Where Do I Begin
Foothills Model T Ford Club members posing for the camera at a club activity.
If you are new to the hobby and contemplating your first total restoration, don’t! Buy a car that is already restored or get a decent running original. It doesn’t need to be a show winner but should be a good runner. Often it is less costly to buy a restored car than it is to restore one, especially if you don’t have a well equipped shop where you can personally do the restoration. Doing a rigorous safety inspection and upgrading worn or unsafe parts will afford a good education and hone your
skills, and during the process you and your family will be able to tour and enjoy the car. If the rear end seems a little noisy, shop around for another one and restore it properly at your leisure. It only takes a morning to swap in the restored version. Sell the old rear end or better yet restore it as well and save it for your next car. If the restoration is going to be a family project it is especially important to get a car you can enjoy right away. Your children may not have the patience to wait years
before touring and you may not have the patience to deal with them when they get tired of sanding and scraping and cleaning. Join one of the international clubs and a local Model T club and serve on one of the committees. It will be fun and the knowledge you gain from the club members will be invaluable. In the process you may come to know which model of car you really want to restore and own and you and your family will enjoy the tours and make new friends. It takes way longer and
costs way more than you expect to undertake a proper restoration. If you are patient you just might meet someone who started a restoration with enthusiasm and good intention and who has now lost interest and is selling the project at a discount to get it out of the garage. Most antique cars are still sold by word of mouth. O, and don’t sell your driver to buy a restoration project. Before you buy, follow the inspection checklist posted at www.safe-t-handbook. com to verify that you have chosen a “good runner” for your first car. Re-spoking wheels ($1,000) or rebuilding a broken engine ($2,000 - $3,000) will take some of the fun out of your purchase so choose carefully. You will need space for your car project, space to work and a fair bit of storage space. Contrary to what most urbanites believe the family garage was not intended for parking your car over night. A two car garage has adequate room for repairing and even restoring a T as long as you are organized. You don’t have to own all the tools required to fix your car. If you don’t have an acetylene torch, a MIG welder or a lathe for example, you may need to make friends with someone who does. That is one of the reasons for joining a car club. Everyone has their own “workflow”. Some tear everything down and start with the chassis. Others start with the sheet metal one piece at a time, completing body work and primer and storing finished pieces away from the dust and grime of the shop. A digital camera, baggies and a
With luck you can find many of the parts you need at a swap meet or even in a fellow club member’s garage. marking pen are invaluable. Take lots of photos from several angles of every step of the disassembly. Don’t trust your memory. Label everything and take notes. Keep a restoration journal and jot down ideas for future projects. Save the paint code formulas. Keep a list of part numbers for bearings, seals and specialty parts. Discipline yourself to do this from day one and you save hours or days of searching, guesswork and frustration during reassembly. To set forth a logical
If body work is not your forté then leave it original and focus on making your car mechaniically sound. This roadster pickup photographed at the Model T Centennial in Richmond, Indiana is a sleeper. The engine features a T-Go overhead valve head and other performance eaquipment.
organization for this book the author has chosen to start from the ground and work up. The same is true of the “Comprehensive Inspection Worksheet” that accompanies this book. In fact, the book is intended as a support document for the inspection sheet and is more focused on repair than restoration. The Model T Ford Club of America has a series of restoration manuals and videos that are very helpful. The manuals are inexpensive and your local MTFCA chapter may have a set of the videos. A bibliography of other reference manuals is included in the back of this book. Don’t assume that your
Open the hood and it won’t be long before you attract enough interest to start a new club.
car still retains all of its factory parts. Your T has likely endured a fair bit of part swapping and rebuilding. Most T parts are interchangeable from one year to the next but that doesn’t mean that they should be interchanged. For example: pitman arms and drag links changed length
over the years and even thought spindles are interchangeable they are not ne rily compatible from year to year. This book is not intended as a catalog of the evolution of Model T parts but the author will point out some of the dangerous parts combinations.
Carburetion & Fuel Delivery The Mouse Trap was so named because of the trap door on the choke end that acted as a variable venturi.
