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Tech Question
Travis Vela, Stafford, TX, 1974 Plymouth Roadrunner 318
Hey Rick, how's it hangin'? I know I don't have the most popular and lightest B-body in the world, but I'm having trouble finding curb weight info on my 74 Roadrunner. Also I'm wondering if there's any effective ways to put her on a major diet, as I hear they're pretty damn heavy! I plan to make a handler out of it. But all I can do is search for stuff that they actually MAKE for my car, like the light Wilwood brakes, tube control arms or with a little more saving, a tubular k-member, lighter bucket seats (I still have a bench), aluminum heads, Sanden A/C compressor, etc. Will fiberglass make a difference (all I can find is a hood)? But what really makes my late B-body heavy? Thanks a bunch, Rick. I always look forward to your wisdom.
Travis-
First, a correction: Your car is a Plymouth Road Runner. Not a Roadrunner.
The crux of the problem is the rubber-isolated front suspension and K-member. In a pre-'73 B-body, the K-member tied together the front longitudinals, making for a rigid, lightweight structure. When the design became isolated (for NVH), each front rail became a floating (cantilevered, actually) "prong" that needed to be amply stiff independent of any other part of the car. To accomplish this, lots of mass was added. The bumper system, to meet Federal regulations being phased in, also added a LOT of weight.
Even more unfortunately, most of the added weight was on the nose, trashing the early car's near-neutral balance.
The chassis can easily be stiffened to the point where it is actually better than '62-'72 B-bodies, by the installation of aluminum blocks in place of the rubber isolators (www.firmfeel.com). The improvement is startling. But weight reduction is another matter, and, in practical terms, impossible. You can take weight out, of course, (aluminum heads, fiberglass, etc.) but you will always be at a disadvantage vs. the earlier cars. That, however, doesn't mean you shouldn't do it -- quite the contrary! You could, once the K is no longer floating on rubber, Swiss cheese it like mad with a good hole saw (and lots of time). You could do the same to the bumper reinforcement and brackets, dump the guards, etc. Every pound helps!
Tubular K-members, as a rule, are not recommended for street use. Most Wilwood calipers are also not really streetable, having no environmental seals ("boots") on the pistons.
Wild guess: Your car is 3800-3900 pounds. Why not scale it though?
Rick
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