Quote:
Originally Posted by Doug
Avman,
I assume your tires are about 25.6 or 25.8 inches in diameter and you made a typo when you said the rear axle ratio was 3.80 when it is actually a 3.08 ratio. (A 3.80 ratio seems strange for a GTO).
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The Toyo Proxes TQ drag radials are 275/40/17s and 25.8" inflated diameter. Tread width is about 10-11".
The ring and pinion gearset in the Quick Performance Ford 9" based rear axle assembly is, in fact, a
3.80 ratio. I chose that not being certain if my wife would want a 5 speed, thinking that it would be marginal but ok on the highway with a 1:1 final gear in the Muncie. I'll tell ya though, driving about an hour each way to and from the drag strip was bad, in that while I'm not sure how fast the 421 was spinning, it was close to 3,500 but sure sounded faster than my 440 did with my old 3.54 and 4 speed that turned 3,500 at 70 mph. Anyway, we have a TKO600 in the box in the garage and the 0.63 5th gear will have the 3.80 in 5th making the 421 purr like a tiger again. Also I posted the question "What are your 60ft times for those running 12.5 to 13.5 second quarter mile times?" and the range was 2.2 down to 1.7
I believe there's lots of potential for improvement in the timing and tweaking the Pertronix distributor to the best parameters for the advance curve. Also once I find the range where I can get the RPMs up at the launch and slip the clutch for maximum forward velocity without excessive tire spin THAT is going to definitely be worth a few 10ths.
I bought a hydraulic throwout bearing for my Roadrunner, and I'm getting the HitMaster launch control system tomorrow. I'm going to suggest that my wife let me get a hydraulic throwout bearing for her car now, since we're going to be working with the new transmission, and if the HitMaster works as well as I expect it to, and I expect a lot, we can add a HitMaster to her car, and by then I'll know how to adjust it, and I can set it up on her car. That way I can tell her the couple of hundred RPM range she needs to launch at, say 2600 to 2800 RPMs and all she has to do to launch is dump the clutch and mash the gas.
Thank you very much for the reply!
Edit: We are also about to install a replacement rear axle housing because QP put the wrong LCA lift bar brackets on the rear axle housing that's in the GTO now. The brackets with the "QP" in the picture have multiple holes for that end of the UMI lift bar to go in, making adjusting instant center easier. The new housing is set up strictly for coilovers as well.