I like my 1979 350 carb better than my 1972 455 carb. Both are 800's and were modified the same, but the 350 is more responsive and has adjustable APT. DAVID, the air bypass holes are in little ditches that empty under the front of the throttle valves. They are short, one is straight and the other has a short right angle. The gasket will not block these little ditches. With the right size holes and modified idle circuit, the air and fuel will mostly bypass the throttle and allow it to fully close or use no more than one turn in. My 1979 350 carb had NO HOLES drilled so I had to drill them to get idle. But,I only have 12 inches of vacuum. To all readers here. All 350 Q-jets become 455 Q-jets: if all the circuits and settings are modified to your 455 requirements. Most all Q-jets need mods anyway; same results in the end. MODIFY EVERYTHING AND I MEAN EVERYTHING. Will your carb idle with the throttle closed? (you probably got nozzle drizzel if you turned the screw in to open the throttle for idle). Does your secondary air valve open to at least 75 degrees? (Buick 455 is 80 stock) Is the air bypass drilled & to the right size into the two little ditches on the bottom of the throtle base plate? (more nozzle drizzel)etc.
I was wondering where i could purchase a 750 or 800 Q-jet for my 70 455? I just bought it and it came with a holley 750 double pump carb. It runs ok but i think it's a lil much. Can anyone help?
If I was looking for a Q-jet, I would call Cliff. http://www.cliffshighperformance.com/services.html Let him build one for your car
Well, I got in touch with Cliff and I am on the waiting list. I was tinkering this afternoon and saw that the choke thermostat cover is rusted and coming apart. Also, there is some oil around that area. I searched the forum but did not find much info. I also looked on oldbuickparts.com to see if there was a NOS part but no luck. Any ideas? Thanks Again, Dave
I also enlarged the holes that lead to the ditches. But where the passage winds up through the body to the air horn was blocked on one side by the gasket between the thottle body and carburetor body. Original gasket had both holes, new gasket in kit had only one. Not the gasket under the carb. Idle is good now with the throttle just cracked open, and the main jet kicks in right as the idle circuit stops functioning as the throttle is opened. Very crisp with no rich, or lean flat spot- very fuel injected feel as you describe even with TA413 cam. I'm running 24 degree timing at idle and 34" above 2200 RPM or so with 10 degree start retard for 14 while cranking.
