Howdy Back CC and All:
We've been using the Autolite 2100 two barrels for quite some time now. We got turned onto adapting them from an old Hot Rod article series in which Ak Miller went after the, then new, Mustang Six. He modified the intake log, by milling off the stock one barrel carb mount, oblonging the hole, tapping an aluminum plate and mounting it to the log, then mounting the carb onto the plate. Add a cable linkage and a V8 air cleaner and tune to your tastes.
This is a much better option than a larger one barrel. Two smaller venturis give much better fuel atomization and a stromger vacuum signal, for better idle, transitions and a two barrel has more cfm for WOT. It is no longer stock appearing though.
This has been covered before, but to recap, the Autolite 2100 is a cost saving Autolite/Motorcraft/FoMoCo clone of the Holley 2300. They are no longer available new, but are easily obtainable in the recycle yards and rebuild kits are cheap. They were used on a jillion FoMoCo cars and trucks in the 60s, 70s and early 80s. They are available in the rebuilt/remanufactured market and, typically, much cheaper then Holleys. Some Holley parts interchange; Power valve and electic choke, but, unfortunately, not jets.
The pluses of the 2100 Autolite over the 2300 Holley are annular discharge venturi boosters for better idle and transition, dual bowl vents, no gasket seams below the fuel level, and they come in eight different sizes ranging from 190 cfm to 424 cfm. We're currently using 1.08 venturis on Dennis' hot 200 and my 250. The 1.08s flow 287 CFM and seem about right for most 200 applications. I have a 1.21 that I'm going to try next summer on my 250. It is rated at 351 cfm. These ratings are at 1 and 2 barrel standards at .3 of an inch of pressure.
I believe Holley two barrels carbs are rated at 4 barrel standards at .1 of an inch of pressure drop. To be comparable a Holley 350 would be rated at 250 cfm, and the 500 at 357cfm, which puts them right in the ball park for use on our 200/250 sixes.
I don't mean to imply that Autolites are better than Holleys. Holleys are great, I've got several. I love them. They are very tuneable. They are available new and any speed/parts store has parts for them. Doug's set-up looks awesome.
Both brands suffer from an application specific idle circuit range. If the idle screw adjustment is in the range of your application great, but if not, you must go inside, through sealed caps to open up the idle restriction channel and then reseal the opening. It is a scary, trial and error proposition.
Clifford and some other Co. make and market funnel adaptors for mounting these carbs on a stock log. Be sure to specify your carb hole size when ordering. Adaptors do cause a hood clearance concern.
Adios, David
