Pushrod length w/ LS6 cam and LS6 heads?
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I've read that installing an LS6 cam in an LS1 requires different length pushrods. I was recently informed though, that its not the case if you've installed a pair of LS6 heads. I just wanted to get this cleared up before I put the car back together...
So, on an LS1 engine, with a pair of LS6 heads (no milling done) with an LS6 cam, what length pushrod is needed?
Thanks,
-Will
So, on an LS1 engine, with a pair of LS6 heads (no milling done) with an LS6 cam, what length pushrod is needed?
Thanks,
-Will
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if the heads are off of an LS6 and have the lighter valves, then yes stock length. But if they are 243 castings off a 6.0 then they have regular valves and will need a longer pushrod to keep the geometry correct
The valves stems are longer on the lightweight LS6 valves to make up for the reduced base circle of the LS6 cam.
The valves stems are longer on the lightweight LS6 valves to make up for the reduced base circle of the LS6 cam.
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you can get whatever size you prefer, depending on how much lifter preload you are wanting and whether or not you plan on putting lifters, cam, milling, etc... Pushrod length checker, but stock will work for so many setups, you just can't go wrong with 7.400"
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#11
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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
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Originally Posted by Dan_the_C5_Man
There are no "LS1 or LS6" PR's; GM uses the same PR for both motors. ![Mullet](https://ls1tech.com/forums/images/smilies/mullet.gif)
![Mullet](https://ls1tech.com/forums/images/smilies/mullet.gif)
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True LS6 Heads have longer valves since the base circle of the LS6 cam is smaller.
Ls6 heads with the longer light weight valves + Ls6 cam with smaller base cirlce = 7.4" p-rods from the factory.
LS1 = 7.4" p-rods
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.
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.
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Okay, so i have a Trex and i'm putting ls6 heads on(unmilled) tom or sat. and wondering if i can stay with my 7.400" cause i know everyone says measure PTV. WEell, I didn;t, i jsut pulled my plugs and spun the motor easy...No issues, and i been running them for a month or two. Now with these ls6 heads having smaller combustion chamber, etc., etc. will i have issues, or what? Please don't say measure, cause i know i need to, and i know taht's the only way to tell for sure, but anyone else with this setup? What you running? 7.300, 7.325, 7.450 , what?