I have taken apart this Holley NH at least a dozen times, and it continues to stick open or closed. Got another Holley with the ball, and it works perfectly except for the power. The NH seems to have 20% more power.
Any Ides ???
Get a new shut off and ask (Lang's) for Larry Smith's one. They are exact repro of the original,and work very well.
Are you using the ball type on the Holley? If so that is the problem! It has been reported over and over about the Gross (ball type) and their problems esp in the pre 1927 T's or ones with gas tank under the seat or in trunk.
The ball type on my other Holley ( different style carb) works perfectly, just has much less power than the NH carb. I have both the telfon and the stainless steel needle and seat, both types on the Holly NH sticks, mainly open flooding and pouring fuel out .
Jamie in Bama
Look at the angle of the little tab which is soldered to the float, where it presses against the needle. It needs to be quite flat at that point, so that it pushes the needle straight up, not pushing it to one side. I have had no luck with the Grose valve. The needle and seat work best. There might be some leakage when parked (maybe a few drops a day) because of gravity feed so you need a good shut off valve in the system to prevent leakage when parked.
Never had much success here with the ball type jet in an NH. Throw it away and put a standard needle and seat beck in. No more problems.
I don't do many NH's but the ones I do I have to resurface the seat surface on the needle. The last batch I got you could see the cutting marks from the lathe where they were tipped. They were NOT ground to final finish as they should be. I am redoing the tips with 600/1200/2000 sandpaper and then with a fine India stone at about 6,000 rpm in a little lathe to get them to seat and hold. Some of the brass seats are also very rough. I have a little tool I made that is the correct angle for the seat. It just fits inside the hole where the needle goes in. I screw the seat into a special holder I made, insert the seat forming tool and give it a good smack with a small BFH. I have had to make a "suction test" holder that I then screw the seat into and tighten it, insert the needle and hold it with my finger, suck on the end of the holder and see if it will hold vacuum against my tongue. It is a waste of time to have to do this but if I don't, they leak. These are the ones they are selling as the exact duplicate of the originals. They leak. I just sent two straight through NH's back to Jay that have been back twice because the needle and seats leak. I had to replace the needles and seats AGAIN and do this to the new ones to get them not to seep. I didn't used to leak test NH's because they are so simple but with the quality of the needle and seat sets available I am having to spend the additional time to do it. I leave them on the leak test setup over night or at least for a couple hours during the day when I'm working in the shop.
If the needle and seat is good, there should be no leaks from an NH no matter how long it sets. (well, as long as the gas stays fresh, etc.)
This last batch I got were pretty scabby but what can we do? We are at the mercy of what the vendors sell. At nearly $15 a set I'd think somebody could make some quality needles. I had problems with the soft tip ones deteriorating in the ethanol based fuels so I went to these. They were great quality at first. Not so now.
I working on carburetor about #1500 today, it is on the leak test while I am in here having coffee and getting my feet warm. Now back to the shop. I was just going to read the car salesman thread but got hooked on the NH topic.
By the way, the new Holley G needles are no better. Maybe a little but I am retipping every one of those to make sure it seats, too. I don't like carbs that leak.
I have never replaced a Model T needle and seat in over 50 years . I polish the needle with fine emery then place it in the seat and tap it a couple of times with a plastic hammer and it leaks no more.
I've had the same problem as James many times. Click here to see how I fixed one recently:
James: If you get up to B'ham, come by the shop and see me. Dan
Give me a address and we'll cone visit early next week ?
James: Sent a PM. Dan
Never used the PM, I'll try to figure it out, but at 91 years young I'm slow, he he he
Also you can shoot me info at my e mail, email@example.com
James: Check your email. Dan