what rockers to go with spinning 7400rpms
01-12-2009, 07:11 AM
#1
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what rockers to go with spinning 7400rpms I finished my 370 build for N20 I have a custom cam with a 645 light hyd rollar. The car when tunning spins 7200 without thinking twice I have brand new GM rocker in now. Any thoughts and how many rpms with the stock rockers take.
01-17-2009, 07:48 AM
#3
Mine have seen 7800 a couple times. I'd try to keep it under 7500 just because the hydraulic stuff starts to get a little unstable at that kind of rpm.
General rule of thumb 7500 and under hydraulic and stock rockers are fine, if you want to spin it higher then that, you're in solid roller territority.
Sure there's always someone that has done this and that and gotten away with it, but for max reliability, that's a good rule to follow.
General rule of thumb 7500 and under hydraulic and stock rockers are fine, if you want to spin it higher then that, you're in solid roller territority.
Sure there's always someone that has done this and that and gotten away with it, but for max reliability, that's a good rule to follow.
01-17-2009, 08:37 AM
#4
TECH Fanatic
The lobes need to be chosen for their "kindness" as well as lift and duration, the springs and retainers should be the lightest and lowest load that will get the job done, and the pushrods must be very stiff. The rockers need to be light, stiff and have a low moment of inertia. The stock rockers fit that bill admirably. Aftermarket roller rockers do not.
7800+ has been done with a valvetrain like I described above. No problems in a season of racing.
You might check with your valvetrain designer, or if you don't have one, check with one who has done the 7800+ HR stock rocker and lifter thing successfully. He should be able to advise you. It's not rocket science, but it is all about physics.
Jon