Cliff, you are probably getting tired of me popping in and out of here. Tonight on my 1970 455 GTO I put the original F hanger and rods as delivered from Cliff's HP. I also finally got the exhaust set up to use my wideband LM-1 tuner. First thing I did was warmed it up, went out and hammered it while glancing at the AFR meter. I notice a good dip in the AFR to the 10s (with slight stumble with almost 1 full turn on my secondary air valve spring) and as the secondaries fully open my AFR gravitates toward the high 13's low 14's (too lean for WOT). With the secondary setup from my Firebird installed which has a B hanger and richer metering rods, I literally felt and heard the difference in performance. I must get a richer setup for this car, but I continue to struggle with quick WOT stumble. It seems that this cannot be a lean stumble and I do see a puff of black smoke immediately after the stumble event.
I now have two cars that seem to experience a power dip on application of WOT (stock GTO 455 with slight stumble, and 1968 Firebird which has a short power dip I can feel at WOT). Could my 5K altitude upset a perfectly well behaved pump shot that works great around sea level. Also, I have moved both accelerator levers to the outer hole to reduce the shot, but I still have these issues. Before questions arise about the carb build itself, Cliff built them both for me based on the specs I gave him. I am running out of ideas unfortunately.
Cliff, first off would it be possible to get a richer set of metering rods and/or shorter hanger from you for my 1970 GTO since it seemed to really like that and the data seems to back my seat of the pants and ears experience.
