tungstenfoot

I have a what i thought was bone stock ls6 '03 Z06 with 55k miles, last 8 digits of VIN: 35100051. I am replacing all the valve springs and seals with OEM replacements and wanted to share my findings & pics for this great thread.

1) My old springs were natural color, the new replacements (PN12625033) are blue...and are MUCH shorter free length (not compressed). .17 inches shorter to be exact.




2) Inspect your rocker pedestals! mine had a crack, cheap to replace


3) I'm extremely baffled by this one...15 of my 16 valve seals/seats had a shim on top (between bottom of spring and top of valve seal. The intake valve on Cylinder #5 did not have a shim. Below is a mock up of what I found, shown on a different cylinder. You can see the exhaust valve seal has the shim and the background (intake valve) has no shim.

I confirmed today from the dealer 2 things: this is in fact a "shim" and not a anti-coil bind bearing washer or something, its thickness was consistently .016". To further baffle me, the dealer tells me my VIN does not call for any shims. In other words, my car shouldn't have any. WHAT ? Well, I have access to a spring rater at work so I'll run some tests and report my findings. I'm hoping my test results will make sense so I know how to proceed. At this point, I'm thinking I'll get a shim for intake #5 and move on with life. I dont expect .016" to create a huge force change, but I'll be able to report on rates tomorrow.

Has anyone found original OEM shims during their stock spring swap out? Has anyone found some cylinder valves with and without a shim? What did you do? Any help appreciated...

SHIM:

ZeeOSix

tungstenfoot - my guess is you did not buy this Z06 new, but it had a previous owner? If so, my guess is someone put shims under the valve guide seal to adjust the installed height of the valve springs. The valve springs you took out don't look stock, and don't have the stock free length. I'm thinking the previous owner had some kind of aftermarket springs in the engine already.

If you bought this '03 Z06 new, then the shimming of the valve springs from the factory is a new one on me too.

04silverZ06

I'm in the market for an 02-04 Z06 - would it be somehow possible to 'peek' in the valve cover(s) to see what color the springs are?

This could help determine if that particular Z is potentially plaqued with the yellow springs?

thanks

Trash

I was thinking the same thing.

tungstenfoot

You guys are correct, i bought car used. I also took some pics and measurements using an intercomp spring rater today. There is no possible way these were OEM springs. I did get some good info , ill post up my findings in a few.

tungstenfoot

Here are my results today:

Old spring results (unknown aftermarket brand)
Free length,=2.2975"
Wire od=.164"
Weight= 72.0 grams
Force at 1.800" installed height (w .016" shim)= 124#
Force at 1.25" install height w/ shim= 275#

New oem spring (blue):
Free length=2.125"
Wire od=.167"
Weight= 82.7 grams
Force at 1.800" installed height, no shim = 96# (spec is 90#)
Force at 1.25" install height, no shim= 292# (spec is 295#)

Rates For comparison:
274.5 #/in aftermarket (measured w .016" shim)
356 #/in blue oem (measured no shim)

My results were consistent and repeatable. The pic below is the blue OEM spring at 1.25 inches, pretty much at solid length. I sure as hell hope it never gets near that point!



So now i just need to verify install valve heights are still 1.800". Since this swap is for reliability only (no plans for cam) i'll be going back and removing shims and re-installing the new blues.

Theres some lessons learned here folks!
1- if youre doin a drop-in replacement u better make sure your stuff is stock!
2- for those owners doing this swap w aftermarket, do the next owner a favor and add some notes in the owners manual and keep old parts for proof! Share the love. -wfoot

tungstenfoot

Any idea which aftermarket spring this could be?

chris crash

Would you say the GM replacement springs, retainers and keepers are safe to use to replace an original untouched engine valve train???

tungstenfoot

^^I dont know much about valve spring specs but it seems like 1.250" force is a common spec. That doesnt necessarily mean the spring sees this condition during use. As for LS6, i have no idea what the shortest compressed length is during operation. Based on the pic above and what ive seen manually rotating crank w the blues installed (w a .016" shim mind you) it doesnt seem close to that condition in actual use on engine. Long story short, i absolutely think if all is stock the OEM replacements are all good and will be for many many miles.

ZeeOSix

tungstenfoot - In Post #321, those springs you took out look like PAC 1518s by the color and how smooth the surface is. Here are some specs on PAC 1518 springs. Maybe use these to verify.

Large End OD / Large End ID (in) -- 1.290 / 0.885"
Small End OD / Small End ID (in) -- 1.055 / 0.650"
Seat Load (lbs @ height) -- 130 @ 1.800"
Open Load (lbs @ height) -- 318 @ 1.200”

Free Length -- 2.300 ~ 2.335"

The free length numbers are what I measured when I put PAC 1518s in my Z06.

ZeeOSix

Most spring makers give spring force specs at 1.800" (installed height) and 1.200".

The stock cam in the LS6 will lift the valves as follows:
Intake = 0.551"
Exhaust = 0.547"

So, if the valve spring is at 1.800" with the valve closed, it will compress to:
Intake = 1.800 - 0.551 = 1.249"
Exhaust = 1.800 - 0.547 = 1.253"

tungstenfoot

Thanks for specs. Ill check a couple more dims tomorrow, those PAC specs look very close. Do they call for use of .016" shim ?

Also for LS6 cam lift, don't we have to factor in the rocker ratio to get displacement from spring install height? Or did you already do that? Good info here, thanks again

tungstenfoot

You could try by pulling out one or two bolts on cover ( pull out with grommet too) shine a pen light and see if u can see

ZeeOSix

You might be able to get a glimpse of a valve spring with a flashlight by lookng down the oil filler on the front RH valve cover.

ZeeOSix

The PAC springs I installed had an installed height of 1.780". Only way to make them 1.800" installed would be to machine 0.020" of material off the head, and that wasn't gonna happen. I think there is a range called out in the Service Manual for installed spring height, and I was within it.

Those lift specs I gave above where at the valve, not at the cam.

tungstenfoot

Damn, so this is at the valve! Quite honestly im very suprised the spring will get compressed to the point it looks like the photo above! Actually its prob worse since it sits on the valve seal flange. Kinda crazy if u ask me but maybe these beehives have more safety margin than they visually lead me to believe. Good thing im also going back to remove shim too cus thats not helping either.

tungstenfoot

Do i have this right: the "install height " as its commonly referred for our configuration is measured from the head machined surface to the underside of the top retainer. Correct?

Its alittle funny cus the valve seals have a integrated spring seat which actually influences the amount of compression or "install height" of the spring. Im thinking the machined surface is the true reference surface, not the top of the valve seal flange.

Do i have this straight?

tungstenfoot

The springs i removed line up with these dimensions, almost exactly. Its my understanding the pac 1518s are good springs. Now i really dont know what to do...

ZeeOSix

Yes, the installed height of the valve spring will be from the top of the metal base on the valve guide to the bottom side of the top retainer. It's the actual height of the spring when installed with the valve closed. If you leave those shims in, you could cause coil bind on the springs. I would remove all valve shims. The base of the valve guide is meant to be the metal seat for the spring.

Those springs you took out (PAC 1518 possibly) have more lift potential, and therefore the getting into coil bind on the stock cam is impossible.

ZeeOSix

Did you start that test with the spring at 1.800" long in the test fixture, then compress it another 0.0551" to see where it ended up?