We've been spending money and turning wrenches on our Street Sweeper Chevelle project since we first got it in the April 2007 issue of PHR. Quite frankly, we were tired of futzing around and it was time to burn some rubber. We could've gotten totally anal about it, building a rollbar, relocating the battery, wiring in a rev limiter, and installing a roll control, but we were starting to think our '68 Malibu was turning into a science project instead of a bona fide street/strip car.
It was time to take stock of our work and find out what worked on our Chevelle, and what didn't. Message forum opinions, engine dyno results, and past experience can only take you so far-at some point, you need a signpost to point the new direction. As fate would have it, the Fun Ford Weekend was coming to town for their season ender at Fontana's California Speedway. Unlike Fun Ford's typical all-Ford show, the finale (which was held on October 20) would allow other domestic makes, including our Chevy.
Pro Touring or Street Strip?...
Pro Touring or Street Strip? Take your pick-the Street Sweeper Chevelle is both. Here I'm goofing around mid tire change at Fontana just after changing the passenger-side Nittos over to Mickey Thompsons. Pro Touring haters can step to the left, Pro Touring lovers move over to the right. Check out Steven Rupp's Fairlane just to the left.
True Street-The Ultimate Test
I was particularly interested in True Street, because it's designed for licensed, insured, and registered street cars. Even better is the 30-mile pre-race qualifying cruise, which all True Street racers must successfully complete. When True Street was first started in 1993, the idea was to move "street car racing" back to true street cars, hence the name. Run 'em in hard traffic conditions long enough to weed out the race cars, then run 'em three times back-to-back down the track with DOT tires while the engines are still heat soaked. And the real kicker: From the beginning of the cruise until the last lap, nobody's allowed to pop the hood.
This kind of mechanical abuse is enough to scare away most guys, myself included. In the 14 years since I helped create the class, I had yet to run in it. That was about to change: The Street Sweeper was ready to pound asphalt! The plan: run the test and tune the day before True Street, and flush out any lastminute problems. Our first problem actually turned out to be a blessing in disguise: True Street requires DOT-legal tires for the cruise and drag runs. We already had our 28x10.5 Mickey Thompson eT drag slicks mounted on Summit Star rims, and they weren't legal. Bummer. But we did have a backup set of 26x10 Mickey Thompson eT streets mounted on Centerline Telstars. They were from a previous project car, but other than looking ridiculously short, they fit the Chevelle fine.
When it's time to fill out...
When it's time to fill out your tech card, take the time to fill it out completely and legibly. It won't change the results of your racing, but you'll be really pissed off if your name gets mispronounced over the PA system, or if a magazine prints your name wrong, or leaves out your information entirely.
After some debate, we decided to do the Friday test and tune on the bigger 28x10.5s, then do True Street on the smaller 26x10 DOTs. At least we'd have a set of data with both tire sizes, and that turned out to be a very useful piece of info for later on.
The day of the test and tune arrived, and we were filled with excitement and trepidation. We loaded up the Street Sweeper with the slicks and skinnies, boxes of tools, camera gear, spare parts, lounge chairs, and a giant cooler full of drinks and vittles. The great thing about A-bodies is that they can swallow virtually anything. Built at a time when trucks were still for farmers, the midsize five-seat Chevelle was the SUV of its day.
With a full load of 91-octane, we headed to Fontana. At the drags, we picked out a good spot and unloaded our junk. We swapped on the 28x10.5-inch slicks and skinnies, then went to tech inspection. If you've never been through NHRA tech with your street car, here's the low down: You want to be prepared. There's nothing worse than getting this far and being turned away for something stupid. In theory, you're supposed to buy an NHRA rule book and study it (which we recommend), but the cliff notes version is that you need a newer Snell-rated race helmet (not a motorcycle helmet-it's not treated with fire retardant), an overflow catch can for your radiator, working seatbelts, redundant throttle return springs, and a driveshaft safety loop if you're running slicks. These are only the basics. Cars going faster than 11.50 also need a rollbar, five-point safety harness, and stick-shift cars need a blow-proof bellhousing. We would be happy to break into the 11s on this first set of runs, so we weren't worried about the rollbar...yet. At tech, we got a clean bill of health and breathed a sigh of relief.
The first time you take a...
The first time you take a new project car to track tech inspection is always a little nerve racking. Here, the tech official is looking for the Snell rating located inside the lining of this Bell helmet. When buying a helmet you'll want the current standard, which is SA2005.
Our next stop was the digital scale. With driver, an empty trunk, and a full load of fuel, the Street Sweeper weighed 3,666 lbs. That's about average for an all-steel '68-72 Chevelle with no A/C or heater. With our 496-inch big-block Chevy motor twisting the dyno to 626 hp and 635 lb-ft of torque, we knew it was reasonable to expect 11-second e.t.'s right out of the box, and we were right. All three of the runs we made on Friday's test and tune clustered tightly in the 11.80 area, and ranged from 11.75 to 11.86. We were pleased that on the first outing, everything operated as expected: Our previous oil-starvation issues were completely gone, and our concern over potential tire rubbing with the 28x10.5-inch slicks was a non-issue. In short, this was a shakedown test designed to find serious problems- not the time to set the world on fire. We were satisfied that the Chevelle would run good the following day without breakage, but how would the shorter and narrower DOT tire fare?
We bolted the NTO1 Nittos back on, loaded up the Chevelle, and made the hour-long drive home with a smile plastered on our faces. even the heavy Friday evening rushhour traffic didn't bother us-or the car, which showed a cool 160 degrees on the new Stewart-Warner temp gauge. Saturday morning, we pulled the Nittos off, and bolted the 26x10 eT Streets on. We figured it would look better if we just showed up with them already on; plus it would make things easier once we got there. (Side benefit: We enjoyed the looks we got with barely street-legal "grooved" slicks.)
