intrested to hear differences between a 350 and 455 quadrajet. I have 2 nice 350 cores. One oem 350. 1970 gs carb. One replacement. From poston long ago.
What year 350? What year 455? What brand of 350? What brand of 455? There's more friggin' differences among the Q-Jets than you can shake a stick at. Air bleed sizes and locations, jet and metering rod differences, idle air bypass--or not, pullover enrichment--or not, Divorced, hot air or electric choke. Choke lock-out on the throttles or on the air valves. Front, rear, or both choke pulloffs. 750 vs. 800 cfm. And there's plenty more beyond that. I suppose we could expect the 455 to have more idle fuel available.
As Schurkey mentioned, almost all codes are different calibrations. If you take a 70 Buick 350 7040244 and compare to 7040240 for the 455 you would find differences in the following Jets Primary rods Secondary rods Idle bypass air Idle tubes Down channel restiction Upper idle air bleeds Upper main air bleeds. Go to 71 and the 455 carb is 800 cfm while 350 is 750 cfm
Assuming the carbs are from the same year, just calibration till 71. After 71 the BBB carbs flowed more air, and were calibrated different because of it. JW
I just want to point to a smaller engine quadrajet can be modified to work right on a big engine like a 455, this work should be done by somebody who really knows how the fine adjustments on the quadrajet works and procedures like removing the idle tubes can be a lot tricky but it can be done for sure
I find a stock 800cfm 455 carb (71-74) works great on a stock or mildly modified 350. Idles better due to a bit more fuel and air. Might have to tighten secondary air valve a bit. It essentially become a pre-emission carb when put on a 350.
For a 455, 9.3/1, performer, 1 7/8 headers, bowl ported small valve, 278 comp extreme energy cam. Makes about 400 hp 13" vacuum. 7042944 KH 0032. My best core. Tho died at etown and legged it home. Bought new from poston many moons ago. 1 stock rebuild. 7043240 LA 0253, been thru a few hands locally and , lost accel pump regularly. Some internal mods only made things worse. I gave up on it. 7044240 KA 2493. Bought built for sngine was good but eventually puddled intake. Main body is very porous looking at wells. Retired this too. 7040244 KA 3099. Oem 70 gs350 auto carb. Needs complete rebuild. In box of my 7042944.
Technically, any Quadrajet can be calibrated and set up to run on any engine. We prefer to start with a same make and engine size carb when possible to modify from, but it isn't necessary. That being said. If you aren't going to use the 3240 or 4240 (both 800 cfm), then you can set up the 2944 or 0244. I would use the 2944 for the different seal on the inlet. You will need to create idle bypass air in base and possibly main body, plus the idle tubes, DCR's, jets, primary rods and secondary rods. We sell a re-calibration kit, which includes all the items needed to build the carb, and calibrate for any specific application. Only thing it doesn't include is the secondary rods. Cliff also creates custom kits for specific application. https://quadrajetpower.com/qb3-ez-recalibration-kit/
