MTFCA Forum

How thick is the metal float for a NH center drain carburetor? .630 or .830
I also have two different sizes of float jets one has a .100 orifice and .375 outside diameter the other is .123 and .408 not sure which I should be using.
If you were going to have someone rebuild your carb who would you use.
Thanks

Regarding your jets; they are valves. The one with the larger orifice and body is an either an original, or a repro made to original dimensions. In either case it likely needs reworking. The one with the smaller orifice and body diameter is the standard replacement.

Tom I would have myself rebuild it. You cant get a simpler carburator than a Holly NH. Just do it yourself, its childs play

Tom: This 2017 MTFCA Forum thread should help.
http://www.mtfca.com/discus/messages/70 ... 1509980090

NH is a super easy build. I like them and haven't had one that didn't run good after a build.

Royce Peterson has a tutorial on how to do it on his Ford fix site.

Thanks for all the advice. The links and Royce’s page convinced me to do one myself.

You didn't say which NH you have. The float on my Ford NH is .625" thick.

Floats are everywhere. Just find one and put it in! I believe the original opening for the float valve is .125. For several years, all the T suppliers were selling .100, which doesn't allow enough gas to flow into the carburetor on a hard pull.

It’s a later model with center drain. It’s on a 26 touring.

The taller float came out in 1926 when they switched to the gas tank in the cowl.

Vaporizer carburetors also utilized the more robust float.

I haven't installed my small-float NH in my '26 yet. Will I need the thicker float? I assume that I would have to raise the float level to compensate.

Mark

the extra head pressure from the higher mounted fuel tank and very short fuel line combined with vibration often lead to a rich mixture on Improved Cars and were more prone to leaking past the float valve when sitting. The official fix for that was a thicker float, providing more bouyancy and more sure sealing at the float valve. The adjustment level remained the same. Your car will run adequately with the thinner float, but the thicker one will add a layer of certainty and consistent performance.

The reality is that most don't know there is or should be a difference; those that know, most don't care, and however the car runs, that's the way it runs. The fact that so many folks live for the thrill of constantly adjusting their NH for any given road speed or pulling condition tells me that there are a very large number of cars performing to their owners' expectations, but in a fashion that neither Henry nor his engineers ever would have tolerated.

Scott, thanks for sharing your information. My car has always run rich and had issues with the float not wanting to always shut off the gas flow. I’m going to swap mine and see if it helps things
Tom

Tom

you are most welcome
the other thing to look for is a worn float valve or a poor float valve to carb seat seal. The hard red washer against a pitted casting will very often leak, leading the owner to believe he has a needle/seat problem when he really has a valve body/carb seat issue. This is mostly manifested as a constant drip or flooding of the carb after sitting awhile (which is why you always want to turn the fuel "off" when sitting).

If you believe you have a bad washer interface, you are welcome to contact me off line for the solution to that.