Join Date: May 2009
Location: Texas Hill Country
Screw CRT. Here's something you can try since you like road testing.
From David Vizard's Smallblock Chevy book:
"At this point I'll assume you have an HEI with a selection of advance springs and adjustable vacuum. The first step is to install the strongest springs at both locations on the distributor's advance mechanism. If your vehicle is a manual transmission, all of your tests can be done on a lonely stretch of road with a stopwatch. The technique involves choosing a suitably low starting rpm and timing the vehicle between two speeds. Let's assume that the motor has the potential to pull from 1,500 rpm. With the strongest springs installed, take off and have the clutch fully engaged in second or third gear at an rpm lower than the test's starting point. For example, we're working here with 1,200 rpm. Floor the throttle and time how long it takes to reach 2,500 rpm (my insert: floor it at 1,200 rpm and time it from 1,500 to 2,500 rpm). Progressively lighten up the primary spring until the best 1,500 to 2,500 rpm results." DV
Me again. I'm going to paraphrase this part because it's buried in a lengthy section on timing automatics. From here, you'd run either stopwatch trials from 2,500 rpm to redline or you could go for top speed. Increase the initial advance no more than two degrees at a time until your time or mph falls off or you hear detonation. If you hear detonation at a lower rpm, you may want to add the next heavier spring on one side of the advance mechanism and keep going with your high-speed testing. If you find out that you started your initial spring test with too much timing to begin with, you may have to pull several degrees out and start over. It's a little bit of back and forth but you can narrow it down nearly as good as being on the dyno.
Clear as mud?
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