Project Chevelle: Performance Testing Tech Article
First things first, this is a project car. That means the engine, drivetrain, and suspension are going to be changed, probably more than once. It's all in the name of learning about our products and what they do in the real world. So in order to honestly evaluate the changes that we'll be making, we need to know what we're starting with.
In the videos and articles that we are creating to document our story with the old Chevelle, it's hard to convey exactly how the car feels. We can tell you it's slow, but it's better to have a number to back that up. We can tell you that it goes around corners like it's riding on mashed potatoes, but we need numbers. Power figures and lap times will prove that the changes we're making are actually improving the car. So in the interest of science, here are what may be the worst performance numbers you'll see outside of a Geo Metro...
The chassis dyno actually revealed more power than we thought we had. The first pull yielded 127 horsepower at a blazing 3760 RPM. Torque was at its peak of 228 foot pounds right out of the gate at 2100 RPM. It's at this point in a normal dyno session that you would start fine tuning to squeeze out as much power as you could get. Since this engine is not going to live in the car for much longer, we didn't want to pay for all that dyno time. Instead, we went straight to the goofiest thing we could think of; flipping the air cleaner lid. Not surprisingly, allowing the engine to draw air from the full air cleaner element instead of sipping through the little snorkel and goofy exhaust heat flapper door added a little power. We ended up at 130 horsepower and 233 foot pounds, our best for the day.
130 horses are not going to win any drag races, but it's not far from the net factory rating at the crank for a '72 307. Not bad for a 100,000 mile engine. It was also fun to see the 3 horse/ 5 foot-pound increase gained by flipping the air-cleaner lid. Turns out your buddy in high school who insisted that you flip the lid before you hit main street on Friday night was right all along.
Drum brakes have a bad rap. They are essentially 1900's technology that have somehow survived in the automotive world ever since. Under normal driving conditions they're okay, but when pushed they reveal some shortcomings. In particular, they get hot and fade after a couple hard stops. We wanted to see just how bad the brakes on our Chevelle would be at bringing the car down from 60 miles per hour, so we found a remote stretch of road and let 'er rip.
The first hard application of the brakes from 60 revealed that the car has a terrifying habit of immediately locking up the rear tires. You then have to lift off the brake to keep the rear of the car from swapping places with the front. The drums can't be blamed for this little bugaboo, this is a front to rear bias issue that we will address with an adjustable proportioning valve.
As you might imagine, all of this does not make for an impressive stopping distance. In our first attempt it took 208 ft. to haul the car down from 60. This distance increased dramatically from the first stop to the second; it took 235 ft. on the second blast when the brakes were hot. Blame the drums for that one.
There are several factors conspiring to keep the old Chevelle from changing course very quickly. The puny tires, soft springs, high center of gravity, and archaic suspension technology do not a canyon carver make. In order to find out just how bad it was, we set up a little autocross course in our parking lot. The results were comical.
One of the major problems with '60's and '70's suspensions lies in the frontend geometry. As the car leans over in a hard turn and the suspension compresses, it actually loses camber. That means the tire is being pushed out at the top and is no longer flat on its tread, but rolled over on the sidewall. Modern suspensions tend to gain camber as the suspension is compressed by pulling the top of the tire in. This change greatly increases lateral grip, especially with modern tires and wider tread.
On the best pass of the day, it took 18.2 seconds to get around the course. A well prepared track car would be in the 13-14 second range. This may not sound like much, but on a tiny course like this 4-5 seconds is an eternity. Not to mention the lack of predictability and overall colossal amount of work it takes to herd the Chevelle around the cones. We really have to do something about that steering ratio.
It's not really fair to poke fun at the old Chevelle. For its day it was just fine for driving to work or the grocery store, and that's really all this car was meant to do. We've all gotten used to seeing 500 horsepower SS versions of these cars that were built to go fast, and it's not fair to expect our base model to keep up. But we're hot rodders, and we believe that we can make anything look cooler and go faster. That's just what we intend to do with this car, and now we know exactly what we're starting with. Stick around, this is going to be fun!