Dozens of different models of carburetors were marketed for the Model T. Carbs manufactured by Holley and Kingston were installed at the factory along with the short lived Buffalo carburetor which appeared for a few months on 1910 cars. Most carburetors of Model T vintage
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were of the puddle type, thus described because a stream of air was drawn over a puddle of fuel drawing small droplets of gasoline into the torrent and up to the cylinders. Ever the minimalist, Henry relied on gravity to deliver fuel from the tank to the carb. The system worked OK but did have a few drawbacks. Gravity induced fuel pressure does not stop when the key is turned off. This is one of the reasons the T was supplied with a fuel shut off valve. Forget to turn off the valve and some day you will find a tell tale puddle of fuel under your car. A worn inlet
valve or piece of dirt stuck between the needle and seat will allow gasoline to seep steadily from the carburetor. Up to 1926 the gas tank was found under the seat not far above the
float level of the carburetor. If you are low on gas and the hill is steep the fuel level in the tank will drop below the inlet of the carb and the engine will stop. That is one of the reasons Model Ts were often backed up steep hills. There are at least two others. Reverse is geared lower and the band is usually less worn than the low band so reverse was more efficient. And, if the engine kills on a steep hill it is safer to have the nose pointed down than up. Carburetor design is a matter of balancing compromises. Optimizing for good idle and easy starts makes the mixture much too rich at speed. Good design for speed causes the carb to starve at idle. The first Model Ts were supplied with the Kingston 5 Ball and for a short period with the Buffalo carburetor. The Kingston is aptly named because five balls valves are used to manage the air fuel ratio. At low speed air entering the carburetor drops down over a puddle of fuel then up into the manifold. When the throttle is opened, increased airflow raises the balls from their seats feeding additional air into the mixture. The Kingston 5 Ball was superseded by the 6 Ball and 4 Ball and finally by the “flapper valve” L series.
Holley was the other primary supplier of Model T carburetors. The early, expensive, solid brass Holley carburetors eventually gave way to the cast iron Holley NH part number 6200. Ford apparently liked the design and soon after its introduction Ford approached Holley for a license which allowed Ford to build one NH for each one they purchased from Holley. Ford made similar deals with other parts manufacturers One this page: for coils and spark plugs. Kingston Y, 4-Ball If you are not con- P/N 4400 cerned about having the proper carburetor for the year of your car then the NH is a good choice. Restorable cores are still readily available at swap meets and on eBay. Restoration is straight forward and new parts are readily available. Straight Through The first NH, part number 6200, featured a straight through design which offered good air flow at speed. It had a side drain, angular float bowl, and long arm throttle and choke linkages. The threads in the post extended all the way to the bottom to allow for the short nut that attached the float bowl. The early “straight through” carbs had a brass air bleed screw at the end of the data plate. This was later replaced with a vent hole emerging under the data plate. Looking at the carb with the throttle to the left the data plate on the 6200 is upside down. View the swayback NH from same orientation and the data plate will be right side up. 3
Overleaf: Holly H1, Kingston L, Duffy & Beamer, Kingston 4-Ball, Gardner, Simmons Super Power
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Excerpt from a letter received from the Holley Carburetor Company: “Dear Mr. Ford: A situation which I consider unjust to us has developed at the Highland Park factory which I respectfully request receive your serious consideration. 1. A contract was made between the Holley Carburetor Company and the Ford Motor Company, September 1, 1920, in which the Ford Motor Company was given a shop right to manufacture our NH carburetor, the consideration being orders to be placed with us for 50% of the carburetors used on the Model T cars. From September 1st to June 30th we received orders for 34% of the cars produced. 2. We installed machinery to produce 5,000 carburetors per day. The above contract provided for one year’s notice of cancellation. This notice was given us on April 21st, 1921. Since that time, machinery has been installed in the Highland Park factory to produce carburetors known as Model F, which is identical with Model NH with the excep tion of a slight change in the mixer chamber venturi, as per sketch attached. We are informed that they have orders to produce 3000 of these carburetors per day while we have never produced more than 1,800 per day and have been laying men off a portion of each month. Mr. F.H. Diehl the Ford Motor Company’s purchasing agent replied: that not only was Ford making Model F’s, but that they were building Model G’s as well. And they were buying Kingston’s too. These documents suggest that Model T’s came with four different carburetors from Sept. 1, 1920 to Aug., 1921: The Holley NH with the straight thru design, the Model F, the Model G and the Kingston.” Research by Trent Boggess Henry Ford Office papers, accession 285, the Benson Ford Research Center at The Henry Ford 6
Swayback Ford never did produce the “straight through” NH but in late 1920 introduced a swayback venturi design p/n 6200B which was more effective at atomizing the poor quality gasoline available at the time. This restricted bore design made the engine easier to start and provided a smoother idle. Holley quickly followed suit. The data plate on early Ford built carbs indicates Ford F. The plate on later models reads Ford NH. In 1925 the NH 6200C center drain carburetor appears in the price books. This carburetor also featured a universal joint adjustment linkage. Holley vaporizer carburetors would finish out Model T production.
