Ihave a 10 1/4 455, ported stage 1 heads, 290-08H cam, stock rockers, ported performer, headers, 3000 converter, 373 gears 275-60-15 radials or same size wrinkle slicks and an old Q-Jet set up for KB 118 cam. My Idle quality is poor, off idle it seems to run good {fresh motor so I havent run it to hard} should I modify my Q-Jet {if so how?} or get into an aftermarket carb {If so which one?} I almost ordered a Demon but I couldnt decide which one. The car is a 71 GS. The goal is getting thrown off K.C.I.R for running better than 12.00 without a rollbar. Any help getting me there would be gr eatly appreciated. Thanks Lin
You need your carb to match your engine set-up. Idle quality is poor due to low vacuum. Power piston spring will need to be changed. Best bet, contact John Osborne or similar carb rebuilder. Tell them your engine and car set-up specs. Also, you will need to buy some new rear tires once you get the carb back from them and on the car! :3gears:
Actually, you will likely find that the Q jet is the better of the two carbs anytime it is compared to another carb, due to the venturis utilized in the Qjet. Since they are high boost venturis, they will react better than most other carbs to changes in air flow. If the engine runs well now, keep what you have. Note the idle mixture procedure elsewhere in the forum, and if necessary, I can outline the changes needed to various circuits to allow better use of the cam. Ray
Thanks Guys Im glad to hear a Q-Jet can be up to the task! I have already cut 3 coils out of the primary spring {didnt change anything} and have read you can drill out the idle tubes from .031-.049 but if you go to much for your combo there is no going back. My current carb is #7041540 Ive heard that is the one to have. But I have a #7043240 off a 73 455. If the 73 carb would work as well as the #7041540 I could keep driving the car, and keep it for a milder engine. I guess I should find John Osborne and ask him. If the needed mods for my combo are clear cut and basicly straight forward, Im pretty good at monkey see monkey do. But paying a pro would be good piece of mind, and gotta be cheaper than a demon. Thanks Lin p.s. Took it to be inspected today, when I picked it up a croud had gathered around it, as I walked up one guy said Im not sure what it is but you should have heard it when the mechanic pulled it out. I listened to them until my 7yr old told them it was his. Now another group of guys know what a GS is and what it can do to radials.
