The Chevy Small Block LSX Engine - This Thing's Loud! Plan B

A 1.9hp-Per-Cubic-Inch LSX Lesson

Ro McGonegal Jul 1, 2009 0 Comment(s)
0907chp_01_z Chevy_small_block_lsx_engine Performance_engine 1/19

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.

0907chp_08_z Chevy_small_block_lsx_engine Main_oiling_system 8/19

Because of the revised priority main oiling system on the LSX block, the front cam thrust plate is unique. Jesel has made some changes to ensure adequate lubrication to the thrust surfaces, milling these slots in the trust plate as well as the cam adapter. Jesel also now uses a bronze thrust washer between the cam adapter and thrust plate.

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.

Quick Notes
What We Did
Examine a built LSX

Bottom Line
This 440ci small-block proves a modern day powerplants can make power!

Cost (Approx)
$35,000

Nova Specs

DRIVETRAIN
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
Shifter Liberty Equalizer
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
CHASSIS
Front subframe Stock
Steering TRZ rack conversion
Frame 2x3-inch rectangular tube back-half
Rollcage Team Z-built chromemoly 25.2-spec
Spindles TRZ 2-inch drop
Front springs TRZ/Strange
Control arms TRZ tubular, upper/lower
Front shocks TRZ/Strange double-adjustable
Rear springs Strange
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
Parachute Stroud
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
INTERIOR
Gauges Auto Meter full-sweep electric
Wiring Spaghetti Menders installed by Bob Keith
Dashboard Covan insert
Seats Kirkey
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
BODY
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
EXTRA
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

Sources

Auto Meter
Sycamore, IL 60178
866-248-6356
www.autometer.com
Lunati
662-892-1500
www.lunatipower.com
Strange Engineering
Morton Grove, IL 60053
847-663-1701
www.strangeengineering.net
Motive Gear
Chicago, IL 60609
800-934-2727
www.motivegear.com
TRZ Motorsports
Kissimmee, FL 34744
407-933-7385
trzmotorsports
Diamond Pistons
Clinton Township, MI 48035
877-552-2112
www.diamondracing.net
Holley Performance Products
Bowling Green, KY 42101
270-781-9741
http://www.holley.com
Thomson Automotive
Wixom, MI
248-349-0044
www.thomsonengines.com
Team Z Motorsports
Taylor, MI 48180
(734) 946-RACE
http://www.teamzmotorsports.net
Browell Bellhousing
765-447-2292
www.browellbellhousing.com
Jesel Inc.
Lakewood, NJ 08701
Daily Engineering
daileyengineering.com
Liberty High Performance Products
libertysgears.com
Pro Power Parts
prrpowerperf.com
Pro Systems Racing Carburetors
prosystemsracing.com
Quartermax
quartermax.com
Stealy Performance Machine
stealyperformance.net
Stef's Oil Pans
stefs.com
Trend Performance Inc.
trendperformance.com
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