Performance The “straight through” breathes better at high rpm and so gives more top end power than the “swayback”. Some say that it is harder to start and doesn’t idle well. In my experience the carb starts and idles fine. It pulls the hills a better than the “swayback” and has a higher top speed.
Swap Meet Bargains Virtually every piece of the Holley NH can be purchased new, but not at bargain prices so look first for a
carb that is complete. Now check to see that the throttle shaft is free from play. A worn throttle shaft hole or shaft can result in a vacuum leak causing the engine to idle poorly. Surface rust is not a problem but deep rust pitting on the interior will affect the air flow through the carburetor. StraightThrough carburetors generally fetch more money than swaybacks. Comparison You can identify the 6200 (Straight-Through) easily by looking down the bore. It will have a round unobstructed venturi. To tell the difference between the 6200B and 6200C is necessary to remove the float bowl. The 6200 and 6200B have an angular boss on the post that accommodates the air inlet tube. The post on the 6200C is missing the boss a n d has a slot cut in the bottom to allow fuel to flow through the center drain of the more modern, rounded float bowl. Properly attired, the 6200C will sport a u-joint connector to the mixture needle.
Straight-through 6200 above, Swayback 6200 B below
Straight Through Venturi Swayback Venturi
P/N 6200C
P/N 6200 Angular Boss
P/N 6200B
P/N 6200C
Threads to Bottom
Slotted Post
Angular Boss
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Throttle Shaft Boss Choke shaft
6200 C
Vacuum created by th idling engine pulls fuel f the float bowl and air fr the air inlet through th two holes into the inta manifold.
Spray Nozzle
Low speed circuit Fuel sucked through the spray nozzle and mixed with air from the air inlet is drawn through this passage and ejected through the two holes in the throttle end of the carb.
Air inlet The air inlet draws air from under the data plate and feeds it into the recess surrounding the metering jet. This passage forms part of the low speed circuit.
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Drain Plug Boss Fuel Drain Slot
Fuel Inlet
Mixture Needle
6200 B
he from rom hese ake
0.71� diameter
Float Hinge Float Needle Seat Needle Taper 300
Air inlet
Float Bowl Nut Boss
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DIAGNOSING Fuel System Problems
Remember the old adage, “most carburetor problems are really ignition problems”.
The fuel inlet valve may also be called the float valve, needle valve or gross jet.
