MTFCA Forum

Read in past posts about drilling out, cleaning and sealing carburetor passage ports. Works great and easy entry in the future….

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Does anyone really ever need to reopen & clean out the idle passages after the carbs initial restoration? Looks like wasted effort.
Is this an extreme example of OCD?

I guess it depends on the past use of the carburetor and current performance. This NH works very well at running speed but idled something terrible. Now cleaned out it performs great and archeologists 1,000 years from now will thank me for my work.
Besides that it too friggen cold outside today and I’m bored……

I like the idea of being able to quickly get into an area for maintenance without a lot of down time.

TOO COLD! your high shows 51* today our high is 19* with -3* tonight...I'll trade you.

That is how I have doing for a while. 7 blocks to ACE, buy the Allen heads, tap the hole, install with some sealer, done. Or find brass stock, cut, install, peen, file as needed. Guess it's a wash.

Anything under 60F is too cold for me……

Is it worth doing, with out a doubt. I don't drill out all the plugs but I make sure to drill out the ones that access every passage. I then spray carburetor cleaner through every passage. My chosen method of sealing is using 1/8" brass rod and peening them in place.

I just soaked an NH body overnight once in a can of lacquer thinner and after that the carb worked fine. Needed re-painted too!

A friend of mine has an NH in his '27 Tudor. Very recently it was running rough and would barely idle.
We drilled out all the passages and found them to be plugged solid. They were resealed with brass plugs.
We installed a new gasket set and did not have to make further adjustments.
The car idled perfectly following that small repair.
From that I would say that cleaning and sealing the passages makes a difference.
Harry

Harry

the NH idle circuit actually powers the car from idle to about 1/4 of the throttle movement. With that circuit blocked and the carb adjusted to compensate, the car will be lame for sure. 99% of the guys who either love to or simply must fiddle with their carbs all day long while driving with an NH are nearly all suffering from a blocked or diminished idle circuit. When properly rebuilt, while low on relative performance, the NH is a "set and forget" carb once the car has warmed up. The Kingston L-4 is, too, but tends to be hard on fuel mileage. Not entirely sure why they're so unpopular, but you have to pretty much pay someone to take one off your hands...in any condition.

regarding screws, I'm not a fan. I can plug a hole in 1/4 the time anyone can drill/tap/install a screw, and the repair will be undetectable in fit, finish, or performance as from the factory. On NH's, I consider a screw to be a blemish and not a feature.

To each his own. On the NH only one set screw is on the outside, is filled when painted and faces the engine so is unseen and certainly not a blemish….

Please clarify what this thread is about. Is it about “sealing” the carburetor ports closed? Why would you want to seal the ports that enable the free flow of fuel? Wouldn’t that be like sticking a straw in water, covering the end of the straw with your thumb and lifting the straw out and the liquid staying in the straw until you release your thumb from the end of the straw? That is what the vent holes in a carburetor do. I obviously don’t understand what this thread is about because it is hard to believe that anyone would condone sealing all of the vent holes in a carburetor. Please explain exactly what I am missing. Jim Patrick

Hello Jim,

This thread is not about plugging the idle circuit passage but plugging the access points to the passage. The NH shown in the first post is a center drain NH and has three passages drilled in three different directions to create the single idle circuit passage. It also has three plugs in the passage. The plugs are to seal the starting holes for the drilling of the three passages to create a single sealed passage.

On a related note the side bowl drain NH has a different configuration where the bottom bowl nut attaches and a forth plug. I do not remember other details at this time.

I will also add I have rebuilt many NH's and have never seen one that did not need the plugs removed and the passages cleaned out with a drill bit. Your experience may different.

Terry

Thank you, Mike. With the links you provided it was easy to place an order!

speedytinc wrote: ↑

Fri Jan 21, 2022 12:37 pm

Does anyone really ever need to reopen & clean out the idle passages after the carbs initial restoration? Looks like wasted effort.
Is this an extreme example of OCD?

I don't think anyone is necessarily suggesting doing this on a regular basis, unless problems have arisen, and then I suppose the screw plug makes an easy access. But for any properly restored NH, it's a must.

My source for brass plug stock was a package of brass wood screws that I had on the shelf. Those are easier to find than brass rod.

Brazing rod is plentiful in my shop.

Why not just mix up a bit of JB weld. Press a little in the hole and strike off the top and let cure. Seals it up but is easy to drill out in the future if needed.

Steve Hughes wrote: ↑

Sun Jan 23, 2022 6:36 pm

Why not just mix up a bit of JB weld. Press a little in the hole and strike off the top and let cure. Seals it up but is easy to drill out in the future if needed.

Is that what you've done?

There is the way it was done simply and originally, and then there is every other possible way. Not all of which have likely been tried, but no doubt, eventually will.

Jerry: Yes I have done that. It has worked well.

I dont question the NEED to drill out the idle circuit plugs & insure the passages are clear. I believe its manditory.

My questioning is why use set screws? Does any body really have to pull those set screws & clear the circuit after the first rebuild/restoration of a NH?

It always appeared to me an unnecessary task to remove all of the original brass plugs. Why deal with the difficulty of getting it all out keeping the drill bit perfectly aligned?
Personally I drill out the brass plugs smaller & re-plug with a piece of lead shot. Has not been an issue in the scores of NH's I have restored.
One shotgun shell does over 50 carbs.

In my effort to do the best job possible, I question a set screw's advantage also considering the extra unnecessary time.


FWIW. If I was to use set screws, I would use a taper tap & go in deep enough to have the screw self seal, like a pipe plug.

Do you really need to plug the hole in the flange? Will not the gasket do that for you?

On our motorcycles many have used solder and made a small ball of it. Then tapped it into the hole with a small hammer. Pick off the excess and you are good to go.

Steve Hughes wrote: ↑

Tue Jan 25, 2022 8:03 pm

Jerry: Yes I have done that. It has worked well.

Cool! Thanks!