Your symptoms come from three common Pontiac and Rochester maladies. Any of the three can lead to that kind of behavior and usually they come two at a time.
Rochester Q-jets are notorious for running out of fuel at the top of each gear and about 100 feet short of the traps, particularly on bigger displacement motors like the 400, 428 and 455.
Great, thanks for all the tips/ideas/suggestions etc. There is a guy in Daytona Beach who has a shop right near Smokey's old shop. In fact, he and Smokey were friends and this guy is supposed to the "THE Q-jet King". I'm guessing he won't be cheap, but I am also guessing he could set me stright!
Make sure your fuel line from the pump to the carb is not resting on your water pump, or water passage in your intake. I like the vapor lock theory.
Cliff Ruggles book recommends modifications to prevent fuel starvation at higher rpms. I'm too far from home right now to look up what the book said though.
Maybe you should hide an electric fuel pump in the back?
Many people have suggested the electric fuel pump. This would be my absolute last resort. I've gone so out of my way to keep everything stock appearing, this would just not sit well with me... LOL
If that is a 74-76 carb then I would say that it isn't calibrated for your higher horsepower set-up. Things that I think Cliff Ruggles would suggest would be to #1 buy his book (probably the best $20 you will have spent in a while, #2 check float level, #3 fuel inlet seat size, #4 choke pull-off function, secondary air flap adjustment. If the carb needs a rebuild anyway, I would buy the book, get a kit of good parts from Cliff, and do it yourself. I did mine myself for my built 400 (400 horse est.) and 4 speed with a junk '79 Q-jet I bought for $20 on ebay. You can give Cliff the parameters of your engine and he can pretty much recommend jets, rods, secondary rods, etc. For instance, I was talking to him on the phone about ordering a new set of rods and main jets for my new motor and when he found out it was a '79 he suggested that I send him my secondary rods so he could mill them down to significantly richen up my secondaries, otherwise he thought the lean rods could melt the pistons. He knows his stuff and if you get him on the phone have your info ready and some time on your hands because he likes to talk! My car is a little scarey fast now (but I did have a tired 326 and an auto) Good Luck.
Definitely fuel. I heard a carb back fire. Sounds like secondaries. Think'n the air flap is opening to slow or to fast vs the trottle plate. Adjust the air flap "spring tension" and see what happens.
Originally Posted By 68 Firebird400
I am uploading one now where I start out in 1st gear, did a slight burn out, and you will see how the car falls flat and then recovers. This was the first time it ever did it in first gear and was the only time it did it tonight...
