Chevy LT1 Engine Build - Power Play

The Second-Gen LT1 Is A Great Engine--Our Plan Is To Make It Better!

Terry Cole Aug 1, 2000 0 Comment(s)
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Manley 6-inch forged H-beam connecting rods proved to be the perfect choice for our combination. Not only are they strong, but they are light as well. Nicely machined SRP pistons round out the reciprocating assembly. With a short-skirt design, they will help keep the weight to a minimum. Rounding out our bulletproof short-block are items like the Cloyes heavy-duty single-roller timing chain and gears, a complete valvetrain assembly from Crane Cams, performance gaskets from Fel-Pro, and top-of-the-line fasteners from ARP.

First consideration was the engine block itself. In order to maintain the LT1 heritage (and logistically install it in a fourth-generation Camaro), it was necessary to use a late-model case designed to accept the front-mounted distributor and accommodate the reverse cooling water flow and its accompanying direct-drive waterpump. But, since we were gunning for lots of torque, we had to strengthen the less-than-stout main bearing saddles. The first step was to contact the folks at Pro Gram Engineering for a set of their billet splayed four-bolt caps. These well-machined parts go a long way in beefing up the lower end. As for a crankshaft, there are plenty of cast-iron units out there. And, since we were determined to add a significant number of cubes, we knew we'd have to contact one of the industry's custom crank makers to find a strong forged arm. Here, we turned to Cola Crankshaft Company. They provided a 4-inch stroke, non-twist 4340 forging that is, to say the least, a work of art. Not only does it accept the smaller-diameter flywheel and one-piece rear seal that identify a late-model version, but it is also drilled to allow use of a bolt for holding the harmonic balancer in place.

As for the rest of the reciprocating assembly, a lot of thought went into what connecting rods were needed and what pistons to use. On both fronts, we didn't skimp, opting for a set of Manley forged H-beam units and SRP forged slugs. And since we were planning on adding a good dose of compression from the supercharger, we had the pistons created so that the final compression ratio was in the neighborhood of 9.4:1, a full one point less than the factory hypereutectic versions.

With the short-block laid out as tough as possible, attention was given to the engine's breathing capacity. The biggest decision was in what heads to use. With an industry ripe with stellar designs, it wasn't an easy choice. But when all the information was assessed, we chose to go with Air Flow Research's LT1 design, which is a direct replacement for the factory units. That's where the similarity ends, though, as these CNC'd beauties feature 2.08-inch intake valves and 1.60-inch exhausts. And, once Beck was finished massaging them, they showed an impressive 280-cfm intake (at .500-.600-inch of valve lift) on the flow bench! Impressive, to say the least.

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Topping off our potent late-model mouse, and completing the first part of our Beck Racing Engines buildup, is a set of Airflow Research LT1 aluminum cylinder heads. These awesome reverse-flow castings feature oversize Manley Severe Duty 2.08-inch intake and 1.60-inch exhaust valves, 76cc chambers, and large CNC'd ports. With the addition of the Crane Cams matching valve springs and chrome-moly retainers, these heads complete the 383's long-block. Additional grinding by the head gurus at Beck Racing Engines enlarged the ports and yielded an awesome 280-cfm port volume on the intake side. The exhausts, which are perhaps the more important of the two on a supercharged engine, flowed equally well and maintained the important "D" shape.

While the cylinder heads give our late-model bruiser a set of large-capacity lungs, there's no question that its heart (and degree of power) will be determined by whatever camshaft is installed. Here, we turned to the trusted gurus at Crane Cams, who came up with a custom grind that is designed to make a ton of power and torque with a supercharger and still be civil when it comes to idling at a stop light. The hydraulic roller grind we were given has more lift and duration on the exhaust side (.352-inch at the lobe and 292 degrees of advertised duration) to help quickly scavenge the burned gasses from the forced induction. This is equally, if not more, important on a supercharged powerplant, and especially so in a street-driven environment. On the intake side, however, there is sufficient lift and duration to gulp all that the ProCharger can force feed it. Lift at the cam is a not-to-short .339-inch, while advertised duration comes in at 284 degrees. What do those lift numbers equal after they're multiplied by the Crane 1.6:1 roller rocker arms? How's .542 inch at the intake valve and .563 inch at the exhaust hit you?

Coupling the cam and crank together is the job of the Cloyes true-roller timing chain and billet gears. With a modern LT1, there isn't room for a double-roller setup or a belt drive (remember, the Opti-spark ignition resides just ahead of the chain assembly and the waterpump drive connects to a straight-cut gear on the backside of the cam sprocket), therefore we were limited to the OEM design. Not to worry, though, we've heard of some pretty powerful engines doing well on a single-roller chain, so we were confident that the Cloyes setup would take all we were going to throw at it.

The balance of the valvetrain includes the aforementioned Crane roller rockers and lifters (which, unlike the individual factory design, use a tie bar to pair them together), Crane chrome-moly pushrods and matching valve springs and retainers. All told, the components will allow our big-inch mouse to spin freely to 6,500 rpm. Keeping all of our Clevite bearings and internal parts lubricated is the responsibility of the Titan Sportsman oil pump residing in a Billet Fabrication extra-capacity aluminum oil pan. This duo has proven itself time and again, and we're sure that the oil will do its job.

While this part of our buildup (we'll offer up Part 2 next month) was intended to concentrate on the long-block machining, blueprinting and assembly, it's important to let you know that in addition to the ATI D-1 Procharger, the balance of the induction system will be as close to the original-design tuned port injection as possible. In fact, the intake itself is a factory version, with the important exception that it has been totally reworked by the experts at Arizona Speed and Marine (and further smoothed by Extrude Hone). Coupled with an Arizona Speed and Marine 58mm billet throttle body, we're confident that our 383 will have no breathing problems whatsoever. So, until next month, when we discuss how all of the external parts come together and then venture off to the Vrbancic Brother's dyno to see what she makes, follow along as we visit Beck Racing Engines for some precision machine work and assembly.

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