So far, life in the fat lane has been good to us. As we mentioned last month, we immersed ourselves in the world of rotund Caprices by finding, purchasing, and drag racing a rather clean '96 Caprice we picked up for $3,000. With a smattering of mods (Edelbrock cat-back, Level 10 tranny with 2,400-stall converter, Metco control arms, 3.73 gears, and Nitto drag radials), we managed to whittle our e.t. from a ho-hum 15.251 at 91.11 mph to a respectable 14.802 at 91.77 mph-not bad for our first few weeks of ownership!
Our round of mods this month focuses on adding some time-tested bolt-ons that we'll track-test and dyno-test thanks to the capable hands at Crazy Horse Racing in South Amboy, New Jersey. What better way to show how power at the wheels really affects dragstrip performance in the real world than to run back and forth from the track and the dyno? Strapping our Killer Whale onto Crazy Horse's Dynojet 248c revealed a baseline of 245.6 rear wheel horsepower at 5,350 rpm and 320.6 lb-ft of torque at a mere 2,900 rpm. Considering the car is rated at 260 hp and 330 lb-ft of torque from the factory, the Killer Whale is sure running strong with just the Edelbrock cat-back exhaust.
One of the most fabled no-cost upgrades to any GM car is to de-screen the factory mass air meter, that is, remove the meter's screen on the inlet side. Designed to straighten airflow into a more laminar fashion before it hits the meter's hot wire element for more accurate readings, the screen has proven to be a minor restriction on flow benches and dragstrips alike.
For us, this five-minute modification netted us an e.t. reduction of zilch (rounded off, that's a big zero). On the dyno, however, we did find some slight gains in the low- and middle-rpm ranges. For instance, at 4,000 rpm (the highest point of gain) we were up from 215.8 hp to 220.8. Torque also swelled by 6.4 lb-ft at 3,400 rpm, where it was up from 309.8 to 316.2 lb-ft. At the peak points, however, there were no gains, just equal numbers.
Being consistent with our first round of low-dollar upgrades, we then moved to the air filter and induction system. We replaced the convoluted and restrictive air intake system with a cold air kit we found on eBay. The kit simply replaces the forward air silencer and airbox with a straight steel tube and an open-element air filter.
Although the seller considers it a cold air system, in truth, it's not because it draws air from within the engine compartment, including its heat. But for the money ($43), we couldn't complain or resist being our cheap selves. The installation literally took all of 15 minutes to complete, as the factory parts came off with ease. A noticeable gain in underhood noise was rewarded with a drop in e.t. to 14.651 at 92.10 mph for a .151-second drop in e.t. and a 0.33-mph gain. The poor man's performance upgrade was certainly worth it, and to prove it, Crazy Horse's Dynojet measured a gain of 3.7 rear wheel horsepower and 9.5 lb-ft rear wheel torque, bumping our figures up all across the board with our peaks now at 249.3 rear wheel horsepower at 5,600 rpm and 330.1 lb-ft rear wheel torque at a stump-pulling 2,800 rpm.
Next up, we went with an underdrive crankshaft pulley. We knew it would net gains both on the track and the dyno, but the question was, by just how much? We were able to find a used unit for $78 from-you guessed it-eBay. The seller didn't know what brand it was, but he threw in the appropriate drivebelt and hardware. To no surprise, the modification helped horsepower at higher revs as our trap speed climbed to 92.55 and our e.t. went down to 14.520, despite the loss of favorable weather conditions. On the dyno, we found the unknown underdrive pulley to be worth 3.9 rear wheel horsepower, and the dyno graph clearly illustrated how most of the improvement came at 3,500 rpm and above. There was no gain at peak torque, so our rear wheel power tally was now at 253.2 horsepower and 330.1 torque.
Next up, we had to buck up and spend some coin on what we consider the first of the more substantial modifications. With the minor bolt-ons behind us, it was time to free up the intake tract with a larger throttle body. We elected to use Edelbrock's twin 52mm assembly (PN 3809) to replace the original 48mm double-barrel unit. Aside from offering greater airflow from larger-diameter bores, the Edelbrock piece also enhances total airflow by incorporating a smoother transition from the ovoid opening into the two individual throttle bores. Also, Edelbrock includes a new TPS (throttle position sensor) with its throttle body to save time and hassles. For those with more serious applications, Edelbrock also offers a larger 58mm unit, but this would be overkill for our project.
