I'm in the process of setting up a 455 for a 4x4 Pickup. It's using a TH350, so I need the linkage for the cable. Here's the combo of parts I have: '74 Electra Q-jet # 7044240, has what I believe to be the original #70 jets, 40 rods, with CT secondaries. '81 GMC Q-jet # 17081226, has 72 jets, 50M rods, with DR secondaries. The '74 carb sat for quite a while, it's full of white powdery residue(the jets are actually plugged), and frankly, I don't know how much I trust it cleaning up well. I'm leaning heavily towards trying to use the '81 carb. It was a runner up 'til the gutless motor under it puked. It looked showroom clean inside when I opened it to check the jet & rod sizes. I can add a spacer to get the clearance I need to the manifold, then all the linkages are right for the truck, and I gain the electric choke. That's the simple part. I know I can't just swap the '74 jets & rods into the '81 because of at least the pre/post '74 thing. From what I've seen the idle air bleeds probably need help. I just got off Amazon from ordering Cliff's book, but can someone chime in with a little heads-up on what I'm getting into? I know I can get my hands on a '79 Buick 350 Carb and probably a few more 455 carbs (2 being 75 or 76's), but I don't know they'd be in any better shape than my '74. As far as what the truck will be used for, it'll be mostly standard homeowner stuff; hauling lumber & landscape materials, trips to the dump, etc., with occasional duty pulling a car trailer. For me that all means Interstate and highway use to get to those places, and it's geared accordingly. It was special-ordered with 2.73's that might still be in there and has 32" rubber. It runs just over 2000rpm around 60. I don't see me ever taking it over 4500rpm. Thanks
If the truck was a 350, you're adding 100 cubes which require more idle/transfer fuel. The addition of ethenol in today's gas also requires a richer idle/transfer circuit. I would talk to cliff ruggles and get a complete overhaul kit. Remember to get new idle tubes. Read the book for tips and setup. Make sure all the gasket surfaces are flat!!! The only drawback may be the fuel inlet being different on a chevy vs buick. Good luck
dont know too much specifically on the 455 yet.....someday it will be mine,have a lark with a 350 currently,but would suggest buying an aftermarket carb,i am sure someone here if cost is a concern has something used or knows where to point you, to at least get you something matching a pre 1972 tune and with performance in mind not sure how stout your trans is built for that matter,but in general,the further you get into the 70s the more restricted horsepower and more importantly torque were,and if its ever has to go offroading,or at least built with that as a consideration even just to get to tough jobsites, a newer style carb with a reliable electric choke system is something you would probably want, especially for steep grades and changes in elevation,or just starting it again without at least spending 5 dollars a keyturn,if youve left it in a foot of snow while your out hunting snowmobiling,etc.........or it just gets cold some mornings
The 800 CFM Q-Jet core I just picked up (7042240) has 48B primary rods, 72 jets, and CT secondary rods. The CT rods are much more blunt than the AY rods I have in my 67-issue 430 Q-jets, so there's much less fuel delivery to the secondary bores. I'm going to try bumping the primary rods down to 45Bs, and keep the 72 jets, and try a set of AY or AU rods in the secondaries. For your purposes, if the engine has all the smog stuff hooked up, then use the newer Q-Jets. Otherwise, just rebuild your 7044240 with the bushing kit and pump kit improvements, and try to keep the rod/jet combos within 10% of factory specs.
I thought about just using the '74 carb, but I don't know that I trust it, And to use it I still have to either swap the baseplate or at least the linkages. Then add a spacer to clear the kickdown cable, which means I need to make a new longer rod for the divorced choke. Neither is difficult. I just don't know that it'll come clean enough internally to work right whereas my '81 750 looks new inside. If I can just change rods/jets, it seems the better way to go. Post # 455!! That's like a Golden Birthday! There should be presents or something for that one.
The '81 CCC carb isnt neccisarily a bad choice - talk to Ken at Everyday Performance (in the vendor section) he knows how to make them run with some recalibration.
look down the primary side , the one with the bigger hole is the one u want. a 455 needs at least 800cfm. tear it appart, dip it overnight in the can o dip. Actually it wont fit in the can u have to pour it into something that it will fit in.