What appears to be a carburetor problem may actually be a problem with the ignition or even valve train. This section will focus on the fuel system only. One of the simplest ways to eliminate the carburetor as the source of a problem is to replace it with one known to work well. If swapping carbs with a fellow hobbyist fixes the problem then it is time for a rebuild. Even if your carb is in good shape keep your eye out at swap meets for a good “cheap” rebuildable core so that
you can have a quality spare, just in case. Carburetor Fuel Leak If fuel is leaking on your garage floor start by repairing the shut off valve. This will keep the floor clean and make your garage a safer place. (link) If gas is leaking out the choke end of the carb when the motor is running then the mixture is way too rich. The solution may be as simple as adjusting the mixture knob on the dash. Leaking through the choke end when the motor is not
During the 1960s and 70s Ansel B. Grose registered several patents for a fuel control valve which became known as the Grose Jet. His invention replaced the tapered needle with two steel balls. A large one that made contact with the tab on the float and a smaller which, when forced into a tapered seat, shut off the flow of fuel. This design was intended to overcome the tendency of the needle and seat to wear unevenly and had the added benefit of being impervious to alcohol enriched fuels which caused problems with the Viton tipped needles. The system works pretty well but has a few drawbacks. If the car sits for a long period without the engine being run the small ball can stick to the seat preventing the flow of fuel. In some cases debris from the fuel tank can become lodged between the large ball and the wall of the assemble preventing free movement of the ball. Like the Viton tipped needles the orifice is smaller than on the original valves restricting the flow of fuel which may pose a problem if you intend to drive really fast.
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running is an indication that the bowl is being overfilled. The amount of gas in the bowl is controlled by the float and the needle valve. When the gas level rises, the float rises and pushes the needle valve closed to shut off the fuel. As the gas is used up in the bowl, the float lowers and lets in more fuel. None of the other parts of the carb have anything to do with this so concentrate your troubleshooting to this area. Photo of float and float valves If there is any dirt or crud in the gas tank it can become jammed in the needle valve causing the leak. Sometimes the needle assemble will become gummed up from poor quality fuel, also causing it to stick. With the engine running tap on the side of the carb with the handle of a screwdriver to see if you can dislodge the offending dirt or loosen the stuck needle. If that doesn’t stop it, then it’s time to remove the carb and open up the bowl. With the fuel drained and the float in place, turn the carb upside down, suck on the inlet and put your tongue over it to seal it. You
should be able to create suction and feel it against your tongue. If the suction doesn’t last, then the needle/seat assembly is leaking. Verify that the seat is screwed in securely and look closely at the needle to see if there is a ring worn around the tapered point. If there is then it is time to replace the needle and seat. (link) If there is a good seal then make sure that the float is properly adjusted. The distance from the top of the brass float (opposite the needle) to the machined ridge that holds the float bowl gasket should be 3/16” to1/4”. This distance was ¼” to 5/16”
for the original cork float shipped with the early “StraightThrough”. The brass float is more buoyant and is not affected by the alcohol in today’s fuels. You will find the brass float more reliable. Now remove the float and shake it to see if there is any fluid inside. There is a discussion later in this article on how to repair the float. (Link) Hard to Start, Missing at Low RPM Adjust the fuel mixture using the knob on the dash. This may seem like a “no brainer” but it could be the mixture is simply out of adjustment. If the engine runs rough at low rpm but improves
with speed, check for an air leak at the carburetor flange, throttle shaft or intake manifold ports. The engine stumbling under acceleration is another symptom of this problem. An air leak reduces the vacuum and affects the atomization of the fuel. When the engine is running at cruising speed there is usually enough air flow to overcome the leak. The simple way to test for an air leak can be hazardous to your health. You can sniff out the leak with propane, ether, or even spray bomb carb cleaner. “Spray bomb” that is an unfortunate combination of words. Do this test when the exhaust man11
Note the mixture control rod located between the coil box and speedometer on this 1912 Trouring car.
If the engine is running poorly and you just can’t seem to find the problem check the gas cap to make sure the air breather hole is not plugged.
