Originally Posted by racerx17x

what about installing a ls6 cam in a ls1 with 241 stock heads. would i use the ls6 pushrods or the ls1

Originally Posted by Dan_the_C5_Man

There are no "LS1 or LS6" PR's; GM uses the same PR for both motors.

Originally Posted by www.idavette.net

Another major difference between 385-horse and 405-horse cams is the base circle radius. The base circle for the ’01 LS6 is smaller than that of the LS1 and the truck cams and, for MY02, it’s even smaller. Most Gen III cams have a 19.7-mm. base circle but the ’01 LS6’s is 19.3 and the ’02’s is 19-mm.. Both reductions were to accommodate increases in valve lift.
We asked Jim Hicks why the base circle had to get smaller when lift increased? "All of our cams (prior to LS6) had the same base circle radius. We had a problem with that base circle, if we wanted to go to higher lifts: the nose of the cam would approach the same diameter as the cam bearing journals or even above them.

"Obviously, that means you can’t install the cam in the engine–little bit of a problem. Your only alternatives are to increase rocker arm ratio, which we weren’t going to do, or reduce the base circle radius."


The ’01 base circle reduction did not require a change in dimensions of any other valve train part, however, the 405-horse cam was a different story. "I wasn’t comfortable reducing base circle that much," Hicks told us, "without compensating for it somehow, because the position of the plunger within the hydraulic lifter is not optimal any more–you’re too high in the lifter.

"There’s different ways to correct the geometry. The one we selected to minimize the impact on our manufacturing operations was to increase the length of the valve. The valves in the 02 LS6 are 0.6-mm. longer than the valves in all other Gen III engines."

With .025-in more intake lift, the same intake duration at .050-in but a little less duration at lash and the same rev limit; something had to be done to the rest of the valve train to keep it in control at high rpm. While the ’02 exhaust lobe doesn’t have quite the aggressive profile as the intake, it’s still got more lift, so something had to be done there, too. The choices GM made were to decrease valve weight and increase valve spring pressure.

"With the higher lift, we needed to reduce the mass of the valvetrain or start getting into a float condition," John Juriga commented. "We went to hollow stem intake and exhaust valves, very similar to what we used in the ’96 LT4. We pushed the edge with a state-of-the-art, 0.8-mm. (valve stem) wall thickness–very thin stuff. The exhaust stems are sodium-potassium filled."

The ’01 intake weighed 99 grams but the ’02 weighs only 76. The ’01 exhaust weighed 86 grams but the ’02 exhaust weighs 63 grams. The exhaust stems are filled with a 78% potassium/22% sodium mix to help cool the valve. "NaK" is unstable and may spontaneously combust when exposed to air with 50% or higher humidity. Do not cut open or shorten 02 Z06 exhaust valve stems.