Weber 44 DNCF Grose Valve Jet

This particular valve jet has been around for years and has been used in racing applications. Production of these valves has been started. My intent is to start a discussion and generate interest in this now available jet. About two years ago a friend of mine told me about the Grose jets he had in his 44 DCNFs. He said they were worth their weight in gold. So as I went searching for them, they were no where to be found. Well, I guess so, they were out of production.

They are now being made. Why are these jets so much better than the Weber float valve AKA needle & seat?

What is and how does the Weber needle and seat [sometimes referred to as the carburetor float valve] compare with the Grose needle and seat [sometimes referred to as the Grose jet valve or Grose jet]?

The Weber seat is basically a hollow brass fitting that is cylindrical in shape. It screws into the underside of the Weber 44 DCNF carburetor top cover. It directly receives the fuel flow from the fuel rail. The needle resides inside the seat. The needle is also a cylindrical solid piece of brass that on one end has a spring-loaded ball bearing and the other end has a conical tip. The needle has three ridges spaced 33 degrees apart to not only center it in the seat, but to also offer the smallest surface area of friction and allow for the greatest flow rate of fuel, these are the sliding surfaces upon which the needle slides up and down on within the seat.

The conical end of the needle controls the rate of fuel flow into the fuel bowl. As the conical end of the needle is pushed further up into the bore of the seat, the area of the fuel inlet/opening is thereby narrowed, decreasing fuel flow. The other end rests against the float tab. The spring-loaded ball, acts as a shock absorber at the contact point of the tab. As the fuel in the bowl fills or decreases, the float will rise or fall accordingly, this in turn pushes the needle into the seat closing or opening the aperture of the bore in the seat proportionately to the fuel needs of the carburetor.

The problem with this arrangement is that over time a ring wear pattern develops on the conical end of the needle due to repeated contact with the seat. Once this happens, the seal between the seat and needle is compromised. In time there will be an ongoing leak into the fuel bowl as well as overall carburetor performance being adversely affected.

Enter Mr. Ansel B. Grose. Mr. Grose redesigned the needle seat arrangement. He used two ball bearings. The large ball bearing was in contact with the fuel float tab while the small ball bearing was in contact with the tapered bore of the seat. Since both bearings are constantly rotating, the mating surface of the smaller bearing never develops a wear pattern. The spherical face of the smaller bearing creates an optimal mating surface with the tapered bore of the seat. This in turn allows for consistent fuel metering, never develops a leak, allows for quicker fuel flow, and quicker fuel shut off [read improved throttle response].

This particular Grose jet valve will fit any Weber DCNF carburetor. The seat bore is 2mm and can flow anything up to a size 200 Weber jet and possibly more. Additionally, a 6-8 psi. fuel flow is no problem for the Grose jet valve.

These jets are on EBAy under Ferrari/Maserati.

I hope this starts some interesting discussions.

Ciao,
George

 

Correction - Weber 44 DCNF

Ciao,
George

 

Hi Russ,

I know there was a production run of these jets some time ago. The quality control was of a marginal degree. This is a new production run by a friend of mine. He is obsessive on quality when it comes to his Webers. They are eighteen dollars a piece plus shipping, IIRC. BTW I have three on order.

Yes, they screw directly into the top cover....no mods needed.

As you know these jets were made for all sorts of carburetors. So, I am guessing it was the SUs that had all the problems in the 70s. Anyway, machining has come a long way in the last ten years alone. I'll try to find the correct site to locate them. Try googling [Jims Garage - The Grose Jet].

All I can say is that they are easy enough to swap out and compare with the Weber needle & seat. As was told to me by another friend who runs these jets, the difference in throttle response/drivability is significantly better with the Grose. Only one way to find out.

Ciao,
George

 

Received my Grose valve jets today. They are very well finished, and are a direct screw in to the DCNF top cover. Such a simple and elegant design.

Regarding past failures; those were obviously inferior knock offs made who knows where. The only way the large bearing could ever be dislodged from the seat would be with the help of a sledge hammer.

I now can compare both the Weber and Grose side by side. The three cutouts for fuel flow in the Webers are significantly smaller than that of the 6 fuel holes in the Grose. Even more remarkable [to me anyway] is when I blow air through each jet, I get plenty of resistance from the Weber and virtually no resistance from the Grose. That must mean something in a high fuel flow demanding situation. The principle of the rotating bearings never developing a wear pattern is also most appealing. Consistent fuel metering and no leaking from the seat bore....whats to not like.

I suppose in day to day boulevard driving, the Weber vs the Grose difference would be impercievable. However, under demanding driving conditions such as spirited mountain driving or track driving, I believe you would notice the difference quite readily.

That's my story, and I'm sticking to it.

Ciao,
George

 

What exactly would you like to see, Russ?

Ciao,
George

 

By rough measurement it looks like the Weber needle has 9mm of travel. That seems consistent with the 48mm - 58mm float setting. The first 5 mm of movement of the needle is no fuel flow - full fuel flow. The Grose valve jet in contrast has 2 mm of movement for the full fuel flow range.

Dimensionally, the two look the same in proportion.

As far as the float goes, it looks as though it will keep the fuel bowl consistently full. It wil be in the 50mm - 48mm range I believe.

I'll try to post some pictures tomorrow.

Ciao,
George

 

For information about the Grose Valve Jet you can contact John at:

[email protected]<mailto:[email protected]>

Ciao,
George

 

It will be a while before the road test, so don't hold your breath. One more carb to go, and then the intake manifold comes out for honing and polishing the runner interiors, followed by an exterior thermal ceramic coat.

Ciao,
George

 

The Grose valve jet in the top cover. The second picture compares the Grose with Weber. The pictures are fuzzy but you can get a good idea of the dimensions.

Ciao,
George
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Extrude hone is a whole new topic...in some cases it is good, in others not. I will start a thread on the manifold when I get started, in the Maserati Merak section of course. For the time being Russ, the answer is no. I will use grinding compound with a honing tool attached to a variable speed drill. I will final polish it with Mother's Metal Polish. Should feel like glass when I finish.

Ciao,
George