You may have felt a small static discharge through the vacuum hose when cleaning up around the shop. A static spark and gasoline fumes can cause a violent explosion and fire. Using a vacuum to suck the sludge out of a sediment bulb that is still attached to the gas tank can dramatically reduce your life expectancy.
ifold is relatively cool and the engine is running at low RPM. Using an unlit handheld propane torch direct the raw propane at the carburetor flange, throttle shaft hole, intake manifold ports and even the brass nut that holds the mixture needle in place. If there is a leak the engine vacuum will draw in the propane and make the motor run smoother and faster. The remedy for fixing a leak may be as simple as tightening the manifold clamps and carburetor flange nuts or you may need to replace the gaskets or repair a worn throttle shaft. If an air leak is not the problem then the idle circuit could be plugged. (see the section that follows on restoring the NH) Engine Won’t Start If the engine won’t fire and you are confident the problem is not ignition or valve related then the problem is likely a stuck float valve or blockage in the sediment bulb or fuel line. Tap the side of the carb with a small hammer or wrench. This may free the valve. If tapping doesn’t work then shut off the fuel at the tank and open the drain valve at the bottom of the carburetor. Check for water in the gas leaving the carburetor. If a lot of water is present you may have found the culprit. When the flow of fuel stops, remove the float bowl. Check to see if the float valve moves freely. If the valve is in working order then open the pet cock at the fuel tank and watch to see if the fuel flows freely through the fuel line and out of the valve. The orifice 12
in the valve is only 3/32” to 1/8” so judge the stream accordingly. If the flow is inadequate then look for a blockage first in the sediment bulb and then in the fuel line. After cleaning the sediment bulb remove the fuel line at the carburetor and blow air back through the fuel line. Reassemble everything and open the pet cock and start the engine. Missing at High RPM Missing at high RPM if most often caused by a weak magneto, poorly adjusted coils or a worn or misaligned timer. If your engine lacks power at high rpm, pops or backfires through the carb or surges at top speed then the problem may be inadequate fuel flow from the gas tank. Follow the procedure just discussed to assure as good flow of fuel from the tank but before going through all the fuss check the float hight (see previous page) Difficulty Setting the Fuel Mixture If the spray nozzle works loose it will be almost impossible to consistently set the mixture because as the spray nozzle loosens it will change the mixture setting. Additionally, fuel leaking around the nozzle will not be properly vaporized possibly causing the number 1 and 2 spark plug to foul. The mixture needle may also be at fault. If the threads are stripped or not meshed with the tapered threads in the carb body then adjusting the mixture control rod will have no effect. The steel part of the mixture needle is swedged into the brass shaft. If is comes loose then it will not be possible to hold a proper mixture adjustment. Too lean A lean mixture burns more slowly than a rich mixture. Two symptoms of a lean mixture are engine overheating, and backfiring through the intake manifold. A slow burning fuel mixture can still be burning when
ejected into the exhaust manifold which can cause the manifold to glow red. The slow burning mixture can also overheat the cylinder wall and cylinder head causing the coolant to boil. If the exhaust mixture is still burning on the intake stroke it can ignite the incoming gas causing an explosion or backfire in the intake manifold. An air filter can act as a flame arrester preventing backfiring through the carb from causing a fire. Opening the mixture needle will usually remedy this problem. Occasionally a small piece of debris will become lodged between the mixture needle and spray nozzle causing a lean mixture. This can usually be dislodged with the engine running by opening the mix-
ture needle and “gunning� the engine a few times. Too rich A rich mixture is indicated by black foul smelling exhaust smoke. Because of the design of the intake manifold, excess fuel condenses in the front of the vertical riser of the manifold and is drawn up into the number one and two cylinders often fouling the plugs. Dark sooty or wet spark plugs are also a symptom of a mixture that is too rich. Turn the mixture adjusting knob on the dash clockwise until the engine begins to misfire then open it gradually until the engine runs smoothly. Note that white exhaust smoke is an indication of oil entering the combustion chamber and can the result of worn piston rings or worn valve guides - or simply too much oil in the crankcase.
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Restoring the NH Check the carburetor for obvious problems: missing parts, worn throttle shaft or plate, wrong mixture needle. Begin a list of parts to order. To remove the throttle and choke plates you may need to cut and extract the wires that hold the plates in place. With a pair of pliers hold the plate securely and slide it out of the shaft. Check the throttle shaft and boss for wear. This is not so important for the choke. For the car to start easily and idle smoothly the throttle shaft and plate should fit snuggly in with very little or no play.
