With a hydraulic roller, the...
With a hydraulic roller, the valvetrain is critical. D&A used GM hydraulic roller lifters from the Cadillac CTS-V race program, along with COMP pushrods, Harland Sharp rockers, and Lunati dual springs, retainers, and keepers. Valves measure 2.165 inches on the intake, and 1.600 inches on the exhaust.
While the fuel side of the engine management can be readily done away with in favor of good old-fashion mechanicals, the ignition side is another story. Though it is true that a distributor can be adapted, the better solution is to retain the coil-on-plug ignition, but run it via an aftermarket stand-alone ignition control. Here D&A went with the MSD 6LS Ignition Controller, which takes input from the cam and crank sensors to operate the ignition through a fully programmable module. Andy spoke favorably of the unit: “It is a simple setup; it’s easy to play with and easy to tune. It makes setting the ignition timing fun instead of aggravating.”
Topping the intake manifold...
Topping the intake manifold is a Holley 750 HP, a unit that was customized by D&A Machine Shop. The carb proved itself on the dyno, delivering more average power than a larger 830-cfm Holley carburetor.
This hot LQ4 combination was put through the wringer on D&A’s dyno, looking to dial in the power. On the dyno, the engine was equipped with a set of Hedman Husler headers with a primary tube diameter of 2.00 inches, and a beltdriven electric water pump arrangement. With the conservative cam duration, the engine idled good enough to be at home in a hot street machine, while the cam’s tight 108-degree lobe separation provided an impressive performance bark. The goal was to dial in the fuel and ignition settings, looking for maximum average power over the entire rpm range. The Holley 750 HP was tested against a Holley 830 carb, and interestingly the smaller carb proved to be better overall. On the other hand, the engine seemed to favor a larger 3.50-inch header collector, in comparison to a 3.00-inch piece. Tuning the ignition timing proved to be critical in getting the best from the engine, and here the MSD ignition controller excelled.
With the final dyno printouts in hand and the engine cooling on its stand, the numbers told the story. The short-cammed, big-cube stoker delivered tire-melting torque from the word “go,” showing 530-plus lb-ft right from the jump at 2,500 rpm. From there the torque just ramped upward, peaking at 581 lb-ft at just 3,200 rpm. While the low-rpm torque peak might imply that the engine would quit early, the torque just seemed to plateau, holding over 500 lb-ft all the way up to 6,000 rpm! Peak power was recorded at 588 hp at 5,800 rpm. If you are looking for wild torque, and power that keeps coming, A D&A Machine Shop stroker LQ4 will dish out the numbers.
With these high-ratio aluminum...
With these high-ratio aluminum roller rockers, clearance at the valve cover rails becomes an issue. Some simple clearance mill work solved that issue. A set of ProComp tall valve covers provide for the increased height requirements.
Up front, parasitic accessory...
Up front, parasitic accessory drag is reduced via a remote electric water pump drive. A PRW vibration damper controls the crankshaft harmonics.
A GMPP two-plane intake manifold...
A GMPP two-plane intake manifold directs the combustible mixture. Andy relates that this intake manifold is excellent as delivered, with very good port alignment. Minimal massaging of the manifold was required.
A set of Hedman Husler headers...
A set of Hedman Husler headers route the exhaust. D&A experimented with both 3- and 3.5-inch collector sizes and found the larger diameter to offer an advantage.
An MSD 6LS Ignition Controller...
An MSD 6LS Ignition Controller directs the signal to the coil packs to provide the spark requirements. Inputs here include the OEM crank and cam sensors, while the software provides full ignition curve tuning capabilities.
A clever set of coil pack...
A clever set of coil pack covers clean up the engine’s visuals, invoking a humorous play on Don Key’s name.
On the dyno, this engine based...
On the dyno, this engine based on an LQ4 iron truck motor put down some serious steam, with 581 lb-ft on hand at 3,200 rpm, and 588 hp at 5,800 rpm
With torque in abundance and...
With torque in abundance and a healthy power curve, team members Donny Key, Andy Key, and Jonathan Korynosky have every reason to be proud of their Chevy LS combination.