What happens when GM Performance Parts teams up with a loyal, experienced doorslammer racer to prove the mettle of its new LSX protg? More than anything it becomes a lesson learned, a lesson that can be passed on to LSX aspirants as gospel. in this case, Robin Lawrence's Nova runs the NMCA Nostalgia Pro Street class.
This current 440.180ci version arrives at its displacement via a 4.185-inch bore and a 4.00-inch stroke. Previous experiments were conducted with a 454-inch LSX equipped with much-modified C5R castings (complete with welded-on tabs at the bottom of the heads). Now it seems as if they were a stop-gap measure that proved inappropriate for the combination and seriously reduced the swept area, requiring massive work on the piston domes to overcome.
The C5R heads were used simply because no other GMPP parts were capable of supporting the power and torque levels Lawrence sought (900 hp normally aspirated). Though he could have gone to the aftermarket for the heads he needed, the edict was to use GMPP castings, period. Those pieces are now readily available, and the new engine has a completely different combination. The only items carried over from the 454 to the 440-inch version were the Dailey Oil Pump dry sump system, Stef's pan, MSD ignition, roller lifters, springs, retainers, keepers, and head studs.
Of much more importance is the stuff that got changed and why. Up first, the valve lifters were allowing oil to pass above the camshaft oil galley because the base circle on the original 55mm camshaft was too small to get lobe lift. Hence, the lifter bodies dropped below the oil galley. Changing to the 60mm camshaft required a block with a raised cam bore (0.078-inch) and lifter bores (offset drilled) that would accommodate 0.941-inch tie-bar rollers, and a custom Lunati grind (282/304 degrees duration, 0.970-inch lift at the valve, and 114-degree lobe separation). This stick was designed by Harold Berkshire with a tighter lobe separation as well as a smaller duration on the intake lobe. He increased lobe lift by about 0.005 inch. A (standard) 9.26-inch-deck LSX engineering block was machined (any CNC-equipped shop can do this) to accept the larger diameter camshaft.
A Lunati 4.00-inch stroke forging is teamed with 6.062-inch GRP aluminum connecting rods fitted with 2.100-inch bearings, rather than the 1.88-inch bearings used previously. Trend wristpins hold the 14:1 Diamond pistons that are circled by Hellfire ring packs (1/16-inch top). For a little more squeeze on the lower end, Lawrence increased the main stud diameter from 10 to 11 mm.
At this point, GMPP requested that Lawrence work with one of its developmental partners, Thomson Automotive in Redford, Michigan. Brian Thomson and his guys have extensive experience with LS engines and felt that they could extract important information from his experimentation by bringing the program to someone local to the GMPP engineers.
High-horsepower lessons (930 on nuts) learned with the 454: The 41/8-inch stroke crankshaft was flexing at high RPM. Lawrence consulted with many crankshaft experts and got different suggestions from each. Some suggested a center counterweight. Another felt that extra bearing clearance would help. In the final analysis, he reduced the stroke of the crankshaft. With the original combination, because of the bore spacing on a small-block, the area from the main journal to the rod journal is small. As you increase the stroke or the distance, you have less material. Lawrence felt that a 2.100-inch rod journal as well as a 4-inch stroke would increase rigidity.
Further, the center main bearing was being wiped on both edges, and the No. 2 and No. 4 mains were wiped on the inside toward the center of the block by crankshaft deflection. Pistons rocking in bore caused the area above ring land to contact the cylinder wall as well. To work with the C5R heads, the piston required very deep valve reliefs and ultimately made it too thin above the ring grooves. Finally, the combustion chambers (30cc) were too small for the swept volume. Initial calculations had the compression ratio close to 18:1. The C5R heads were developed for the Corvette road race program, and as such they were on an engine that was about 100ci smaller than the 454. With the swept volume of the 454, it required serious cutting on the pistons.
For the 440 combo, Lawrence was able to use the new GM Performance Parts LSX454DR (drag race, PN 18166979) or LSX454CT (circle track, PN 19166979), with an 11-degree valve angle. Since this is an ongoing experiment, initially the engine will run the CT castings. Both versions of the cylinder heads feature a 5/8-inch deck thickness and will accommodate valve springs to a diameter of 1.66 inches. They come with CNC-machined intake and exhaust ports (313cc and 116cc, respectively) and 50cc CNC'd combustion chambers. Compared to the C5R head, intake and exhaust ports have been raised 10 mm. The Pro Power Part titanium intake valves are 2.20-inch, and the exhausts are 1.65-inch stainless.