A worn throttle plate or throttle shaft will cause the Next remove the float bowl and float. Be engine to idle poorly. careful not to lose the float needle although in Since the choke is not all likelihood you will be replacing it. used constantly like the throttle the choke The most difficult part of the restoration is extracting the spray nozzle and float needle parts are unusually seat which are usually stuck in the not worn as much carburetor body. Soaking in and do not cause diesel fuel or penetrating oil a significant will sometimes work. Some problem even if restorers drill the seat and use they are. an “Easy Out”. Others use a
special hexagonal screwdriver available from the vendors. The easiest way to remove these fittings is with an acetylene or Map torch. Heat the carb body where the seat is located to a dull red. Be careful not to apply the flame to the brass float hinge. It will easily melt. Do this in a dimly lit room so you can easily see the color of the metal. Attempting to remove the seats while the brass is hot may cause it to crumble. Let the carb cool slowly or quench it in water, it doesn’t matter. The parts will then easily back out with minimal effort on the screwdriver. Be sure to clean out the old gaskets as well. 14
If throttle shaft hole (bearing) is sloppy you can drill it oversize and sleeve it back to 1/4”. New throttle shafts are available. For the carb shown above a 1/4” bit was used to line everything up and the a piece of 4” angle iron was used as a clamping jig. The hole was drilled with a 5/16” bit and then chamfered at the top to make room for an o-ring. The throttle shaft was worn but salvageable so rather then sleeving the carb body the sleeve re soldered to the shaft.
5/16” OD by 1/4” ID brass tubing purchased from a hobby shop was cut to length using a drill bit to keep the tubing from collapsing.
Brass has a greater coefficient of expansion than cast iron. When the carb is heated red hot the brass expands more than the cast and is squished inside the threaded boss. When the assembly is cooled the brass shrinks more than the cast and loosens. Heating and quenching tempers steel and anneals brass. Brass won’t take much heat. If you get it too hot it simply crumbles.
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Cut the top sleeve 1/16” shorter than the wear pattern to allow for a #2 (3/16”x5/16”) o-ring.
Early throttle aand choke arms are longer than the later ones. Both styles are available from parts vendors
The sleeves can be secured with Loctite or solder. Make sure the solder doesn’t block the throttle plate slot
The o-ring fits between the sleeve and the throttle arm.
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Chanfer the top of the throttle shaft hole to accomodate the o-ring.
In this situation the o-ring is overkill but it can also be used as a temporary fix for a leaky throttle shaft without adding the sleeves.
Center punch and drill out the brass plugs using a 7/64” bit.
Place all the parts you have removed in a plastic baggy. Now it’s time to clean out the interior passageways. Start with the vent that feeds air to the mixture adjustment needle. This passage draws air from under the data plate past the spray nozzle and up into the venturi. In later style carbs this passage is straight and can usually be cleaned by hand by poking a piece of coat hanger or small drill bit up through the bottom of the center post. If it becomes necessary to use a power drill be careful not to drill through the name plate. On early carbs p/n 6200 and 6200B the coat hanger is too thick; use a stiff piece of mechanic’s wire. If blockage can’t be removed in this manner then it will be necessary to remove the data plate and clean the passage from the top. New data plates are available. Next clean the three tubes that form the passage that feeds fuel to the small holes on either side of the closed throttle plate. This is the idle circuit and in an unrestored carb it is often blocked. Center punch and drill out the brass plugs using a 7/64” bit. The plug will usually twist out easily when the drill passes through it. Be careful not to enlarge the hole by drilling off center. When the plugs are removed use the same bit to drill out the passages. In most cases the rust and soot will come out with minimal effort. Now check to see that the float bowl air vent is clean. Finally, look into the throttle end of the carb and clean the two small idle jets with a small drill bit or wire. These jets are fed by the passages you just cleaned. Be careful not to make the holes larger. Now you can bead blast the carb body. Use electrical or heat duct tape to cover the name plate if it is to be left in place. Be careful not to use too much pressure on the brass float hinge as it may heat up and warp. Some restorers put the carb in a 1:3 dilution of molasses and water and let it soak for a week or so. The chemical reaction between the rust and the molasses reduces the rust to back
powder that can easily be removed with a tooth brush and toilet bowl cleaner. (Protect your skin and eyes from the caustic toilet bowl cleaner) Rince the carb body well with water when you are done. Carefully blow out all the passages with compressed air and check to make sure the old gaskets are removed from bosses. Make brass plugs by forming a round point on the end of the 1/8” brass rod and cutting pieces about 1/4” long. Tap the plugs into the holes and peen/rivet the end. This will expand the brass and seal the passageway.
