As the title asks. I have read the '71-'74's are 850cfm which might make a decent size for a big block. I feel the 800 is a bit small for a Big block. Almost small block Chevy article doing an engine build uses a 750CFM carb. I realize they rev more than the 5500rpm that most BBB's see but honestly is an 800 enough? I remember Jim bell recommending doubling the engine's cubes to determine the carb size needed. Granted at the time he was selling the T-Quads and I bought an 850 for my 401 nailhead. he of course recommended the 1000CFM for the 455's assuming some mods were done. What is the current thinking on this subject? I always liked a spreadbore and with a fresh one got 19mpg on a 1970 455 GS I took on my honeymoon(Q-jet, new for a '70 455 GS). Thanks
There were some 850 cfm quadrajets produced without the outer booster rings in the primary side. They are very rare and have a very high selling price. The 800 cfm quadrajet does very well on applications up to 600 hp, and does a great job with a combination of fuel economy and performance.
Edelbrock made an 850 q-jet. I had one and liked it. But I like Holley's more. p Not smart enough to tune a q-jet.
after talking to some dyno operators the carb rating isn't carved in stone, a strong motor will pull 785-800cfm from a 750cfm rated carb, it probably requires a lot of testing and tuning to hit the sweet spot for a certain combination. many dyno'd engines require adjustments at the track depending on conditions. unfortunately this involved testing requires cubic dollars.
That was the #1910 PerformerRPM, it had primaries like the 71-74 800com Buick. It was not a single primary booster carb like the Pontiacs. Real good carb, flows a lot of fuel, .149 needl e and seat
The Edelbrock 1910 was patterned DIRECTLY from a 1980 Chevy truck unit, part number 17080212/213. There is nothing special about them, and they are the exact same castings. The only thing done to them to increase cfm over the truck carb was to shorten the stop of the secondaries so the flaps opened a wee bit further. Otherwise, there is nothing "special" about a 1910 over any other late model single main airbleed Chevy q-jet. IF they really flow 850cfm, then ALL larger primary bore q-jets set up the same way will do the same thing. Pontiac made 827cfm q-jets, there were a one year only design, lacking the outer booster rings on the primary side, and use on the Pontiac 455HO engines in 1971. Buick as the only large "800" q-jets that were divorced choke, used on all the 455's from 1971 to 1974. Pontiac Super Duty 455 carburetors are also the large castings, made in 1973 and 1974 and were hot-air choke. All front inlet late style q-jets from 1975 to 1980 will also be the bigger castings. Side inlet Chevy carbs cam in both small and large primary bore models from 1975 to 1980. The SMAB Chevy models are going to be the larger castings, with two exceptions, the divorced choke Truck carbs use in 1977 and 1978. Quite a few years ago we had several carbs flow tested, a later model front inlet carb set-up like a 1910, and another one with the our booster rings removed. They flowed 847cfm and 897cfm respectively....Hope this helps some.......Cliff
There's one on ebay if you're still interested. http://www.ebay.com/itm/850-cfm-ROC...910-/331582178749?hash=item4d33d685bd&vxp=mtr
I would like to clarify a point on the '71s from 455s. Are they all 800 CFM? Not trying to call anyone out, but there are comments out there on the interwebs that might lead one to believe that some '71s are not.
All of the 71 Buick 455 carbs I have worked with through the years are the large casting 800 Cfm. All of the 71-76 Buick 455 quadrajets were large castings.
