Does anyone know the CFM ratings, Jet sizes and metering rod set ups for the Buick 350 and 455 Quadrajets from 1970-1972? Also I have a 1970 Hi Compression 350 that has an upgraded ignition and Headers that I am thinking of putting a 455 carb on just not sure what CFM Q-Jet to go with. Think this would be to much gas for the 350 to handle? Thanks
That answer can turn out to be a long one. In general terms, Q-jets were 750 cfm for both the 350 & 455 engines in '70. '71 & later saw the 455 get 800 cfm, the 350 remaining at 750.
Your original 1970 Buick 350 q-jet was 750 cfm and used a .069 jet and 45B metering rod. Secondary rod was a BS. A 455 Q-jet may work OK without changes if the jets are close. Example,the 1970 455 was also a 750cfm and had .067 jets and 42B rods (SMALLER !) I have an 800 Q-jet from a 1979 350 Buick and it has .073 jets and 48K rods. The largest jet for an 800 carb will be the 1971 455 STG 1 which had .075 jets and 45B rods (.045") with AU rods in the rear. The standard 1971 455 had .073 jets and 44B rods and would probably work fine on a 350 Buick. *800 carbs will have larger jets than 750's, to match larger venturis. *1975 and up takes "K" not a "B" rods (different lengths-NO INTERCHANGE) *I think Buick switched 350 engines to 800 carbs around 1975. *The many little holes, tubes and such inside the Q-jet are sized to match the engine. Big block carbs will work OK on a 350 better than small block carbs on 455's. Hope this helps. Gary B.
Like stated above its the idle circuit air flow that differs between the 455 and 350 carbs and it is correct that the later 350 carbs are 800 cfm and work great. I've been using both stock and re-jetted 455 71-74 carbs on my 350s from mild to cammed out nitrous engines with great results.
Each year had many different applications for different engine/trans combos so jets and metering rods were always different. For instance a 455 carb may be different for a base auto trans and different. for a 4 speed and different for a stage-1. You have to know what you want. 71-72 Stage-1 carbs came with 75 jets 45B metering rods and AU secondary rods. The same primary rods and jets in a 70 carb would flood it.
So would there be any noticable difference in performance between a 71 455 auto carb and a 71 455 stage 1 carb on either a 350 or 455 engine?
Depends on the engine. The Stage1 carb is jetted richer. If the engine wanted richer, maybe. Kind of hard to answer that question. Why do you ask?
A hot 350 might like a 455 carb. Why not try it. See if you can feel any more power. You may be able to use a 455 carb on a 350, but the reverse is definitely not recommended.