If you've done everything...
If you've done everything right leading up to race day, you can sit back and relax when you're at the track. Here's our engine builder, Andy Mitchell of Outlaw Racing engines (Upland, CA), taking a break on the day of the True Street competition.
In the pits, we met our engine builder, Andy Mitchell, where he suggested we lash the valves one more time. With over 2,000 hard street miles and three drag runs on our 496, he thought it wouldn't hurt. Yeah, hydraulic rollers don't normally need adjustment, but our valvetrain had a touch of clatter that we easily cleared up. This bagged us some extra duration in the deal, too. After one last hard look in the engine room, we closed it up and fastened the hood pins. This was the last time we'd see those COMP valve covers until after it was all over. All the preparations were done, so we set up the grill under the easy-up, fired up some cigars, and watched the crowd gather as we barbecued our burgers and cheese brats. As showtime crept near, we were joined by the rest of our friends. We reasoned that we might not have the fastest car, but we sure as heck had the best party.
By the time we got called to the staging lanes for our 30-mile street cruise, the mercury was topping 90 degrees. Some of the other True Street competitors were visibly nervous, but with all the hard street miles under our belt, we just relaxed and enjoyed everything. Due to a snafu with the event staff, our 30-mile drive took just over an hour, with the Street Sweeper Chevelle idling in traffic far longer than anticipated. Nevertheless, our Jeg's radiator and mechanical fan kept things cool, and the 496 rumbled on without protest.
Once the pace vehicle brought us back to the track, we had a few minutes to grab a bottle of cold water and set the tire pressure at 15 psi. We wouldn't have the chance to change the pressure after the first or second run, so we went conservative. A Chevelle with a torquey big-block is going to load the little tire pretty hard, so we felt it was better to slightly over inflate rather than under inflate, on a smaller-than-optimal tire. We also set the right rear Air lift bag to 15 psi, and let all the air out of the left-side airbag. This would pre-load the right side at launch, leveling out the car for a straight leave. (See photo at the top of page 64.)
The purpose for us running...
The purpose for us running the True Street Challenge (a 30-mile cruise followed by three back-to-back quarter-mile dragstrip passes) was to find out if our 496ci big-block was up to the task. Nicknamed "The Howitzer," our 4.25-inch stroke BBC packs a dyno-verified 626 hp at 5,900 rpm and 635 lb-ft of torque at 3,800 rpm.
We made our three back-to-back runs without incident, all of them produced with identical technique: Wet the tires, pull forward for an ample burnout ending in second gear, stage shallow, flash the converter to 3,000, and shift at 5,900 rpm (our engine dyno power peak). When the dust settled, we averaged 11.764 for our three runs, which was good enough to place sixth overall.
The goal of our '68 Chevelle project car has always been to run 11s on pump gas without the aid of a power adder. Strictly speaking, we achieved that goal with room to spare on the first time out, and we did it in one of the harshest environments imaginable-True Street competition. Nevertheless, with a dynoverified 626 hp, there's more un-tapped potential in the Chevelle. Given the dyno numbers, we'd like to better the strip performance without going too crazy.
For one thing, we're a little miffed by the low trap speed, which by all accounts should be in the 117-120-mph range for a motor of this output. One thing we'll be looking at is fuel starvation (we're currently running a 9/32-inch-diameter stock fuel line from the original 307 small-block). A larger fuel line and a trip to the chassis dyno for some tuning should reveal what's going on here. Also, we feel the converter may be a tad on the loose side. Although we spec'd a 3,500-rpm stall speed from TCI (a Super StreetFighter 10-inch), we're consistently seeing over 5,000 flash rpm at launch when we hit the gas.
As far as the results from different size tires go, it was interesting to see that the shorter, narrower tire ran the quickest- even though the engine was absolutely heat soaked and the ambient temperature was screaming high. On one hand, it's a testament to the streetability of edelbrock's Performer RPM Air-Gap intake, but it also tells us we're crossing the finish line closer to our peak power rpm with a shorter tire-i.e., we're too tall on the gear ratio, or we're too loose on the converter for our power.
Whatever the case, we will not be putting an intrusive rollbar on the Street Sweeper Chevelle, nor will we be turning it into a race car. This is a fun street car, and we are firm on this. We may get kicked out of the track once or twice before putting a halt to our mods, but we can get around some of our drag testing limitations by running eighth-mile for a while. We know we can go quicker and faster, so stay tuned. Next month, we'll be looking into some fuel system fixes, including a largerdiameter fuel line.
We easily broke into the 11s...
We easily broke into the 11s on our very first run, with an 11.86 at 113 mph. We ran the brand new 28x10.5-inch Mickey Thompson slicks on Friday test and tune (shown), but we were restricted to using the shorter, narrower 26x10-inch eT Streets on Saturday, due to the DOT tire rule in effect for True Street.
We've been updating readers...
We've been updating readers on the Chevelles.com message board regularly, and right after we made this first track outing, we posted the dragstrip numbers from this story. The overwhelming consensus was that with only 113-mph trap speed, our 626hp big-block was underperforming. During the intense questionand- answer session that followed, some readers suggested our 3/8-inch fuel line was too small for our fuel demand.
We're just teasing you with...
We're just teasing you with tidbits from next month's installment, but here we are on Westech's SuperFlow chassis dyno after increasing the fuel line diameter and installing a new OPG fuel tank with a Moroso sump kit.
There's nothing better than...
There's nothing better than having a fist full of 11-second timeslips to stuff in the glovebox of your street Chevelle.