NH Carb lighter float. Advantage?

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Model T Ford Forum: Forum 2016: NH Carb lighter float. Advantage?
Top of pagePrevious messageNext messageBottom of page Link to this message  By john kuehn on Saturday, December 17, 2016 - 09:46 am:

I ordered some new NH parts to rebuild a couple of NH carbs. When ordering I noticed the replacement float is a new lighter design. My floats were still good. No leaks and etc.

Does a lighter float help the needle to seat faster or better? Thanks for any explanation.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Mark Strange - Hillsboro, MO on Saturday, December 17, 2016 - 10:01 am:

I would think that a lighter float would more likely result in a slightly lower fuel level in the bowl, which may lean the mixture slightly. If the carb was running well before, you may have to reset the float level with the lighter float to restore the original fuel level in the bowl. :-)


Top of pagePrevious messageNext messageBottom of page Link to this message  By Stan Howe Helena, Montana on Saturday, December 17, 2016 - 11:44 am:

The new "lighter design" is to hopefully bring the brass float back to the weight of the originals as some of the ones coming out of India weighed far more than they should have. They also nearly all leak after a short time. Supposedly the new ones are better.

The float "buoyancy" is a combination of the size -- the weight of the fluid displaced by the float - less the weight of the float pulling it down.

Heavy ships sit lower in the water than light ships of the same displacement.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Charlie B actually in Toms River N.J. on Saturday, December 17, 2016 - 01:12 pm:

I'm not sure if a slightly heavier float would make a difference. As long as it floats that is. A leaking float will get heavy enough not to work but as long as it can still float to a degree it'll still work.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Scott Conger on Saturday, December 17, 2016 - 04:58 pm:

Charlie

see Stan's last sentence

the float will work, but will sit lower (or in other words, the gas level will be higher).

Yes, it will work, but you will not be able to set the float valve closing by the book (distance of float to flange)


Top of pagePrevious messageNext messageBottom of page Link to this message  By Charlie B actually in Toms River N.J. on Saturday, December 17, 2016 - 07:45 pm:

The way I see it is a heavier float would take more fuel to lift it off say the bottom of the bowl but once it's up it'll shut off the fuel if it's set correctly same as a lighter one.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Hal Davis-SE Georgia on Monday, December 19, 2016 - 12:43 pm:

A heavier float will have to be pushed further up than a light one to shut off the fuel. Result? A higher float level than intended.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Hal Davis-SE Georgia on Monday, December 19, 2016 - 12:44 pm:

Should have said higher fuel level in the float bowl than intended.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Harold Schwendeman - Sumner,WA on Monday, December 19, 2016 - 01:38 pm:

Hal - That's an interesting thought. Only had one cuppa' coffee this morning, but it seems to me that once the float has pushed the needle up into the seat far enough to stop the inflow of fuel, it wouldn't care how much or how little the float weighs, but it also seems that once the needle is seated, that alone dictates the float level.


Top of pagePrevious messageNext messageBottom of page Link to this message  By john kuehn on Monday, December 19, 2016 - 02:15 pm:

Thanks for the explanation about the float weight. I was thinking a 'lighter newer design float' had something to do about better needle seating.

I did order a new needle and seat. Its advertised as a new and improved repo of the original NH version. The viton tipped needle and seat set that was in one of the carbs wouldn't stop leaking for some reason.
After a day or so I would go out to the shop and it was leaking.
Hope the original style will work. We'll see.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Hal Davis-SE Georgia on Monday, December 19, 2016 - 08:09 pm:

Harold, think of it this way. If the float is heavy, it sits lower in the sea of gasoline. More of it is below the surface than if it were light. So, it takes a higher level of fuel in there to make the top of the float reach the needle to turn off the fuel flow.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Stan Howe Helena, Montana on Monday, December 19, 2016 - 08:20 pm:

The top of the float does not have to reach the needle. Only the tang on the float needs to reach the tip of the needle. The heavier the float, the lower it will set in the sea of gasoline. Therefore the level of the fuel in the bowl must reach a higher level in order to provide enough buoyancy to raise the float to the level where the tang of the float will cause the needle to shut the fuel off.

If you don't believe it, take a good float that holds the correct level in the bowl. Add Solder to the float and check the fuel level in the bowl. At some point the buoyancy will fall to the level that the float will not rise far enough to shut the fuel off and the needle will continue to flow fuel.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Roar Sand on Monday, December 19, 2016 - 10:02 pm:

What hasn't been touched upon, is the volume of the float, in other words the buoyancy, weight versus volume. Does the new one have the exact original dimensions?


Top of pagePrevious messageNext messageBottom of page Link to this message  By David Dewey, N. California on Monday, December 19, 2016 - 11:07 pm:

John,
Unless things have changed very recently, you will have to re-work the new needle for it to function. They are too rough and need to be stoned and polished--fairly easy to do in a drill, easier in a drill press and really nice in a lathe.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Hal Davis-SE Georgia on Tuesday, December 20, 2016 - 07:28 am:

Stan, I omitted that for the sake of clarity.:-)

Roar, good point. Technically, I suppose it is really a matter of the density (Mass per unit volume) of the float rather than its weight (mass) alone. One could make a lead weight that was the same weight as the float, but it wouldn't function very well as a float, so yes, the volume is certainly an important part of the equation.


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