Sometimes we run across a project so cool that it's worth waiting even years to see it completed. In this case it's a '68 Camaro convertible that was commissioned as a Pro Touring g-Machine more than five years ago. And since building a car like this takes lots of time and coordination, especially when you're dealing with so many different sources from all over the country, sometimes the project can seem to drag along. But the Camaro is not the star this month. That'll come in a later issue. Instead, this month, it'll be flexing its muscles for the first time.
To get back to the car for just one second, it's being built as a dual-purpose vehicle built to carve the tightest canyon corners and cruise with the top down. When deciding what to build next, the car's owner, who asked not to be mentioned until the car is completed, already has an 11-second street-strip car, so he definitely didn't need another one of those. No, this time he's building a true all-in-one machine. Fitted with a transplanted '84 Corvette chassis- both front and rear-and some wide-by-huge rolling stock with powerful Baer binders to slow it down, the drop-top F-Body would need some serious motivation to live up to its pre-fabricated reputation. Brothers Jim and Jeff Lirones, themselves NHRA Super Gas racers and canyon carvers who've set up shop in Tujunga, California, were called on to build a stout and reliable 406-cid small-block for this machine.
Rock SolidTo be able to assure the car's owner that his engine will never let him down, the Lirones brothers chose to build a completely new engine, instead of simply rebuilding a worn out old stocker. To that effect they started with an iron GMPP Bow-Tie block and bored the cylinders out to 4.155 inch. In went a 3.75-inch-stroke 4340-forged Cola crankshaft swinging 10.4:1 JE pistons on 5.7-inch Oliver steel rods. To give the Camaro road-course worthiness, Lirones also added a Canton road-racing pan and Melling high-volume oil system.
Up top the engine's owner was sure he wanted fuel injection but had no idea how much torque or horsepower would be needed to keep him carving the canyons with the best of them. So Lirones built what amounted to two different engines: one for max torque (490-plus lb-ft at 3,000 rpm) in case the car ended up a little on the heavy side and one for maximum power (475 hp at 5,600 rpm). Then, they thoroughly tested each combination on Westech's dyno before making the final decision on which engine to run in the car. It turns out that the car will be reasonably light, so the higher horsepower package won.
Since both motor combinations were going to be fuel injected, the selection of parts under the manifold was fairly straightforward. An off-the-shelf COMP Cams solid roller camshaft (PN CS-280HER-2/288HER-4) with a streetable 236/243 duration (at 0.050) and 0.552 lift and 112-degree lobe separation was used for both systems. For the torque series of dyno tests, Lirones installed an Arizona Speed & Marine TPI-style EFI system consisting of a modified long-runner intake manifold and a two-barrel throttle body.
To ensure an adequate air supply for engine, Lirones also installed a set of Air Flow Research 210cc CNC cylinder heads that they knew would help make this stroker a torque monster. This combo made big-block-style torque numbers even down where some big-blocks can't compete. How's 492 lb-ft of torque at only 3,000 rpm grab you? True, this combination peaked out fairly early with only 416 total hp at 5,000 rpm, but that much low-end torque would be enough to yank a locomotive off its tracks! And talk about towing power...if you've got a truck or very heavy street car, (4,000-plus lbs), this package would make it very fun to drive indeed.
More PowerWith the high torque testing out of the way, Lirones wanted to give the engine an extra boost in power but didn't want to sacrifice too much of its peak torque. They were, however, willing to move the torque peak up in the powerband, in order to make more top-end horsepower. Lirones swapped on Arizona Speed & Marine's modified Dart single-plane intake manifold with larger 36-lb-hr injectors and a 1,000-cfm four-bbl-type throttle body. Since the TPI system was controlled by the still effective, yet older ACCEL Gen VI ECU, Westech suggested that the new EFI system might be a bit more tunable using a new F.A.S.T. ECU.
With the new manifold, injectors, and throttle body bolted on and the F.A.S.T. ECU plugged in this new package was worth a huge gain in top-end power. And all that peak torque that really brought the 406 to life was not sacrificed that much. After all testing was completed, it wasn't hard for the engine's owner to choose the more powerful F.A.S.T. ECU/single-four barrel EFI system because he likes power. But we wanted to show you both systems' test results because it turned out that the TPI setup would make a killer everyday street motor.
The first trip to Westech's dyno saw the 406 equipped for max torque with an Arizona Speed & Marine-modified TPI-style intake and two-bbl throttle body. This combination made almost 500 lb-ft of torque at 3,000 rpm!
|With modified Dart single-plane |
intake manifold, 1,000-cfm four-bbl
throttle body, F.A.S.T. ECU,
and 36 lb-hr injectors
|MAX TQ:||487 @ 4,700|
|MAX HP:||475 @ 5,600|
|The graph below represents |
both engine combinations tested.
The one listed as “F.A.S.T. HP
and F.A.S.T. TQ” are the high-
horsepower packages, while the
“ACCEL HP and ACCEL TQ”
are the high-torque combination.