Thread: Blower CAM spec
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Old 01-14-2020, 08:08 PM   #8
oldman


 
Drives: SS 6 speed of course
Join Date: Jan 2016
Location: Hilo, HI
Posts: 4,137
lift is one part (the most important) in the longevity equation. IMO 75% of engine failure is due to valve bounce. What causes the valve to bounce? higher lift, faster ramps (cam motion is know for gentle ramps and they grind BTR's stuff), dual springs vs conical vs beehive vs single (conical wins), RPM. For me my LS7 lifter failed on the intake IMO, it was a combination of 6800 to 7000 RPM shifts, upto 12 PSI of boost and a fast ramp profile causing the intake valve to bounce and / or lifter to fly over the deceleration ramp of the intake cam lobe. I can actually see impact wear on the flank side of all intake lobes. So if every thing stays in contact and I'd be checking or replacing valve springs every 20K miles. IMO I should have been OK, but nope.

I'm at sub .600 lift on a cam motion cam and Johnson lifters (should have got the bars). I will change springs every 40k miles, I'm on 8 or so of PSI now too. I lived through the LS1 valve train wars and unfortunately I'm doing it again on the LT1, this time around everything is the best from C5R chain, to Manley valves. I'm not risking anything like trunnion bearings or my hollow stock valves falling apart or anything. I'd even change to a real oil pump if one was made. I could get away with less stiff springs but I figure my sub .600 lift is cutting down on peak open pressure and I don't think it is spring pressure perse that is killing the valvetrain, I think it is bounce so I stuck with dual .660 lift springs just because I want the valve and lifter not to be in free float EVER.
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Forged short block, large duration sub .600 lift Cam Motion cam, 7200 RPM fuel cut, Pray Ported Heads, 3.85 pulley D1X, stage II intercooler, DSX secondary low side, DSX E85 sensor, Lingenfelter big bore 2.0 pump, ported front cats, 60608 Borla, LT4 injectors, ZL1 1LE driveshaft and Katech ported TB, ported MSD intake, BTR valvetrain, ARP studs, ProFlow valves, PS4 tires.

Last edited by oldman; 01-15-2020 at 01:48 PM.
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