April 2010 Performance Q&A

Tom Truty Jan 27, 2010 0 Comment(s)

Cool Trick
Have you ever tried something and you just couldn't believe it worked? I've been drag racing for way too many years, and this one really opened my eyes. As you all know, we've been trying to race Stock Eliminator for a couple of years now. Making enough power to push our '80 Malibu wagon into the 12s with a very restricted 305 is tougher than it seems. When we started this project, I never thought that making enough power was going to be the issue. Making the chassis work correctly or getting the rolling resistance down to make the car quick was what I thought was going to be the tough part.

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Back in 2007, we rolled out for our first race in Stock at the Winternationals. We ran 0.25 under our index, and I was very happy with that for our first time out. Well, after several engine rebuilds (and I'm being kind), we hadn't seen much improvement. What we had seen was that when the weather turns bad (high temps and density altitude) the car really slows down. Most of our testing has been at Auto Club Speedway in Fontana, California. The natural altitude is around 1,200 feet and the barometric pressure is very low for our altitude. My son, Daniel, and I felt that if we could run the index here at Fontana, we'd be fine to go up and run the Divisional race in Bakersfield, California. I looked back through my log books from Bakersfield for the past five years and found that the air hadn't gotten anywhere near as bad as we've been seeing at Fontana. As climate change would have it, the density altitude at Bakersfield this year was in the 4,200-foot range with the temps tickling around 102 degrees.

The wagon was right on the index for the first two timed runs, giving nothing to dial with. I'd tried everything, including draining out a quart of engine oil and taking out the last 8 pounds of weight, putting us dangerously close to minimum weight. This is when my good friend and fellow racer Jody Lang stepped in and asked what temperature we were running the car. I told him we were pulling out of the head of the lanes at 130 degrees F. He said "What do you think this is, a bracket race? Cool that thing off." I thought 130 was cool. We'd normally run our bracket package in the 150 range, pulling out. For the final run we cooled the engine down to 100 degrees (tough when it's 102 outside) and sprayed down the intake manifold with ice water. Daniel pulled out for his final timed run and the car picked up 0.20 second from the prior two runs! I was very surprised that the temp change made that much of a difference. I was very skeptical with the gain for first round and dialed him up a little to be safe. With the same cool-down procedure we were rewarded with a 0.23 under 12.92 e.t.

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Well, contrary to how the saying goes, you can teach an old dog new tricks. Thanks to Lang we were able to make it into the field. I would have never believed it if I hadn't done it myself.

Diaphragm Dilemma
Q: I am a subscriber and am trying to rebuild the Holley carb off my '60 Corvette. I doubt any work has ever been done on the carb; I have owned it since 1984 and have not worked on it before. I've been following the steps as described in your article on how to rebuild a Holley carb, but I decided to also rebuild the vacuum diaphragm. Do you have a recommendation on where to find info on rebuilding the vacuum diaphragm? There is a little ball bearing that came out after I disassembled it, and I don't know for sure if I'm putting it back where it belongs. Also, the diaphragm holes do not seem to align properly, regardless of which way I turn it to reinstall it. Thanks for the help.

Tom Richards
Flower Mound, TX

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