Katech’s Naturally Aspirated Gen-V LT1 Makes Over 800 Horsepower

Even though it’s extremely popular these days to slap some form of forced induction on an engine and make big power, it has long been said that the real measure of an engine builder is making power without boost. Enter Katech.

Deeply entrenched in the high-end LS-based motorsports market, it was no surprise that they came hard out of the gate into the LT market. “A few years ago, we developed a 427 cubic-inch LT1 that made 700 horsepower, naturally aspirated,” says Jason Harding, Katech’s director of aftermarket operations.

“We weren’t done at 700 horsepower. We wanted to go back and see how much further we could push the LT1. To do that, we developed an all-new cylinder head we’re calling the LTK.” Designing a cylinder head is one thing, building an engine to take full advantage of the new cylinder heads’ benefits is a different story altogether.

From the Top to the Bottom

Starting with the crown jewels of the engine — the LTK cylinder heads — they are cast and machined entirely in the United States and have had all of the components redesigned for much-improved performance. “This exhaust port is significantly better than the stock port. It flows quite a bit,” says Eric Weihman, one of Katech’s cylinder head technicians.

The flow numbers disclosed are 380 cfm at .800 inch of lift on the intake side, and 256 cfm on the exhaust. Besides the much-improved ports, those numbers are achieved through the use of a stout 2.200-inch titanium intake valve, and an undisclosed-size exhaust valve made of Inconel on both turbo and naturally aspirated applications.

“We did all of our valvetrain development using [the titanium intake and Inconel exhaust valves] and it passed our testing. So it can be used in both Turbo and N/A applications,” says Harding. “We may offer a titanium [exhaust valve] option In the future.”

The LTK heads — whether for a boost or N/A application — come fitted with titanium intake and Inconel exhaust valves. While the valve materials and port designs are the same between the two applications, the chamber design differs based on the application.

Moving down into the chambers of the cylinder heads, that is where there is a different between turbocharged and naturally aspirated applications. According to Harding, the combustion chambers for the naturally aspirated versions of the head are optimized for the quirks of an N/A direct-injected cylinder, while the intake and exhaust port designs are the same between the two.

Controlling the valves are a set of PAC Racing Springs dual valvesprings, which are combined with the OEM rocker arms. These heads are capable of .700 inch lift on factory rockers,” explains Eric Suits, one of Katech’s engineers. “They can handle even more lift with a Jesel or other roller-tip rocker.”

This set of heads uses the factory LT1 rocker arms. In this configuration, the heads are good for up to .700 inch of lift at the valve. With upgraded aftermarket rocker arms they are capable of more lift.

Gen-V Short-Block

Obviously, when putting together an engine of this caliber, the short-block being just right is absolutely critical. For their 427-cube mill, Katech starts with a factory LT1 engine block, which they perform their dry-sleeving process on and clearance for the 4.00-inch stroke. With the sleeves installed, Katech finish-machines the cylinders for a 4.125-inch bore.

In that block, they install a Callies Magnum-series crankshaft, made from forged “ultra-pure” 4340 steel, which is heat-treated, gun-drilled, and fully profiled. The crank is held in place by ARP main studs and Clevite H-series main bearings.

Attached to the crank are a set of Callies Ultra connecting rods made from Timken 4330V steel, also using Clevite bearings, which connect to a set of custom Mahle pistons and rings. “We utilize a custom piston because it works better with the big 2.200 [intake] valve,” says Suits. In addition to having more ideally located valve reliefs, the custom piston brings the compression up to 13.0:1.

For this, build, Katech went with the dry-sump option, using an OEM LT1 dry sump oil pan and one of its super-trick high-capacity scavenge, high-capacity pressure LT dry sump pumps, which offers up to 45-percent more pressure, and over 50-percent more scavenge capacity, while being made of 4140 billet steel to increase the pump’s durability. “With the high-RPM, getting the oil scavenged and keeping it out of windage is an important addition to the engine,” Suits says.

Using the factory dry-sump system, upgraded with the Katech billet oil pump, there is a significant increase in oil pressure to the engine and scavenging capability.

This engine retains the OEM timing sprockets, surprisingly, but doe utilized the tried and true C5-R timing chain. Katech wasn’t willing to divulge the exact camshaft specs, but Suits did mention that there was “a little more duration and a lot more lift.” To handle those increased specs, Katech went with Morel high-RPM tie-bar hydraulic-roller lifters with Trend pushrods.

Injecting The Beast

Obviously, this naturally aspirated beast is direct-injected, using the OEM LT1 fuel pump and LT4 injectors, pushing E85. “Our testing has shown E85 works great in direct-injected applications and can provide much greater power,” says Harding. “The boosted cars love the additional octane and cooling effect and this engine has high compression and can take advantage of the E85’s higher octane. Even standard compression DI engines have shown worthwhile benefit.”

On top of the engine, they tried multiple intake manifolds before settling on the Holley Hi-Ram manifold. “We ran the MSD intake, which is the standard C7 intake we use, and made 760 horsepower,” explains Suits. “Then we swapped that intake out for the Holley Hi-Ram, and that got us to 806 horsepower.”

Using a Katech 103mm Gen-V throttle body — which retains GM electronics and performs like a factory throttle body once calibrated to the ECU — on the Hi-Ram intake, the visually impressive combination performs exceedingly well in the upper RPM bands.

Katech will be offering the LTK heads by themselves, or as part of a crate engine package which will be identical to the engine featured here.

Once the combination had been tuned on the SuperFlow engine dyno, the numbers were impressive. Peak power of 806 horsepower occurred at 7,300 rpm, while peak torque of 639 lb-ft occurred at 6,000 rpm.

“While dynoing we run full accessories,” explains Suits. “There’s a little bit to be had there if someone wanted to run an electric water pump. We also run a full C7 intake tube on it as well with no bellmouth or anything on it. We run a standard filter and a standard mass-airflow sensor.”

While this configuration is Katech’s standard crate engine configuration, there are obvious points where a few extra horsepower can be extracted if you were so inclined. Either way, how often do you run across an 800-plus-horsepower naturally aspirated crate engine?

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About the author

Greg Acosta

Greg has spent fifteen years and counting in automotive publishing, with most of his work having a very technical focus. Always interested in how things work, he enjoys sharing his passion for automotive technology with the reader.
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