Page 1 of 1
Holly NH Float adjustment
Posted: Mon Apr 18, 2022 9:10 pm
by jiminbartow
I have always adjusted the float on my Holly NH to 15/64” from the machined flange to the flat top of the float. When I took my carb apart yesterday to make necessary adjustments and install new gaskets, I was surprised that the float measurement was 5/32”which is quite a bit less than what I set it at. How does the float measurement change over time without being touched? I’d like to know in case there is a way to prevent it. Jim Patrick
Re: Holly NH Float adjustment
Posted: Mon Apr 18, 2022 10:26 pm
by Steve Jelf
Is the upward force of the float enough to bend the brass tab pushing the needle enough to bend it over time? I can't say for sure, but I doubt it. Does the needle have a rubber tip? If so, maybe it's become compressed. Anyway, your ¹⁵⁄₆₄" is correct, though I suspect ¼" is close enough. I agree ⁵⁄₃₂" is too high.
Re: Holly NH Float adjustment
Posted: Mon Apr 18, 2022 10:38 pm
by jiminbartow
Thank you, Steve. The tip is rubber, but it is firm and sharp and does not appear to be compressed. When I filled the gas tank the carb did leak bad and I immediately shut off the valve so I figured the carb cup had to be overflowing because the float was 5/64” higher than it should have been allowing too much gas in before the valve closed. Thanks again. Jim Patrick
Re: Holly NH Float adjustment
Posted: Mon Apr 18, 2022 10:46 pm
by Scott_Conger
Jim
I have to wonder if perhaps you failed to reinstall a gasket under the float valve body when you changed gaskets, or the new gasket is a little thinner. The amount of extra travel you have on your float would equate to just about the thickness of that gasket back toward the hinge. Remember, the measurement is at the free end of the float, and the height of the float valve is immediately opposite the hinge/fulcrum. It would take only a very small change in the gasket thickness to appear as a large change at the free end.
Re: Holly NH Float adjustment
Posted: Tue Apr 19, 2022 9:55 am
by TXGOAT2
In addition to the above, I would add that even a slight amount of wear at the float pivot or a very slight distortion of the needle or its seat could cause a significant change in the measured float level. Model T engines vibrate, and vibration can usually find a way to affect fine adjustments. Wear can also occur at the contact point between the float and the needle itself.