Saturday, April 15, 2017

The Story of an Old Firebird, Part 5....

This section will cover the body/chassis, and the “weight loss program” I put the car on.

The car as delivered handled extremely well. With the 1.25” front sway bar and the .875” rear sway bar, high-rate springs, and Pliacell shock absorbers, it cornered flat. I added Koni adjustable shock absorbers, and set them about half way between very little damping, and break your teeth. The special variable-ration power steering that came with the Y99 handling package, and the small diameter fat-rimmed “Formula” steering wheel made the car steer like a Go Kart. During the course of construction, I cut a full coil from the front springs, and made some lowering blocks for the rear leaf springs. Cutting coils off a spring not only lowers the car, but also raises the effective spring rate. The “best” way to do it is to get shorter springs made, or find some others in the parts book that do what you want, but cutting a coil off is a pretty cheap, effective way to drop the car.

The rear lowering blocks were 3/4” think aluminum blocks I had made at Tubby Gallup’s (I’m pretty sure that’s his name...it’s been almost 40 years!) place, and he also fabbed some longer U-Bolts for me. Adding lowering blocks pushes the rear axle up into the chassis, dropping the body down lower over the axle.

I also ordered some solid body mounts from Herb Adams’ “Very Special Equipment” catalog, along with some front subframe reinforcing struts. The solid body mounts eliminated any deflection caused by the big rubber “biscuit” type body mounts, and moved the front subframe about 3/4” closer to the unibody, effectively “channeling” the body down over the frame. The front struts he sold attached to the pinch-weld area of the firewall in two places, and then ran down to the forward stud for the upper control arm. You loosened the big nut used for front end alignment, remover some alignment shims, dropped the tab on the end of the strut in place, and tightened the nut back up. A trip to the alignment shop was required, as removing the wrong amount of shims had adverse effects on your front camber and caster!

With the cut front springs and the aluminum subframe mounts, the front dropped about 1-1/2 inches. Along with the 3/4” drop in the rear, the car had a pretty mean appearance. Today we’d say it had “Stance”, but back then we just said it was lowered, or had “a mean rake”.

The front and rear sway bar mounts were also changed from rubber to aluminum where the bars mounted to the frame, and the end links were replaced with new ones fabricated using spherical rod ends, or “Heim Joints”. This completely eliminated any deflection in the bar mounting, and made the bars act instantly, rather than having to take up any “squish” or slack in a rubber mount. I didn’t go “Full Race” on the suspension by replacing the front control arm bushings with solid ones, as I’d had before-and-after rides in cars that had that done to them, and it 100% completely ruined the car for street use. You can get away with that on a nice, smooth race track, but solid suspension bushings on the street are completely unlivable. These days we have polyurethane suspension bushings (I have them in my Supra), and while they’re stiffer than OEM bushings, they’re nothing like metal ones.

The only other change I did was to replace the OEM idler arm in the steering linkage with a heavy duty one made by Moog. The arm itself was much thicker, and the bracket where it attached to the frame was twice as thick as the OEM idler arm. It also had grease fittings on both pivots.

So that was it for the chassis. Pretty stock, really, with just a few carefully chosen aftermarket parts.




I already knew that the engine was going to be pretty stout, and without spending a significantly greater amount of money, it was going to make about as much power as I could reasonably expect, which led me to ponder what else could I do to make it faster?

A famous race car designer once said: “More power makes you faster on the straights; Less weight makes you faster everywhere”.

OK, I’ll make it lighter! But how?

There’s an old saying in the aircraft industry: “The best way to remove one hundred pounds is to find 1600 places and remove one ounce”.

I took both sayings to heart, and started looking for “1600 places to remove one ounce”!

Since this was going to be a one or two passenger vehicle, and was not going to be a daily driver, the back seat, seat belts, and mounting hardware could be pulled out. This saved 30 pounds, and got me thinking about how to get more weight out of the car.

