Both of these carbs are pre-starter (one-arm choke, bronze body) but they differ in some ways.
A has what looks like a vent on the side above the bowl. That's not on B.
A is ¼" longer from end to end than B.
A has no flange on the choke end while B does.
Both needle valves have an oblong top. I've seen a drawing showing a round top, but I don't recall ever seeing one on an actual carburetor. Is the drawing wrong? If not, when did the needle valve change?
Anybody know the time line for these changes? The encyclopedia doesn't go into that kind of detail.
A ....looks like the mid-1914 Holley #6040 Model G., "Pat. appl for" The '15 was smooth inlet but marked "Pat. Dec 22, 1914".
B...seems with the grooved inlet is for 1916 and early 1917. Some were with and without groove.
Photos and more details in Gail Rodda's Vol. 1 Parts Guide.
Somehow I missed the Rodda reference. I think I will cheat and use the 16-17 version on my 1915. The flange on the inlet end will facilitate attaching an air filter.
Steve what is your opinion, Model G vs Holley NH.
No opinion. I haven't used the G yet. I've read that it's very good. I'll find out when I try it.
Steve, here is a picture of the round top. I don't know if it's correct or not. Most all the Pats Pending ones I see have the round top but this is a 1914 patented one. It was on it when I bought it, it has the smooth air horn. They usually have the oval top.
No knock Corey
I had a rebiult NH by Corey ran better then ny own NH
But in a whim put on a non rebiult brass G
What i noticed less sucking noise when choked and started 2 pulls not usual 6 to 7
Waiting on tires so i will do a road test with both but at present i say G i have far better then both NHs and i only used the NH on my past 19 model Ts and one Simmins
All where the hump back design
Again this no bad mark on the carb i got from Corey runs fine
I have run a Holley G for 10 years on my 15. They wildly outperform an NH climbing the mountains here in West Virginia.
Bought this NOS Holley G on ebay 10 years ago. With a wait on the side above the bowl.
With brass cup (which should be repaired any day), but it was cracked so I mounted this iron cup.