MTFCA Forum

26 Tudor with Holley NH carburetor.

It has the modern style shut off instead of the typical needle valve shut off. Other than the casting all components are new. I have checked float level and its where it should be and will shut off when I raise the float manually. Is there something I'm over looking or is this a norm when parked on a slight grade? I plan to adjust float height so it can shut fuel flow off at a lower level in the carburetor bowl as a solution.

Carburetors in Improved Fords typically came with larger, more buoyant floats because of the increased head pressure available in those cars. Carbs rarely are rebuilt with that correct float. It helps quite a bit.
Do NOT lower the level of fuel in the bowl as that will completely screw up the mixture control. NH's are extremely simple carbs but rely on this one setting to be correct. Your car is running off of the idle circuit up to about 20 MPH before pressure differential is sufficiently high for the main jet to take over. Both require the fuel level to be perfect in order to operate at low RPM and high RPM on the same richness setting. Those folks who either love to play with or MUST play with their mixture control while driving simply have maladjusted carbs.

If your "modern" shut off is a Grose Valve, well good luck. Dripping or sticking shut, or both are unintended features of that valve.

It should not leak, even if it is parked with the fuel shut off left on. If it leaks with the fuel shut off closed, it suggests that both the float needle and the shut off are leaky, OR, it might have s light leak at the fuel pipe connection at the carburetor. That could allow it to leak the fuel in the line out even if there is no problem with the shut off or the float needle. The fact that it leaks when parked on a slope might point to a bowl gasket issue or a float level issue.

When you pull the bowl, check that the float cant hang up on the bowl or carb center in addition to fuel level setting. Fuel level & float setting distance may not necessarily be the same. A looser than necessary float/carb hinge can cause.

What angle? Is it high in front or in back, or does it lean toward the right or toward the left? And, does it not leak on level?
If the car leans toward the right, the bowl level would be lower at the left and possibly cause the float to drop. That would allow some fuel to fill, however unless it leans very much and or the bowl gasket is leaking, it shouldn't run out. Likewise if it leans in any other direction, if the gasket leaks, some fuel could spill. It could also be caused by the float sticking on the edge of the bowl when it is on an angle.
Norm

Thanks for the quick replies and her is more information based on questions received;

1. Front end angle of incline is 5-8 degrees. Vehicle is not leaning and forcing it to either side doesn't impact the leakage flow. The fuel is coming from a hole on the back side of the casting just above the flange the fuel bowl seats on. Regardless of gallons of fuel in the tank it has leaked.
2. It has the latest float and it moves freely. I may need to go back to a needle valve shut off versus the modern ball valve type.
3. There is a inline fuel filter to catch debris.

As for running on the road I'm see speeds up to 35 mph on flat roads , not gone up any steep grades yet.

That sounds like a float needle/seat or float sticking/leaking problem. The carburetor should not leak even if you leave the fuel shut off ON* when parked. (*Not a good practice) There is a vent hole in the casting where you described your leak. It sould have a small brass tag over it, but not sealing it. If gas leaks out there, you have an issue with the float/needle/seat.

radiatorman wrote: ↑

Mon Oct 04, 2021 12:08 pm

Thanks for the quick replies and her is more information based on questions received;

1. Front end angle of incline is 5-8 degrees. Vehicle is not leaning and forcing it to either side doesn't impact the leakage flow. The fuel is coming from a hole on the back side of the casting just above the flange the fuel bowl seats on. Regardless of gallons of fuel in the tank it has leaked.
2. It has the latest float and it moves freely. I may need to go back to a needle valve shut off versus the modern ball valve type.
3. There is a inline fuel filter to catch debris.

As for running on the road I'm see speeds up to 35 mph on flat roads , not gone up any steep grades yet.

Sounds like internal needle & seat is not sealing. You dont mention type. Viaton, gross, original or other. Viaton works best. When working properly you dont need an external fuel shut off. The external fuel valve is obviously not shutting off 100%.