Since I was going to relocate the battery out of the engine compartment for better weight distribution, I had to pull the carpet out to run the new cable. I had to pull the front seats (35 pounds each!) out of the car to get the carpet out, and I noticed all these asphalt-and-paper sound deadening pads absolutely everywhere. They were under the carpet, under the seats, under the dash, stuck to the firewall...just all over the place. After I pulled them all out and dumped them on the scale, I realized I’d just pulled another 25 pounds out of the car! This got me really going.

The F60-15 spare tire on the 15x7 steel rim, along with the jack, jack base, handle, and J-bolt and wingnut, weighed in at a staggering 75 pounds.

The new, lighter Corbeau GT bucket seats I was going to use weighed 40 pounds less then the seats the car came with.

All the reinforcing bars and struts, and the mounts and their hardware, for the “5MPH” front bumper weighed 50 pounds. I wouldn’t need them as I was already in the process of pulling a mold off the front Endura bumper so I could replicate it in fiberglass, so out they went.

The fiberglass front bumper replacement I eventually wound up with removed another 100 pounds from the car.

Removing the stock exhaust system, muffler, pipes, hangers, and hardware saved another 70 pounds.

The aluminum intake manifold was 15 pounds lighter than stock, and the aluminum brackets and smaller hardware I used for the rear bumper saved 5 pounds.

There were numerous other brackets that I fabricated out of aluminum, painted them black, and when they were on the car, nobody knew. These saved another 10 pounds.

Any place there was a non-critical fastener, bracket, strut, or other fiddly bit, I either eliminated it, made it out of aluminum, drilled holes in it, and/or used a smaller size bolt to hold it on. Nobody ever saw most of these “little things”, but I wound up with a car that was a real sleeper.

The lighter flywheel and clutch assembly was a wash because I replaced the aluminum bellhousing with a Lakewood scatter shield and block plate. I’d seen cars where the clutch let go, and it did quite a bit of damage, and I wasn’t going to let that happen. Plus, the weight was within the wheel base, and mounted down low, so I didn’t worry about it.

And what’s almost as important as removing the weight was where I removed it from. Most of the weight came off the nose of the car, as in the case of the battery. The 40 pound battery, which was located in front of the engine, and right at the top of the radiator, was moved to the floor of the car behind the passenger seat where the rear seat had been. This got that amount of weight within the wheelbase, and about 24” lower than it had been. A small thing, but “small things” like that can improve the handling of the car, making it easier to turn, and lowering the center of gravity, resulting in flatter cornering.

The total weight savings amounted to over 400 pounds, or more than 10% of the weight of the car.
I didn’t go full-on, bat guano crazy ripping things out, but I did get a significant amount of weight out of the car.

I still had windshield washers and wipers, a fully functional heater, carpeting, my center console, an AM/FM stereo radio, and the side impact beams in the doors of the car, one of the reasons the doors on a second generation F-Body weighed so much.

But it was quite a bit lighter than stock 73 Firebird, and it was worth it.

3 comments:

  1. If only you had replaced the air in the tires with helium. (kidding)

    Very thorough weight reduction program.


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    1. Thanks. I got it to the point where taking much more out of it would have started to have some serious impacts on it as a "street" car. I needed the heater (core, hoses, clamps, and coolant was about 35 pounds) because I took it out in the winter time when the roads were dry. Same with the windshield wipers; even though I didn't deliberately take it out in the rain, you never knew in Illinois when a storm would pop up.

      The side impact beams in the doors (50 pounds total, from what I'd read) could possibly save my life, and were a massive PITA to remove with the outer door skin in place.

      The replacement front fenders I used (Trans Am fenders with the air vents) were acid-dipped to lighten them a tad, and I also ran without the inner fender assemblies, which I forgot to include on the list. I had a steel Trans Am hood (also acid-dipped) and a shaker scoop/air cleaner to replace the ridiculously heave fiberglass Formula hood, but never got it mounted on the car. That would have saved another 30 pounds or so.

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  2. Yep, it's ALWAYS about weight... Those race cars look pretty on the outside, but are gutted inside!!! :-)

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