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I have a edlebrock 800 4 barrel carb on a 350 small block 1975.
I don't know why, but I would guess 2 weeks ago, my 4 barrel stopped opening up.
The engine was rebuilt recently, the engine is working great, what could have caused this?
If the choke plate doesn't fully open, because of the choke spring not fully opening, the secondaries will be locked out- exhaust gas routing problem. Other cause could be that the throttle cable was moved forward in it's holder, or not installed correctly to get a full pull on the carb.
i am guessing edelbrock spread bore? could it be because the 800 cfm carb on a 350 is so huge that the engine doesnt need that much air, vac secondaries are demand only. if the engine doesnt need it, the valves wont open.
plus, how do you know they arent opening. did you do the paperclip trick or something similiar like can be done with a holley. a properly working vacuum secondary carb should transition into the 4bbl so smoothly that you wont notice.
Did you install some new floormats? ...insulation under the carpeting? If the throttle cable/linkage extends the throttle to full-travel on the carb when your foot is "to the floor", then you have a mechanical problem with the linkage/actuation mechanism on the carb. If it does not open the throttle completely, adjust the throttle linkage and/or the cable adjustment on the accelerator pedal.