Next, you said you added a collector to the headers, so we're assuming you're running this engine at the track uncorked. Collector extensions are an excellent way to add torque at low speeds, but they really work best with camshafts with lots of overlap. Your combination is already advanced 2 degrees, and the Edelbrock RPM cam is not that radical at 224/234 degrees of duration with 0.050-inch tappet lift and 0.496/0.520-inch valve lift. However, the collector extensions should still help torque. You say that the car slowed down, but again it could be because the air/fuel ratio was dead rich. Perhaps with the collector extensions, the air/fuel ratio needed to be leaner. There's also the question of atmospheric conditions. It sounds like these changes occurred over several trips to the track. If the air was getting progressively warmer each time you drove at the track, it would also affect your times. It's not unusual for the warmer air with higher humidity and lower pressure to slow a car down by 0.30 second. If you did not keep track of the conditions, this is a huge variable. Plus, warmer air temperature combined with lower pressure and more humidity require you to lean the engine out, but it appears that you went richer instead. It's not surprising that the car slowed down.
'CC Quickies
Black And White
The photo in This Guy's Garage shows the GeeTO Tiger in black and gold-but wait, this one has white paint. Are there two cars? No. Back in 1966, there were two cars, one white and gold, the other black and gold. For the re-creation, this car is half and half.>>>
Here is my suggestion. First, figure out what happened to the Q-jet that caused the idle problems. It might be something as simple as a little dirt in one of the idle-mixture circuits that a disassembly, cleaning, and shot of compressed air and new gaskets will probably fix. Then see if the car returns to its previous performance. If it does, you know that the Holley was probably too rich. If you want to try to make the Holley work, put the power valve back in, put the stock accelerator pump back in, and try leaning the carb out, especially on the primary side, to see if that cleans up the launch. If it still bogs, then the carb is just too big for your combination, which is why the Q-jet worked so well. If you're into the Holley stuff, borrow a vacuum-secondary carb that you know works well and see if that improves the 60-foot times.
We'd suggest not attempting to run the nitrous until you get the normally aspirated combination completely dialed in. This means doing at minimum a jetting and timing exercise of making one change at a time and evaluating performance based on trap speed only. Do not use e.t. as the gauge, because if you make more power, it might spin the tires and slow the car down from an e.t. standpoint, but the trap speed will always increase. If you do this exercise you will have a good baseline from which to judge how well the nitrous performs. Nitrous is not supposed to be a crutch for poor tuning. Plus, those bad tuning techniques will only get you into more trouble with nitrous. Ask us how we know.
Riding on Air
Dave Hyatt, via CarCraft.com: I am working on a '70 442 convertible and need to choose which direction to go on the suspension. I want to play a bit in the winding roads and would like to get rid of the wallow associated with its size and 455-loaded nose. The car won't see more than a couple of thousand miles of service a year, but I'd like it to be comfortable enough to jump in and tally a few hundred miles at a sitting without rattling every bone in my ever-aging body. It seems everybody is pushing the poly bushings to firm things up, but my painter thinks it will be too harsh for the occasional Sunday cruise. I would like to bring the stance down a hair and I know that will help. I've been hearing about Air Ride's setup. How would it compare in performance and cost? Would it need a compressor and onboard tank taking up space in the trunk? Should I tubular this up front and out back? Right now, the car is sporting '70s technology and needs some love. I'd like to do it now while the body is off rather than dig it out after the body goes back on.