Turbo 5.3 valve marks on pistons...LS6 springs not enough??
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Turbo 5.3 valve marks on pistons...LS6 springs not enough??
Hey all. I have a 5.3 with 317 heads, an 02+ LS6 cam, and LS6 springs. I noticed valve marks on all my pistons after just 600 miles of driving when I had the motor apart. I'm running a T76 turbo at 11 PSI. Car pulled strong right to 6300 RPM on the dyno so I don't believe I was getting valve float, but just wanted some opinions on why the marks are there and if I should upgrade to some PAC 1218 springs?
I would assume that a stock LS6 cam on an 8.6:1 5.3 should be NOWHERE close to making valve to piston contact. I guess it could be due to a missed shift, but honestly I think I MAY have missed a shift once, and it wasn't a bad one at all.
I would assume that a stock LS6 cam on an 8.6:1 5.3 should be NOWHERE close to making valve to piston contact. I guess it could be due to a missed shift, but honestly I think I MAY have missed a shift once, and it wasn't a bad one at all.
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See I thought of that being an issue as well, but I don't know how that could be possible since I'm using the entire valvetrain off the Z06. Only difference is the 317 heads which should be physically identical. Lifters, pushrods, springs, cam, and all spring hardware is all from the vette. You think it's possible the pushrods could be wrong? Pretty sure they measured out at the standard 7.400" if I remember correctly.
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The kit comes with everything. Springs, cups, retainers, new stock locks and seals. 219 for steel.289 for titanium retainers. Odds are its a valve float issue from a missed shift. New .080 hardened pushrods are also available from BTR and are reccommended in addition to the springs.
I would also suggest verifying piston to valve even though it is an LS6 cam. One should NEVER make assumptions about clearances in an engine.
I would also suggest verifying piston to valve even though it is an LS6 cam. One should NEVER make assumptions about clearances in an engine.
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Now thats strange...never heard that before, but I'm sure it's possible. I don't know much about the stock 243's.
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ls6 heads off a z06 (and only off a z06) have slightly longer valve stems to account for the smaller ls6 base circle while using all the same size pushrods between every engine. atleast thats how i remember it lol could be wrong
Last edited by got-a-ls1; 11-16-2012 at 09:29 AM.
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+1 to this. I'm a little surprised the motor runs well at all if the pistons were hitting the valves.
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I turned the motor over perfectly free before I initially fired it up. When I started it for the first time, it ran excellent. No noise or anything. Drove it 600 flawless miles before frying 2 pistons due to detonation. Pulled it apart and thats when I noticed it. Like I said, I missed one shift during a race I believe, but it wasn't a real high revving, limiter hitting missed shift. I'm assuming that may be what it was because not that the motors back together, I have driven it over 100 miles and it runs great. Still going to be swapping to a stiffer valve spring this winter for piece of mind.