In the grand scheme of small-block Chevy performance engines, there's a ton of information on the first-gen engines, and every month there seems to be more on the new Gen III and now Gen IV small-blocks, but the LT1 engine-the Gen II if you will-seems to have been overlooked.
Our pal Tim Moore got the call to build a solid-performing LT1 small-block that would occupy the engine compartment of a certain Impala SS owned by Joe Freeman. Since the Impala SS is a hefty sedan, torque is the name of the game if you want good street performance, so this demanded an infusion of cubes.
Moore's first step was to contact Scat for one of its performance cast cranks along with a set of 4340 forged-steel I-beam rods to add stroke to the 4.030-inch bore. He filled the cylinders with forged flat-top SRP pistons and a 11/416-inch ring package. The stroker package required some careful block clearancing near the oil-pan rail to clear the rods. The minimum clearance here is 0.050 inch, but even more is advisable. The problem is you must remain conservative in order to avoid hitting the factory water jacket located nearby, so don't get carried away with the die grinder. This combo also required internal balancing because we were running the stock front damper, which doubles as the front accessory drive pulley.
Moore had already decided to invest in a set of Airflow Research 180cc aluminum heads, figuring that the smaller ports would create enough airflow to help build torque, since the LT1 intake offers extremely short intake runners that tend to hurt low-speed torque. These smaller AFR LT1 180cc heads produce more airflow than many larger competitors, which will tend to improve the midrange torque. As you can see from the power curve, the torque curve is amazingly flat, which just makes the Impala SS that much more fun to drive.
With a solid 11:1 compression ratio dialed in with the AFR 64cc chamber size and flat-top pistons, Moore knew he would have to add some camshaft duration to the mix to avoid detonation problems on California's marginal 91-octane pump gas. Looking through the Crane catalog, Moore ran across a single-pattern hydraulic roller with excellent cam lift-218 degrees at 0.050 inch-combined with 0.498-inch valve lift. The best part is that Crane went to the effort to establish an Executive Order that makes this cam 50-state legal with the smog police, which in California is a must-have option for a '90s daily driver. Moore spec'd the rest of the valvetrain all from the Crane catalog, including 1.5:1 narrow-body roller rockers to clear the stock LT1 valve covers, springs, retainers, keepers, and pushrods to create a durable valvetrain.
While an LT4 intake would probably have improved peak horsepower, Moore chose to have the stock intake port-matched to the new AFR heads. Slover's Porting in North Hollywood, California, did the work and also trimmed the step formed just behind the larger 58mm Holley LT1 throttle-body. Without the mild porting, there is probably little to gain from using the larger throttle-body. Because this stroker would easily exceed the stock fuel injectors' capacity, Moore also stepped up to a set of 30-lb/hr ACCEL fuel injectors, which even at the stock fuel pressure are capable of supplying sufficient fuel to make almost 500 hp.
There's also little reason to invest in a good set of heads and a more aggressive cam if you don't give the engine every opportunity to breathe. This meant bolting on a set of Borla stainless steel headers matched up with stock converters and a stainless Borla 211/42-inch exhaust system complete with an H-pipe.