Here is what I can tell you.

My whole strategy was to build up a very streetable car that a C6 ZO6 owner could never outpower without having to tear down hisstock rotating assembly and rebuild the bottom end. This was a challenge at the time because no one knew exactly what would be in the C6 ZO6 -- most people bought the rumor of three-valve 6.6 liter engines\ with variable valve timing, but I correctly guessed GM would go with 427 cubes and what are basically C5R heads. I assumed one could put up to 5-6 lbs boost and get about 650 RWHP from that stock engine so my goal was 700+ RWHP with docilte streetability.

The block is a C5R block bought from GMPP. List was about $8-$9K but I got it for $5K.
The engine was built by Charlie Hempfield, who lives near here. I didn't know him but he had a good rep: he built a Daytona winning engine for Hendricks sometime in the 90s ('96 I think) and did the engine for the Martinsville polein 2005,and was NASCAR Truck Series engine builder of the year a couple of years ago. He agreed to build the engine for a reasonable fee ($5K plus he buys all the parts and I pay full retail) because he had never worked on "one of those LeMans engines" and wanted to see what it was about. He took a full year working on it part time which was another part of the deal. ((His overall verdict is that it was one hell of an engine but not durable -- "It'll last through a day of hard racing but it would nevermake it througha full season."))

Target compression ratio was 10:1 - high enough for good NA throttle response but low enough to permit much more boost that 11:1 or higher ratios.

Crank and rods are Crower: again hempfield order the parts and tested and machined them so I don't know the particularly model #s. Pistons and rings are by CP, and custom made to a design Hempfield had patented--I recall they are super-light and Hempfield told me they were the weak link in the engine but would be "bulletproof to 800 HP or more."
The engine uses the piston to center the rods, something Hempfield does in most of his engines, which results in lower oil pressure but that is fine, he says (runs about 29-30 lbs at hot-oil idle and45 at 3K RPM. The piston tops are dimpled (supposed to be worth 10 HP).

Unlike the LS7 my engine has a wet sump and I had an MTI ported/reinforced oil pump. Subsequently there were higher capacity aftermarket pumps in aftermarket but I still have this one: would like more flow though, but I hear there are incompatibilities with these aftermarket pumps and double-roller timing chain.

Cam: I experimented with a lot of them -- a Lingenfelter and an MTI which produced 525 NA, but finally went with a custom grind Crower made, .595 lift and only medium overlap - lots of low end and mid range torque, smooth stock like idle at 950 RPM, great street/traffic driving, and only 512 RWHP NA, and let the SCr do the work in the top of the RPM band.

Patriot Level III LS6 heads with further porting and polishing by Justin Engineering (now defunct I hear) and 2.08 inch intake values: at the time I bought these outflowed anything else available. Ported L92 heads from the LS6 might be better than these today (I'd hope so with their 2.2 inch intake valves).

Jesel Pro-series shaft mounted rockers with Crower pushrods and roller lifters. High rise rocker covers by Katech - had lots of problems getting these to fit well, and had to grind out the inside metal to get them to clear the rockers on the intake manifold side.

Fast 90 mm and throttle body. Kocks 1 /7/8 headers, stock oil pan, "re-adjusted" oil pan baffles to clear the stroker crankshaft. Aftermarket dual core radiator with oil cooler (takes about 5 lbs oil pressure).

Upgraded 18 volt fuel pump (Lingenfelter), very big injectors can't remember what but it had Ford green tops on it and they proved not big enough. Some sort of "impendance translator that amplifies the stock injector signal for these very big injectors (cost about $1100, can't remember much more now)

ATI Procharger D1SC with only the standard 6-rib belt. 8 rib wasn't available but could be preordered at the time but not sure I would use it: fitting both the dual core radiator and the SCR proved a challenge: the SCr's intake filter is right up against a stock radiator - it took some doing to getthe SCrto co-exist with a radiator that is just that tiny bit wider through its core, and I'm not sure we could ever find the additional 3/16 inch needed for the 2 additonal ribs. The two intercooers are under the headlights.

The Procharger proved a big headache. First, ATI recommended pulleys that were way too big and we spent days futzing with progressively smaller pulleys before we got anything good:currently using a pulley that would give 16- 18 lbs on a stock LS6 but with the larger displacement and betterbreathing it gives only 8 lbs on my engine. Second, with the SCr working hard, the idler tensioner plate warped under full throttle and kept throwing the belts. This is a well know weakness in Procharger P and D1 models. We waited for an A&A Corvette's upgraded plate forever and have nad no problems since. Also,the higher belt tensioneventually shattered the alternator bracket. and made a mess under the hood. GM made a running change to the bracket sometime in the 2003 timeframe. Earlier alternator bracketsare cast ina U shaped channel -- later ones have a full four side box cross-secton for greater strength: you can tell by turning over the bracket (they look the same from the top) -- the older weaker one you can see the bracket has the U crossection.
The engine eventually produced 670 RWHP at 7.5 lbs with good street manners from pump gas. We added the methanol to cool the intake charge as much as anything and somehow it made boost go up just a bit and we got 703 RWHP. There is about a pound or two of additional boost left I can get with this SCr and the 6 rib belt before I get belt slip, maybe another lb or two beyond that with the 8 rib belt, but its fast enough on the street as it is. I have the Lingenfelter mini-tube kit and run 345 drag radials on the rear but its just wheelspin in the first three gears anyway.
Best thing I did was pay Carolina Auto Masters something like $1500 to really tune the car well: not just re-program the ECM on the dyno at max power, but they spent a whole week with it - John Creech drove it to and from home every day with a laptop logging everything and tuned it for cold idle, warm up, and docile street manners. It does drive like stock, expect it does not like to run smoothly at low RPM in air below about 35 degrees.

 

Thanks Lee for the write up. I know it took some time to do. We are getting a new Z06 soon and plan on possibly putting our D1-SC on the car, with some mods to the motor of course. Should be pretty fun. Do you autocross any? Reason why im asking, Im in Tupelo Mississippi and our club will be putting on an autocross in October at the Tupelo Regional Air Port. For any that have been to our event it is known as the "Hot Pursuit" We usually have a great turnout. We would love for you and any friends you have up there to come and join. Ill let whoever is interested in the event know more details as it gets closer. Thanks again.

 

There's ALWAYS someone with more power. When they finally do show up, it's tough to swallow. Power, in any form, corrupts - you gotta' have more, and more, ...

My sister picked up the GTO for '06, with the 405 hp motor. I told her a year ago that she'd be wanting more soon. 6 weeks ago, she said there's some new comparable GM vehicle (GTP?), or something like that) with 425, or close, and she's checking into it. She accused me of power seekin', since I had an '87 L98(), until I told her that my '02 1ton had more power.

Someone will sooner or later show with more scoot. The more $$$ you spend, the more it hurts. Do body mods to stand out.





You near the trianglein NC? I'm 60 miles east... Had the bulk ofservice contracts in that area. Still do some work in the area...

 

Yeah, I'm in the Tirangle - I live in Cary and work near Rex Hospital just off 440 Beltline in Raleigh.