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!