Gen IV Small-Block Build - Budget LS Buildup

Mixing And Matching GM's Gen IV Parts To Build An Affordable, 6.0-Liter L92 Powerhouse

Barry Kluczyk Jun 1, 2008 0 Comment(s)
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As the number of GM's production Gen III/IV V-8s proliferates, there's been a corresponding explosion in the number and variety of engine parts released to the public. Generally, they are interchangeable, but there are significant differences, too. And while General Motors and GM Performance Parts have done an admirable job getting crate-engine versions of production motors to market, there's plenty of room for the enterprising engine builder to mix and match from GM's parts bins to build unique, powerful, and-believe it or not-value-driven combinations.

Of course, "value-driven" shouldn't be confused with "cheap," but in the realm of relativity, value can easily be assessed when judged against, say, the list price for an LS7 crate engine. For reference, the LS7 displaces 427 cubic inches (really, it's closer to 428, but who's counting ...) and is rated at 505 horsepower and 475 lb-ft of torque. It also runs about $13,000 over the counter from your friendly neighborhood dealership parts guy-who'll be even friendlier when you order one.

Closer to reality for most enthusiasts are the production-based crate engines, such as the aluminum-block LS2 and the iron-block 6.0-liter engines found in seemingly zillions of GM trucks. These typically run between $3,500 and $5,500, making them good values for those who want to simply drop it in and go.

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The used LQ4 donor motor was completely disassembled, inspected, and rebuilt. Here, after the crankshaft and main caps were reinstalled, the crankshaft gear is installed using a 2-inch length of pipe and a hammer.

The engine combination outlined in this story is based on the truck-based 6.0L (364 cubic inches) LQ4 bottom end with a set of new L92 cylinder heads and a four-barrel carburetor. The L92 heads have tremendous airflow for off-the-shelf parts and are a performance bargain from GM Performance Parts. The engine dyno-tested to the tune of 480 horsepower with GM's Hot Cam and a whopping 540 horsepower with the General's racing-derived Showroom Stock camshaft.

And the price for all this glory? About $4,300-that's LS7 power territory for about a third of the price. Yeah, it seems like a value to us, too, and it would have been even cheaper if we hadn't bought two camshafts.

The impetus for the engine came from Bob Cross, a Michigan-based enthusiast who is very familiar with all of GM's latest engine offerings. The engine was destined for a '51 Chevy truck project, and Bob enlisted the help of his nephew Steve Marsa and his friend Cliff Urmanic, who performed the assembly. Dyno testing was done independently at a Flint, Michigan-based performance shop.

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The LQ4 engine uses hypereutectic (cast) pistons that have proven to be very strong. They have a dished head that will enable pump gas-friendly compression when used with the L92 heads and their smaller combustion chambers.

Affordable, Easy-To-Build Combo
Building Gen III and Gen IV (alias LS) engines is remarkably easy and time-efficient; only four socket sizes are required to disassemble the engine: 8mm, 10mm, 13mm, and 15mm. Most of the bolts are interchangeable, too, so there's no fumbling with different-size bolts. They also use "dry" gaskets (no liquid, RTV-type sealers), and with their crank-triggered ignition systems, setting engine timing is as easy as plugging in the ignition controller.

The starting point for our value-driven 6.0-liter engine was a used LQ4 engine purchased for only $350. Most of the rest of the parts used to build up the engine were sourced from the GM Performance Parts catalog.

The L92 aluminum cylinder heads were the big enablers of the engine's admirable dyno results. They're the same heads used currently on the 6.2-liter-powered Cadillac Escalade and GMC Yukon Denali, but they are similar to the heads used on the Corvette Z06's LS7 engine. The have huge runners, 2.165-inch/1.600-inch valves, and flow a whopping 310-320 cfm on the intake side at 0.600-inch lift on the top end. They list for $399 apiece-pretty cheap for such a high-flowing aluminum head, in our opinion.




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