Chevrolet Performance hydraulic roller lifters are designed as direct replacements for your engine. These lifters were designed for use by GM to be used in performance engine builds and incorporate improved valving to allow higher rpm capability.


With its 600lb-ft capacity rating, Tremec's TKO-600 has been a popular choice for use with a high-performance V8s. Our past experience with the TKO-600 has been nothing but positive. The gear ratios offer excellent acceleration and performance while reducing cruising speed to improve economy and reduce overall engine wear. Some hobbyists find that the TKO-600 doesn't always shift smoothly when operating near 6,000 rpm. That wasn't typically an issue since most Pontiacs built with stock components didn't operate at such speeds. Aftermarket components have pushed the operating range and power output beyond the capacities of the stock TKO-600, and that can be concerning to some.

The 600Xtreme Upgrade

American Powertrain picks up where the highly capable TKO leaves off. Its 600Xtreme TKO option increases the torque capacity of the TKO-600 by 350 lb-ft and improves shifting up to 7,500 rpm. And it accomplishes it without compromising synchronization or shifting performance at low speed.

"We didn't want to take anything away from the basic goodness of the TKO, which is our bread and butter transmission because it is so capable right out of the box," explains American Powertrain owner Gray Fredrick. "Our goal was to tweak the box to get every bit of performance possible from it without negatively affecting driveability."

So what makes the 600Xtreme special? Starting with a new TKO-600, a single American Powertrain technician in its craftsman-type shop completely disassembles and reassembles the transmission to ensure the build is consistent and thorough from start to finish. During disassembly, the parts are separated and sorted into those that are reused and/or reworked from those that are replaced.

The existing 4616-alloy gears, shafts, and shift forks are exchanged with identical pieces that have been cryogenically hardened to improve strength and performance. The controlled process includes slowly reducing the components to 300 degrees F for more than 12 hours with liquid nitrogen to improve molecular consistency, adding as much as 30 percent more strength to the original alloy without affecting its tolerances. "We specify that our parts be rapidly brought to a high temperature to maximize the effects of the cryogenic hardening process," Fredrick adds.


The optional billet-aluminum White Lighting shifter features a short throw and adjustable spring bias that can alter the centering rate with a quick turn of an Allen key. The Revolution shifter stub is easily adjusted to fit any original Pontiac console.
Once the hardening process is complete, the gears, shafts, and shift forks are REM-polished to a chrome-like finish— it's a micro-process that smoothes the contact surfaces of a component. It serves to improve the tolerances between components and eliminates the micro recesses on the gear faces, where transmission fluid can get trapped and pressurize as the gears mesh. "That can reduce efficiency and create noise," says Fredrick. "REM polishing also reduces parasitic loss, increases durability by reducing heat and friction, and reduces gear noise from the already-quiet helical-cut Tremec gears."

Improved strength is only half of the equation with the 600Xtreme. The TKO is factory synchronized for shifting speeds at or slightly above 6,000 rpm. While a quality clutch and pressure plate assembly, and smooth operating linkage, can increase that slightly, shifts above 7,000 rpm generally require additional work, and American Powertrain tends to the entire shift mechanism for clean and precise shifts at all speeds.

"The TKO-600 is an internally-shifted gearbox, and it uses linear solid-steel shift rails and lugs within the transmission to switch gears," adds Fredrick. "The durable rods are constantly lubricated and do not bend or deflect like common external-rail shifters. With the 600Xtreme option, our technician hand-polishes each of these components to remove any rough edges that could create binding while shifting. The internal springs are also swapped for higher-rate units to improve the shifter's rotational return rate."

The 600Xtreme transmission is carefully assembled to what American Powertrain calls "race tolerances." Some of the small parts are upgraded during assembly, too. "The plastic shift-fork pads, which are quite suitable for everyday use, are replaced by solid bronze forks that will survive the abuse of aggressive shifting. Standard sprung-steel roll pins are replaced with hardened steel pins in many locations, and original stamped-steel slider keys are replaced with units constructed of solid billet steel."

Once completely assembled, the enhanced TKO-600 is quality-tested for leaks, shaft endplay, shift quality, and in a few other critical areas. The job is then signed off on by the assembler, who assumes full responsibility for the quality of the transmission build. American Powertrain installs the appropriate performance shifter and ships it to its customer for installation.


 LS Series retrofit trunnion kits are the answer for LS engines with higher lift camshafts and heavier than stock valve springs. These trunnion bushing kits are designed to maximize peace of mind by completely eliminating the needle bearings and providing maximum lubrication to the trunnion while also providing maximum load carrying capabilities many times greater than needle bearings. Installed $350NZ

Johnson hydraulic lifters are the best you can buy. Capable of 9000RPM

If you want more than a stock LS engine I can supply parts with a used engine you buy or pull it all apart and it new upgraded parts.

All dollar amounts are guides not fixed quotes.


An Asian made chrome-moly forged crankshaft is not only way stronger but can increase the cubic inches of a 6.2L block to 429CID (7041 liters).

While factory LS3 rods are plenty strong with an increase in stroke length you want longer rods and aftermarket are stronger.

Again you can buy rods made in Asia, you know where, or American crank and rods for twice as much.

A Lunati crank made overseas cost $1250NZ and their American made version for $3250NZ.

Rods, $850NZ from China, $2380NZ for America.


If you swap the crank you'll be changing the camshaft and lifters.

If the motor has AFM or VVT that will get tossed out. 

Maybe $750NZ


Next up would be CNC porting the heads $1350NZ.

Competition a valve job and resurfacing $525NZ.

Better valves and springs, depends, say $600NZ.


The intake manifold.

Truck manifolds make more low RPM power than car manifolds.

Most aftermarket manifolds will only increase power above 5000 RPM.

The FAST XFI will improve power everywhere.

The new Holley Twin Throttlebody Crossram Sniper makes the most power increase under 4000RPM. $2600NZ with TBs.

Switch to a carburetor is also an option.


Labor for making modifications is a lower cost than NZ shops charge.