I don't want to highjack the Speedster Carb thread, but it did make me wonder about something. Say Billy Bob was building his T speedster back in 1920 something and decided he wanted to try a dual carb set-up. Billy Bob is on a budget, but he has a few NH's laying around. What kind of problems would he encounter?
It's been done. The usual stuff like balance and having a "log" type manifold to equalize vacuum between the two carbs.
Dual carburetor setups were very rare in-the-day . Most average people just went to the wrecking yard for a bigger carb , and adapted it somehow . The rich , or more dedicated , unmarried , Speed Demons bought the Hot single carburetor-and-manifold sets . Unmarried because speed costs money , how fast do you want to spend , and wages were too low for most people to support a speedster AND a wife . A Winfield carb-and-manifold setup might cost 2-to-3 weeks wages for the average young man in his 20`s then , without leaving any money to eat or pay rent . Taxes were not a big item for average people in the `teens and `twenties .
Gee and I thought when you ask about l carbs you were talking about noodles and spuds.
Dual carbs are at the mercy of small valves and little ports! That is the main reason they were not used.
Small ports and valves , yes , but also because balancing dual carburetors was a black art then: few people knew how .
A good friend who doesn't usually hit the forum runs dual NH carbs on homemade stub manifolds. No log manifold or crossover pipe. The car has a Z head, Stipe 280 cam, and an A crank. I don't recall what he uses for exhaust, but it's either the dual from Chaffin or a Model A, a bit more open than stock. He hasn't seemed to have had any problems setting the carbs up or keeping them balanced. He opened the intake ports a little too but nothing exotic. The car idles well and runs very nicely.
I put a post on the "Carbeurator choices for a speedster" thread before I discovered this thread. My posting is more appropriate for this one, so here it is again. Also, the fellow that Walt is referring to has the exact engine mods that I do, with the exception of choice of carb.
Here's my setup. I run twin Walbro WHC's as sold by Texas T Parts. The manifold is a home built setup with no crossover. Once the carbs are sync'd they seem to stay in sync until I do something to mess things up. Adjustments are done in very small increments as just a little change in setting seems to make a big difference. I really like the low speed and high speed adjustment capability of these carbs. The drawback to these carbs is that I get alot of ribbing from some of the other speedster guys about stealing carbs from lawnmowers & such.
If the split intake were machined out to except much more area for air to enter it would be intersting. NH carbs are very old story. Mikuni carbs have seven overlaping atomizing adjustments and a varable venturi even one would be several times more then an NH. Ride a Harley with the proper Mikuni setup, the differance is shocking over stock.
Here is a shot of dual MH's I saw in Richmond in 2008.