When installing a throttle body onto any twin-bore TPI or LT1/LT4 engine, keep in mind that engine coolant is designed to pass through it to prevent the throttle blades from icing during cold starts. When removing and installing the coolant manifold bolted to the underside, keep in mind that you'll be opening up the cooling system and a quart or so will leak out.
With the new Edelbrock throttle body installed, Chris Winter's Dynojet was able to measure a very sizable gain of 8.1 horsepower and 23.1 lb-ft at the wheels at peak output. But the real kicker was how much torque and power it picked up down low, which shows how a smoother air inlet transition at the throttle body can greatly help low-rpm performance. For instance, at just 3,300 rpm our engine was making 7.6 more rear wheel horsepower and 12.0 more lb-ft of torque. This was backed up with another run on the dyno, and conclusively, we were impressed. Now our tally was up to 261.3 rear wheel horsepower at 5,600 rpm and 353.2 rear wheel torque at 2,900 rpm.
At the track, we were able to drop our times to 14.405 at 92.81 mph for a reduction of just over a tenth (0.115 seconds) and a slight bump in trap speed of 0.26 mph. Our weather situation didn't help things on the track since the heat sent our thermometers north of 90 degrees Fahrenheit. This made our runs all the more impressive. Our dyno figures were all corrected to SAE standards, while our track times were left raw.
Making Headway-Sort of
With the engine freed up of some extra power through simple bolt-ons, our next move was replacing the exhaust headers. We've seen a few offerings on the market, but were never too satisfied with the quality or fit of the products. Rather than risk it with a header of questionable lineage, we elected to use Edelbrock's quality TES (tubular exhaust system) shorty-style headers for more power and, of course, less weight. They replace the factory cast-iron manifolds and meet 50 state emissions requirements since the catalytic converters are retained in the factory locations and the AIR (Air Intake Recirculation) system is left untouched. Available in a ceramic-coated or Ti-Tech finish for a bit less moolah, we chose to go with the latter to stay in line with our budget buildup.
With our Killer Whale on the lift at Crazy Horse Racing, proprietor Chris Winter once again helped install the parts. Removing the factory manifolds was an easy task, necessitating the removal of just a few pipe fittings for the EGR tube on the passenger side and the two aforementioned AIR injection pipes on the topside. It's easiest to remove everything underneath, so a vehicle lift is strongly recommended when performing this upgrade.
The driver-side header is a direct replacement. Because it bolts right onto the existing catalytic converter/downpipe assembly, installation took about 35 minutes. The passenger side, however, was another story altogether. Here, you need to modify the downpipe by cutting off the lead tube that goes to the front of the catalytic converter and weld the new Edelbrock tube into place. The purpose is to remove the tight radius of the factory downpipe that happens to be the most restrictive part of the exhaust system. Edelbrock also wants to gain additional clearance by the starter so it can fit longer primary tubes in the tighter confines of the passenger side.
Another time-consuming task here is the fitment of the gosh-awfully difficult-to-reach EGR feed tube that has a habit of refusing to line up. And when it finally is lined up, it'll take another leap year to get the one bolt that holds everything together into place and tightened. If it is this tough in a Caprice, we have a lot of sympathy for you F-body owners out there with an LT1. In total, the headers took us four hours to complete, but we were happy to find no leaks and excellent fit once everything was torqued down.
Back on the dyno, we were somewhat surprised to find no gain in power. Chris and I concluded that on a bone-stock LT1 the factory manifolds are still keeping up and are not a restriction at our power level. We didn't lose any output-the power curve overlapped our previous best within a few ponies, so we maintained our measurements of 261.3/353.2 at the wheels. Also, the headers were flowing into the restrictive stock catalytic converters, which negated any gains we might have had.
The good thing is, we are now ready for our future mods. The bad thing is, we've hit a wall as far as bolt-ons go, which in turn means that if we want more power, we'll have to either add a power adder of some sort or get into the motor. Truthfully, this is a perfectly fun car as it is, and we should stop here. But of course we're fools and will continue down the yellow brick road in our quest for more power and quicker timeslips.