I'm running Holley #6299 carbs which are 390 cfm vacuum secondaries. These carbs have been discontiuned for years but are still available on ebay. I'm running the vacuum tube balance kit-which made a huge difference. You also have to reverse the idle air circuit as these have reversed power valves. Holley still makes a 390 #8007 but it is an emmissions carb and there is too much JUNK hanging off it. I've talked with thousands of peoplpe of the years who are running tunnel rams. The general consensous was that Offenhauser probably had the best TR for the street. The plenum was smaller than other tr's and thye give the best driving response. The trick is not too run a big cam. The cam in my engine is very moderate and you want one that makes as much vacuum as possible to suck down that air/fuel misture. I'm also running the heaviest flywheel I could find (hayes 45#) to increase low end torque.
i ran one on the street for a 6 years ,454 about 475hp turbo 400 (2800 stall) 3:08 10 bolt in a 4010lb 56 suburban carryall,no drivability problems at all ,it had low bottom end torque but screamed on the top end. the truck ran 13.46 at 108mph in the quarter. i put a 3500 stall in and it ran even stronger but i never tried it at the strip. the key is not too big on carbs , i used a single 800 dp holley
Tunnel rams are no troubles whatsoever WHEN SET UP PROPERLY. I've ran tunnel rams on all sorts of stuff, from a daily driven work truck with a mild cam and stock converter that could spin the tires WHILE TOWING A CAR ON A TRAILER to a daily driven 440 Demon that passed AirCare emissions testing every year for 9 years without failure (NO detuning) Daily driven work truck, 5500+ pounds.... Demon that passed AirCare and was driven in the middle of winter with NO troubles whatsoever....
The Jalopy Journal