Thomson's John Lahone made several other changes intended to improve the durability of the engine. He switched out the low-tension oil rings to standard tension and reduced the number of gas ports from 14 at 0.062 inch to just six at 0.050 inch. In discussions with Diamond, it was agreed to make some changes in the piston design based on the knowledge gained from the previous engine. Diamond reduced the diameter of the ring land to reduce the tendency of the area to rub if the piston rocked in the bore. Diamond also tightened up the contact points to give the piston some added support.
Changing over to the LSX heads required new Diamond pistons, Lunati valve springs (410 lbs/in on the seat and over a 1,000 lbs/in wide open), Trend 3/8-inch, 0.065-wall, double tapered pushrods, and custom Jesel shaft rockers with a 1.80:1 ratio. Raising the cam 0.078 inch necessitated a longer belt for the drive system. There is none available, so an idler pulley was used to obtain the correct belt length.
Lawrence: "During testing earlier in the year, we had used a nitrous jet that was several sizes smaller than rules allowed, but with the numbers we'd seen we knew that the car would run a decent quarter-mile. NOS's Monte Smith is our juice consultant. Smith wanted to make a change in the tune-up. With our progress and the bad air, he definitely gave us something that would step us up. This time we ended up qualifying seventh with a 7.79 at 179 mph, but lost in the first round running a 7.77 at 177 mph. The loss was actually a win for us. We came away with the fastest LS nitrous car in the country, confirmed when we learned that the best time to date was in the 8.20s."
On the engine dynamometer, the LSX 440 posted a nuts-only 830 hp at 8,200 rpm and 620 lb-ft of torque at 6,200 rpm.
The thing to keep in mind is that Lawrence's combination will be ever-changing. Ostensibly the car is an NMCA Nostalgia Pro Street racer, but it is actually the consummate test mule for GMPP LSX products. Certainly you'll be seeing more of these pieces in upcoming issues of Chevy High Performance.
What We Did
Examine a built LSX
This 440ci small-block proves a modern day powerplants can make power!
|Transmission||Liberty Equalizer clutchless five-speed|
|Clutch assembly||Billet, fully-adjustable Clutchmasters/Ace 8-inch twin-disc assembly and a Ram 10-inch twin-disc assembly (10-inch for testing only)|
|Bellhousing||Browell Bellhousing, SFI 6.3|
|Driveshaft||Mark Williams 4-inch-diam. Duraclan metal matrix, 1350-series U-joints|
|Rear axle||Quartermax 9-inch Fab-kit housing assembled by Team Z Motorsports|
|Centersection||Strange Engineering Ultra aluminum pumpkin, spool, 4.57 or 4.86:1 gears|
|Axleshafts||Strange 40-spline gun-drilled|
|Steering||TRZ rack conversion|
|Frame||2x3-inch rectangular tube back-half|
|Rollcage||Team Z-built chromemoly 25.2-spec|
|Spindles||TRZ 2-inch drop|
|Control arms||TRZ tubular, upper/lower|
|Front shocks||TRZ/Strange double-adjustable|
|Rear shocks||Strange coilover double-adjustable|
|Traction||Quartermax four-link, wheelie bars, antiroll bar|
|WHEELS & BRAKES|
|Brakes||Strange four-piston Race, Strange master cylinder, front/rear|
|Front wheels||15x3.5 Weld Racing Alumastar 2.0|
|Front tires||15x4 Nitto Drag 1320|
|Rear wheels||16x15 Weld Alumastar Pro|
|Rear tires||33x16 Nitto Drag 1320|
|Gauges||Auto Meter full-sweep electric|
|Wiring||Spaghetti Menders installed by Bob Keith|
|Steering wheel||Grant with Strange Engineering quick-release hub|
|Data logger||Auto Meter 32 Channel|
|Fire system||Safecraft 10-pound bottle|
|Wheeltubs||Kirkman Composites carbon fiber|
|Bodywork||Stretched rear wheel openings|
|Body panels||VFN Fiberglass fenders, doors, decklid, bumpers, hood, VFN carbon-fiber hood w/ Kirkman Composites/QuarterMax carbon-fiber scoop, Pro Glass Lexan windows|
|Paint:||Corvette Millennium Yellow wrapped with resin-impregnated vinyl GMPP graphics|
|Ignition||MSD Digital Programmable 7531|
|Nitrous controller||NOS Launcher|
|Fuel system||Aeromotive A 2000 fuel pump, JAZ 3-gallon cell|
|Cooling system||Meziere Pro Stock radiator with integral water pump|