

[Joe L.]

Re: Carb Floats, brass or Nitro ?

I know this has been answered before, but I failed to find it in the archives. I am going to do a rebuild of my Rochester 4MV '70 Quadrajet.
Do I want to use a new brass float of the Nitro float.

Robert-----


I agree with Steven. I used to think the brass replacements for the Q-Jet floats were a good idea. Experience proved otherwise. I now recommend only the nitrophyl-type floats. Yes, they are life-limited pieces and should be routinely replaced at least EVERY time the carb is rebuilt (even though they are not supplied with most minor or major rebuild kits), but they are the only kind that perform properly. That may very well be why Rochester used them rather than brass floats in the first place.

By the way, all Q-Jets DO NOT use the same float. So, make sure you get the right one.

[Clem Z.]

Re: Carb Floats, brass or Nitro ?

the density of the brass vs nitrophyl is different and all the float setting listed are for the OEM nitrophyl float.

[Jack H.]

Re: Carb Floats, brass or Nitro ?

I went through a nitro float about every 18-months from the time I had my '71 SB QJet restored by Jerry Luck. Appeared the long winter months of storage + alcohol doped modern gasoline took their toll on the integrity of the nitro coating on the float.

Finally, I shopped for a brass replacement and found several available from Filko in various geometries. I used Filko's suggestion as to which unit to use for the geometry of my original Rochester part and it installed without a hiccup.

That was about eight years ago and since I've logged +50K miles on the car without ANY complaint... I noticed Jerry Luck mentioned he's now using brass floats during his QJet technical seminar at the recent NCRS National Convention.

[Clem Z.]

Re: Carb Floats, brass or Nitro ?

when i rebuild any carb with a nitrophyl float i weight it on a gram scale. they weight between 8 and 10 grams depending on the shape. if it has "soaked" up gasoline it will weight a lot more. i used to replace them every rebuild but i have learned that is not necessary unless the float is "heavy". octane boosters will eat thru the coating on the float and even eat thru the plating on the inside of the carb

[Robert M.]

Re: Carb Floats, brass or Nitro ?

Well the consensus seems to be go with the nitrophyl float, with Jack being the lone dissenter. Maybe an engineer from So-Cal will offer an opinion.