NightmareTA

iTrader: (20)

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.

LilJohn

Were the heads milled any?

Snag a kit from Brian Tooley Racing... better spring than the PAC's imo.

jridenour31

I definitely wouldn't be running stock springs, especially with that much boost.

T76s10

iTrader: (6)

x2 on the brain tooley springs. very nice

NightmareTA

iTrader: (20)

Heads are not milled any. And I have never heard of that name before...interesting. I'll have to check them out. I'm just concerned with being able to re-use all my old hardware, like pushrods, locks, retainers, etc.

T76s10

iTrader: (6)

the springs come with retainers and locks. their $219 from tick performance. is it possible that your pushrods are too long? maybe you should invest in comps pushrod tool to double check

NightmareTA

iTrader: (20)

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.

LilJohn

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.

WheelsUp84z

iTrader: (14)

could also be detonation. Valve float is possible, and even tough you shouldnt assume clearances, I highly doubt the PTV clearance is anywhere close to tight with unmilled 317's on a 5.3 and such a small cam.

slowride

iTrader: (3)

What valve hit? You have the springs that match the cam NA, but I wouldn't run boost with it without more spring pressure. You don't have the light titanium intake valves either.

T76s10

iTrader: (6)

I don't think it could be a pushrod issue then

one fast zo6

iTrader: (490)

i also think that stock ls6 243 heads have shorter valves

NightmareTA

iTrader: (20)

Now you've got my attention. How would detonation cause a valve to hit a piston?? Reason the motor was apart was because I replaced 2 pistons due to cracked ringlands...but still not seeing the connection here with them hitting the valves.

The intake valve on every cylinder slightly hit. And yea I'm thinking more and more about just throwing on some heavier springs for piece of mind. Not like they're that expensive.

Now thats strange...never heard that before, but I'm sure it's possible. I don't know much about the stock 243's.

got-a-ls1

iTrader: (12)

ive had great luck with my 1518s even at 8500 rpm mis shift stock pushrods didnt bend, no marks on the pistons. the rod bearings... well not so happy.

got-a-ls1

iTrader: (12)

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

427

iTrader: (3)

Check your clearance, valve springs won't cause intake valve issues.


Kurt

sweet99ss

iTrader: (41)

Thats weird especially with the low comp ratio

killernoodle

+1 to this. I'm a little surprised the motor runs well at all if the pistons were hitting the valves.

NightmareTA

iTrader: (20)

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.