Les is more! We had great...
Les is more! We had great expectations that our first LS engine build would be successful, and 560 hp and 510 lb-ft is plenty strong for a pump gas performer.
If you recall, last month we yarded a greasy, iron-block 6.0L from the people at LKQ and proceeded to bolt in a Scat stroker 4.00-inch-long arm, Scat I-beam rods, and a set of Mahle forged pistons. To keep it simple, we pitched the EFI in favor of an Edelbrock carbureted Victor Jr. intake, a Holley carb, and an MSD ignition conversion. When the carb cleaner fumes hit us, we decided to name the engine Lester Scruggs (L.S., get it?). The goal last month was to show how easy is it to assemble one of these engines. If this is a taste of future horsepower and how easy it is to make, we're all for it.
This month, we bolted Lester to Ken Duttweiler's engine dyno and unleashed the hounds to measure how much twist came out of the other end. Secretly, we thought 575 hp on pump gas was achievable from our iron 404. But we compromised the compression a little because we also want to bolt on a blower in the near future, so now we have to live with 9.8:1. We still made an impressive 560 hp, so now our rally cry is, Les is more!
The big leverage point for the LS series of engines has always been excellent cylinder heads. Every LS production head features no worse than 15-degree valve angles (the standard small-block Chevy valve angle is 23 degrees), and more recent LS performance variations have pushed that out to 12 degrees. So our testing started with a bone-stock set of 6.0L heads. Our pal Richard Reyman at West Coast Racing Cylinder Heads (WCRCH) cleaned the original heads and pronounced them fit for duty with new seals and a set of Comp beehive valvesprings. Next, Reyman suggested testing a set of his CNC-ported production 6.0L heads as a simple upgrade that would retain the cathedral-port-style heads.
Our ultimate goal, however, was to test Lester with two different sets of L92 heads. For those of you not familiar with GM engine nomenclature, the L92 variable valve (VVT) timing engine first appeared in the '07 Escalade and is now used in many current SUVs and trucks. Bolted to a 6.2L engine with a 4.03x3.62-inch bore and stroke, L92 heads are prized for their very large, rectangle-shaped intake ports connected to huge, 2.165/1.590-inch valves. Because of the oversized intake valve, these heads can only be used on 4.00-inch-and-larger-bore engines, which makes them perfect candidates for Lester's 4.010-inch bore.
We've included the flow bench numbers for all four sets of heads so you can follow the bouncing ball through the whole process. After our testing, it appears the stock L92 heads may need some additional help on the exhaust side for ultimate power. Even without porting, these heads offer excellent power potential. Our pals at Scoggin-Dickey sell them for just under $900 per pair, but you will also need the L92-specific rockers, stands, and bolts to make it all work, which will up the price to just under $1,200. That's a screamin' deal.
With all this going for these heads, we had to try them. You may recall we've tested these castings once before. Back in the May '07 issue ("550 HP for Under $4,900") we ran a set on a stock 6.0L short-block with a Comp hydraulic roller cam, a single-plane intake, and an MSD ignition conversion. As the headline reads, we made 551 hp at a somewhat stratospheric 6,800 rpm. We figured if a 364ci engine could make this kind of power, then adding another 40 ci would make a lot more. Our results were a little different than we'd expected, but still rewarding.