Monte Pilot

All - I could please really use some help here.

Last weekend my '06 TBSS' motor developed a valvetrain tick. After popping the heads off I discovered that 14 of 16 lobes were chewed up pretty good on the cam, and all of the rollers on the lifters are damaged. Some of them pretty severely.

Here's the kicker, back in 2014 I replaced the cam and lifters due to a single chewed up lifter (same cam, same pushrods, etc). The prior cam had a good 70k mi on it without any issues but for some reason I only got 40k on this one. The only upgrade I made was install some Brian Tooley Platinum valve springs to handle the +0.600" lift of the cam. Have any of you seen this type of damage before and what is the likely culprit?

Again, the only real change I made was upgrade the valve springs from the stock single-coil ones to the Brian Tooley Platinum double-spring valve springs.

Are the valve springs too stiff for this cam? Would running break-in oil and ZDDP additive help this next go around?

Here are the specs with pics to follow...

Cam:
PCMofNC High Lift Stealth Cam (215/227, .60x/.61x, @ .050″, 116 LSA)

Lifters:
LS7

Pushrods:
Trick Flow 7.400" +0.080" (7.480" total pushrod length)

Lifter Preload:
0.050"

Rockers:
Stock

Valve Springs:
Brian Tooley Platinum Valve springs
Max 0.660" Lift
155 lbs @ 1.780",
380 lbs @ 1.180",
400 lbs @ 1.130,
Coil bind @ 1.070"

Monte Pilot

Here are pics of the damage to cam and lifters:

98CayenneT/A

When you say push rods 7.4 + .080" are you saying you are using 7.480" pushrods or you have .080" preload with 7.400" push rods ?

Monte Pilot

My apologies. That's what's printed on the pushrods. They are 7.400" plus 0.080" long (7.480" total pushrod length). That was the measured pushrod length factoring in a 0.050" preload on the lifters.

07NBSChevy

iTrader: (1)

I do not understand your lifter preload. When you measured your pushrod length, what did you come up with for length at zero lash?

You say 0.050" preload, then you say 0.080" preload". I am pretty sure they don't sell 7.480" pushrods either, only in 0.025 increments. Maybe I am not understanding what you are saying.
You need to take your pushrod length that you measured to obtain zero lash, say 7.350" then add your desired preload, say 0.075", which is 7.425" desired pushrod length. You should have around a 7.400"-7.425" pushrod in there, but always measure.

7.480" (7.475") seems a bit long. You may have way to much preload causing the lifters/cam to slowly eat away at eachother.

KCS

iTrader: (20)

Probably 7.400" long by .080" wall.

Monte Pilot

Sorry - the stated "0.080" wasn't the preload but rather the extra length on the pusrods beyond the stock 7.400" - pushrod length of 7.480". This 7.480" also includes the 0.050" preload on the lifters.

But....

I think I might have found the problem.

I think what happened is back in 2014 is I measured the pushrod length with the old lifters (which were stock LS2 circa 2006) and came up with a measured length of 7.430". Then I added the 0.050" preload to come up with a final pushrod length of 7.480 ... or 7.400" +0.080".

I just went out and measured the pushrod pockets on the old lifters relative to the LS7 lifters I just took out....and the LS7 lifters are 0.050" shallower than the stock LS2 ones.

Stupid mistake in assuming I would get the same LS2 lifters I had before when you order "LS2 Lifters". So the preload was waay too high. (I'm 70% certain this is what I did back in 2014 since I ordered the pushrods and the lifters at the same time, which I wouldn't have done unless I measured the needed pushrod length which was based on the LS2 lifters. I didn't know the LS7 lifters were different nor did I have an LS7 lifter on hand. Fuuuu).

So going forward I'll order a new set of LS7 lifters, cam, and 7.430" pushrods (which I'll double check to be sure....using LS7 lifters). (7.480" pushrod length minus the 0.050" LS7 lifter pocket offset - 7.430" needed pushrod length).

Monte Pilot

Nevermind, I'm incorrect again. Just measured the pushrods and they are 7.420"L. NOT 7.480". So KCS is probably correct in that they are 7.400"L x 0.080" wall thickness.

Everything I replaced in the motor back in 2014 was the exact same as what was in there. Cam, 7.400" stock length pushrods, etc. Except the lifters I installed were the LS7 ones with the 0.050" pocket offset. So in essence my preload went from 0.050" to 0.100". I'm assuming that is too high a preload.

I'll remeasure the needed pushrod length today but I'm betting I need 7.350" pushrods.

Monte Pilot

OK. I did some measuring and here's what I came up with:


Current Pushrod Length: 7.420"
Pushrod Length to zero lash (via P/R checkers): 7.310" to 7.325"
Required Pushrod Length: 7.310" + 0.050" Lifter Preload = 7.360" to 7.375"


So based on these numbers it easy to see I over-preloaded the lifters by about 0.060". (7.420" - 7.360"). I essentially doubled the pre-load.

Odd thing is I measured the LS7 lifter cup compression and there's 0.205" of travel in the lifter. If you pre-load the lifter by 0.050" the plunger inside the lifter is only traveling 25% of its total available travel. At double preload we're talking about 50% lifter compression. By my calcs the lifter wouldn't have gone completely solid unless I stuck a 7.515" long pushrod in there.

So is 50% compression on the lifter (double preload) enough to cause this kind of damage? If this damage was caused by the lifters completely compressing and going solid then where did the missing 0.100" go that was still available in the lifter?

Either way I'll go with 7.350" pushrods which will bring the preload back to proper specs.

98CayenneT/A

I know lots of people run .075" preload including myself with Ls7 lifters and some even .100" some .050" .