1/8” brass rod can be purchased at most hobby supply stores. 17
Floats & Inlet Valves There are at least three styles of float valves currently available for use in the Holley NH. Each has its benefits and draw backs. The original “needle and seat” in like new condition works fine. The 1/8” inch orifice in this assembly is quite a bit bigger than the newer styles currently available for sale. Usually the needle has a ring worn around the taper and will not seat properly. This leads to a constant drip from the carb. Some enthusiasts who push their Ts to the limit like this style of valve because it doesn’t restrict the flow of fuel.
honed smooth using a drill press, some sand paper and a wood block. Cut one side of the block to a 30 degree angle. The taper on the needle is 60 degrees, 30 degrees per side. Glue or tape some 320 grit wet and dry sandpaper to the block. Chuck the needle in the drill press and set it at top speed. Squirt WD-40 on the paper as a lubricant. Now carefully dress the taper on the needle until the groove is removed. Finish the process with a finer grit paper, say 600 or higher.
Repairing the Original Needle
Replacements
The worn taper on these early style needles can be 18
New replacement needles have a Viton (synthetic rubber tip) that provides a pos-
itive seal. Some T owners complain that gasoline additives in some pump gas degrades the rubber and causes it to stick to the seat. The orifice in this setup is about 1/32” smaller than the original equipment. The Grose Jet or ball valve patented in the 60s by Ansel Grose does create
Typical wear pattern
a good seal. There is anecdotal evidence that some of these valves stick shut when the engine isn’t run for a period of time. Bits of debris from a dirty gas tank can also become lodged between the ball and the housing keeping the ball from moving and causing the valve to leak. “When you install one of these in the NH carb for the first time, you should have the fuel inlet elbow removed, and of course everything should be clean. Once the Grose Jet has been tightened down, look into the fuel inlet (where the elbow would connect). You should just be able to see a little bit of the end of the threads on the Grose jet. Look very carefully at the top of the threads. You are likely to see a whisper-thin whisker of brass that has been raised up at the end of the threads. This is likely happening because the end
After sanding with 400 grit
of the bore for the fuel inlet elbow might be a little rough in some carbs due to age, abuse, etc. Pick the brass shaving out with a fine tweezers. Don’t try to blow it out with air or wash it out with solvent because you won’t know where it ends up. The only problem I have experience with any of these valves is with an original worn needle leaking.” Adam Doleshal
So what is one to do? If the original needle appears to be in good shape tune it up and keep it. Remember that a gasket is needed to seal the seat in the carb body. Use a tiny bit of Loctite if you are concerned about the seat coming loose. When the seat is in place insert the needle and give it a couple of light taps with a small hammer to reform the seat. Install the needle and float and test the seal by tipping the carb upside down and sucking on the inlet. Seal the hole with your tongue. If the seal holds for about 15 seconds the needle should be good to go. Check for Leaky Float Before final installation check to see if the float leaks by submerging it in hot water. The heat from the water will expand the air in the float causing a tell-tale column of bubbles to stream from the perforation. New floats are available from the T vendors. The leak can be soldered but the heat from the soldering process may drive the air from the float with the solder sealing the vacuum inside. Atmospheric pressure will crush it when it cools. Clean the area around the hole with sandpaper or steal wool. Use thin, flux core soldering wire and a small soldering iron. The technique used to solder components to an electronic circuit board will work effectively for repairing a float. 19