Join Date: Jun 2012
Location: Aurora Colorado
I have been running many different types of carbs for the last 30 years. I have become a big fan of the annular booster carbs from quickfuel. (they are an upscale holley type carb) The annular boosters which were what was in the autolite 4100, are also in the summit carbs, and some demon carbs work very well at taming the rich idle produced by lopey low vacuum performance cams. The annular boosters atomize the fuel better with a lower vacuum signal and on my motors produce a much crisper throttle response than any edelbrock, carter, or downleg booster standard type holley ever produced even when tuned perfectly with an afr meter attached.
You pay a little more for a good quickfuel annular ( about $550 for an ss model) but as you come to find out over the years in performance equipment you usually get what you pay for.
Someone suggested pro systems for a carb also. They will ask for your engine specs and send you a carb that will be almost spot on out of the box for your motor with jetting and power valve, but will probably cost more than the annular quickfuel which you can easily tune yourself. If you have the cash pro systems is an excellent choice.
Also I will share my carb sizing findings from my 331 that was built by Keith Craft. It was super mild with only afr 165 heads, 10.4 compression, regular rpm edelbrock intake, jba mid length 1 5/8 headers, 2.5 inch exhaust and a tiny crower cam ( grind # 15510) with only 212deg @ .050 and 275deg adv. with .531 lift on a 114 lsa. This cam is suggested as a good idle stock 5.0 HO replacement cam in a 302 not for a 331!! But I wanted a smooth idle and lots of low end tq.(It idled like a stock 5.0 at 650 rpm when warmed up). The carb was a 600 holley dp set up and tuned by Keith when he dynoed and tuned the motor. The dyno results showed that the carb was a significant restriction from being too small from 5200 rpm up. I was the one who specd the tiny cam, heads, and carb.... Keith would have gone afr 185, larger cam and 750 carb. I still would have had great idle quality and an extra 50-60 hp. (it dynoed 386 hp/405tq at the flywheel with my crappy cam/heads/carb)
The moral of my expensive underpowered stroker build for your motor is simple. On a 347 you need a 750 carb since my mild 331 showed a 600 was way too small for it on a dyno tune.
I did correct my errors on my 331 before I sold the 65 fastback it was in. I replaced the heads with afr competition ported 185's, installed an fti cam from ed curtis, a vic jr intake, 750 quickfuel annular, 1 5/8 hooker longtubes with full 3 inch exhaust. The car still idled good had a nasty performance growl out of the exhaust and you needed a neck brace on when you hammered the throttle in it.