If you have a Grose Jet get rid of it and install a viton tip needle.

I have had no luck with the grose jet ball type valve. One car I had one on would run out of gas when under load. Replaced with a viton needle and no more problems.
Norm

Dwight

your factory sediment bowl has, or should have a screen. If that is intact, as it should be, it will filter out anything that matters to an NH. An NH carb will digest anything smaller. All membrane-type filters eventually clog, and you will most certainly break down or run poorly. If you do not believe in the efficacy of the original screen in the sediment bowl and just HAVE to have an additional filter, then you would be well served to install a clear sediment bowl with screen (strainer) immediately prior to the carb rather than an actual filter.

If you find that your car bucks or overheats on long hard pulls, it will be due to the Grose valve and/or filter starving your car for fuel and running too lean. Neither allow very good sustained flow under heavy throttle.

I have the gross valve like what is shown in the picture. Going back to standard needle valve with Viton tip. Thanks for all the responses.

Why do the vendors continue to sell these ball valve/gross jet. They are useless in a gravity system.

radiatorman wrote: ↑

Mon Oct 04, 2021 2:20 pm

I have the gross valve like what is shown in the picture. Going back to standard needle valve with Viton tip. Thanks for all the responses.

96092 gross valve.jpg

Remember, the viaton as purchased wont flow as much fuel as the originals. You could experience leanness @ highest demand (hill climbing) unless modified. Unmodified they still seem to flow more fuel than the gross.

There actually is a Viton-tipped valve which has the correct through-put. It was featured by Dan Treace in the latest issue of the MTFCA magazine.

Does the Holley NH viton tipped needle valve work in the same seat as the steel needle valve?

In other words are both needle valve seats the same?

My steel needle valve is leaking through the air/choke opening when parked and engine off.

I trashed the gross jet valve.

topkick7 wrote: ↑

Mon Jun 06, 2022 5:15 pm

Does the Holley NH viton tipped needle valve work in the same seat as the steel needle valve?

In other words are both needle valve seats the same?

My steel needle valve is leaking through the air/choke opening when parked and engine off.

I trashed the gross jet valve.

This situation recently came up @ out Thursday night T party. A guy was complaining a new viaton needle was leaking. A quick look @ his carb showed he put the viaton needle in a stock seat. The stock seat inner body is larger than the viaton unit. The viaton needle fit way too sloppy.
So, no, the seat bodies are not interchangeable.

I've had a Grose Jet in my carb for many years. I guess it's one of the few that work okay. That said, I'd never use another one or encourage anyone else to do so. In a carb I'm currently rebuilding, I'm going to use a "full flow" valve, made by Scott Conger.

Quote from Scott's post: Those folks who either love to play with or MUST play with their mixture control while driving simply have maladjusted carbs.

When I'm asked (seldom tho) about carb/fuel issues the one thing I emphatically emphasize is to get your carb mixture set to where your car "likes it" and then leave the dang thing alone!! I rarely ever, enough to say even never, touch mine and I have no starting issues, no running issues.

Here Here Tim ! I agree completely.

Allan from down under.

Like Jerry says, get Scott’s full flow needle/seat and be a happy camper from now on! No more running out of gas on hills with a reasonable amount of gas in the tank!

Maybe I'm just hung up on the belief that I have a constitutional & GOD given right to seek out the the best possible air/fuel ratio in order to
get the best performance I can out of Henrie's 20 horse power wonder. But I find it hard to believe that the same carb setting @ sea level
will work just fine @ 7000 ft. above sea level? The same goe's for timing & RPM.
Your results may vary.
Craig.

Forgive me Craig for I have failed to take into account the vagaries of altitude, climate and topography. In South Australia we can drive from sea level to just over 2000'. Our climate is just like southern California, without any snow due to altitude, and a good model T will rarely need to use bottom gear on the few hills we do have. I have seven model T's, and I never need to fiddle with the carburettor settings once set.

Allan from down under.