There’s a muscle-bound world of used engines out there just waiting for deals to be made, but you should tread carefully to avoid being bitten. Efrain Diaz recently bought what appeared to be a really great deal on a used Katech LS7 engine. The previous owner was honest—his engine had been rode hard and hung up drenched multiple times and was nearing the point where it would need a rebuild. But Efrain opted to run the engine in his yellow ’69 Camaro for some events in the Optima series before doing a teardown.
After a season of more track thrashing, Efrain took the engine to EVOD Garage in Escondido, California, where engine builder Chris Pollock discovered this rehab was perfectly timed. There were a few damaged parts, but thankfully the rotating assembly was in good shape. Pollock suggested a complete rebuild for the LS7. His initial discoveries included a broken pushrod and lifter. This is not unusual since the LS7 was built to take advantage of a higher peak engine speed. It’s generally accepted that the pushrods on even a stock LS7 should be one of the first things swapped out for no other reason than the 0.080-inch wall performance aftermarket versions are much less prone to deflection and failure.
The next discovery was a hydraulic roller lifter that was trying to push its roller axle straight out the side of the lifter. The lifter bore prevented this cataclysmic event from occurring, but ended up requiring a sleeve. Other damage included loose/worn valveguides and a couple of titanium intake valves that would have to be replaced due to advanced stem wear.
Once the Katech short-block was fully disassembled, the only other surprise was a scored oil pump and the center three main caps appeared to have moved around a bit as evidenced by fretting between the main caps and the main web. With the block cleaned, the machine shop performed a simple line hone, after adding ARP main studs, which brought all the main caps into alignment. This also made setting the main bearing clearance easier. After the crank was polished it was time for reassembly.
Katech’s original pistons employed a gold-coated anodizing that did a great job of preventing wear in the piston ring grooves so the pistons were retained. For a better seal, EVOD selected a Total Seal 1.0/1.0/2.0mm ring package that ensured the cylinder pressure would remain in the cylinder where it will do the most good.
The heads were also slightly abused and required a solid cleaning followed by replacing several of the titanium intake and hollow-stem exhaust valves that revealed excess wear. The new valves were matched with new guides and the heads were checked to verify the installed height of the new valvesprings.
Because this engine would see plenty of abuse both on the street and on road courses and autocross tracks, Pollock spec’d a custom Comp hydraulic roller grind using a 235 at 0.050 intake lobe with 0.610-inch valve lift. The cam basically adds roughly 20 degrees of duration to both the intake and exhaust lobes while moving the lobe separation angle closer together. Factory GM cams for all LS engines tend to be very wide, which reduces the overlap and contributes to a very smooth and stable idle, which is important for a stock factory engine.
Adding duration tends to shift the torque curve higher in the rpm band as evidenced by this engine’s 6,600-rpm horsepower peak. It’s interesting that the stock LS7 cam makes peak torque at 4,900 as did the new, longer duration Comp version. However, the factory LS7 peaks at 6,300 with 505 hp and this new combination cranks the power up to a much stronger 661 hp at 6,600 rpm. This can be attributed to both the added duration and the tighter lobe separation angle.
One of the more interesting ways to evaluate an engine’s power curve is to see how far beyond the torque peak the engine carries maximum torque. One way to do this is to use the 90 percent rule, where we judge the power based on seeing how far beyond the torque peak the engine will maintain at least 90 percent of the peak torque. With a max torque of 585 lb-ft, 90 percent of that is 526 lb-ft of torque. Looking at the power curve, the LS7 is exceptional since it maintains no less than 526 lb-ft of torque from 3,800 to 6,500 rpm. This produces the somewhat flat torque curve you see in the graph.
This makes for a very tractable engine that is smooth and easy to apply the throttle because the power is always there. To put this into perspective, we plugged the power curve into the Quarter Pro dragstrip simulation program. In a 3,500-pound car with a five-speed manual trans, 3.55:1 rear gears, and a really sticky set of 26-inch tall tires, this package has the potential to run 11-flat at 128 mph! This simulation is designed for drag cars, so a Pro Touring car would likely be a bit slower, but low 11’s at 126 are certainly possible. That’s pretty stout for a street engine on pump gas.
While the LS7 isn’t nearly as common as 6.0 and 6.2L engines, it wouldn’t take much more to upgrade an LS3 to nearly these power heights with similar parts. Of course, the edge would go to the larger displacement of the 427 LS7 and the high-rpm potential afforded by parts like the titanium rods. But, with 661 hp potential from a naturally aspirated engine on pump gas these are great days to be a Chevy guy!
The following specs compare the original factory LS7 cam to a new custom grind that Pollock selected. This is worthy of attention since Comp can very quickly and easily build almost any cam you want based on selections listed in the Master Lobe Profile catalog that’s available online. In this particular case, Pollock selected a grind with an even greater spread between the intake and exhaust and also tightened the lobe separation angle (LSA) from 121 to 113 degrees. This increases the overlap and will add torque in the midrange and additional peak power, but comes at the sacrifice of reduced low-speed torque and a rougher idle.
|Camshaft||Dur. at 0.050||Lift (inches)||LSA|
|GM LS7 intake||211||0.558||121|
|GM LS7 exhaust||230||0.558|
|Comp intake 13047R lobe||235||0.61||113|
|Comp exhaust 3663R lobe||258||0.596|
|Main Parts List|
|ARP main stud kit||234-5608||Summit Racing|
|ARP head stud kit||234-4317||Summit Racing|
|ARP rod bolts, LS7 2000-series||234-6302||Summit Racing|
|ARP crankshaft bolt||234-2504||Summit Racing|
|ARP-stainless accessory bolt kit||534-9605||Summit Racing|
|Comp cam, custom grind||54-000-11||Summit Racing|
|Comp dual valvespring kit, Ti retainers||26925Ti-KIT||Summit Racing|
|Comp short travel, tie-bar lifters||15956-16||Summit Racing|
|Harland Sharp 1.8:1 roller rockers, LS7 offset||SLS78A||Summit Racing|
|Clevite rod bearings||CB663P-1||Summit Racing|
|Clevite main bearings||MS2294-1||Summit Racing|
|Clevite cam bearings||SH2125S||Summit Racing|
|Fel-Pro MLS head gasket, left 0.053"||1162L053||Summit Racing|
|Fel-Pro MLS head gasket, right 0.053"||1162R053||Summit Racing|
|Melling oil pump, LS7||10295||Summit Racing|
|Total Seal piston ring pkg 1.0/1.0/2.0mm||CS1124125||Summit Racing|
|GM titanium intake valve, 2.200"||12591644||Summit Racing|
|GM exhaust valve, sodium-filled||12618110||Summit Racing|
|FAST LSXr intake, LS7||146202B||Summit Racing|
|FAST 50-lb/hr injectors||30507-8||Summit Racing|
Photos by Steven Rupp