It was only a few years ago that even a 500hp street engine was newsworthy. The fact that Thomson is explaining why his engine "only" makes 770 horses on the street demonstrates how far we've come with LS engines and tuning. Of course, we can't discuss a 770hp, 840 lb-ft, LS9-blown engine without bringing up cost—and this one tallies a pretty strong price tag of around $35,000. Thomson doesn't dance around the cost. It is what it is.

"The LS7 and LS9 parts aren't cheap, so it's an expensive engine to build, no doubt about it," he says. "But more than simply a great dyno number, you get an engine with excellent, factory-quality drivability. We put a similar engine in a car last year and did more than 3,000 miles on the Hot Rod Power Tour with the A/C on and didn't have a lick of trouble."

Installation of the engine may require some mild fabrication to accommodate the unique LS9 accessory drive system and its wider belt, but hood clearance shouldn't be an issue on fullsize GM trucks and SUVs.

Installation details notwithstanding, the engine's dual-purpose performance—dependability with tire-shredding power—reinforces the Jekyll-and-Hyde personality of Thomson's LS7/LS9 hybrid. It's the sort of monster we'd like to have lurking beneath the hood of our favorite Silverado or maybe an Escalade that would shake up the country club setting; Quiet and unassuming one moment, and a terror the next. That's the way to keep the other guy guessing.

Dyno Chart
RPM LB-FT HP
3000 807 461
3100 814 480
3200 822 501
3300 826 519
3400 829 537
3500 831 554
3600 833 571
3700 837 590
3800 839 607
3900 842 625
4000 844 643
4100 843 658
4200 841 672
4300 839 687
4400 834 699
4500 826 708
4600 817 716
4700 807 722
4800 796 727
4900 786 733
5000 771 734
5100 759 737
5200 749 742
5300 740 747
5400 731 752
5500 723 757
5600 717 765
5700 707 768
5800 697 769
5900 683 768
6000 672 768
Peak numbers in bold.

SOURCE
Thomson Automotive
Wixom
MI
248-349-0044
www.thomsonengines.com