mikezohsix

I have a 2003 Z06 - LS6 - with about 20k miles. I bought the car with about 7500 miles on it in 2005. As far as I know the engine is stock except for CAI and a predator tuner. Never had any issues with the car, but it had more "sewing machine" noise than some other cars.

I changed my valve springs to PAC1218 as a preventative measure and now have significant valve train noise, almost a light knock around #2. I've removed, inspected and re-torqued the rockers once, and replaced the #2 springs with what I took out, all no help. I can hear it when on a lift under the car, but if I put a stethescope on it, I can't hear it at all in the pan or sides of the block.

I haven't gotten a real LSx builder to listen to it, but one local speed shop heard what I hear and said it didnt sound right.

For now, I need to know the specs on the stock springs so I can compare to the PAC1218 and also the lift on the stock cam. I'm now wondering if my car may have a non-stock cam and already have had different springs installed.

I measured the pushrod movement as best I can with a dial caliper and got around .320 on the exhaust and .345 on the intake. Is that sound right, figure pushrod movement should be the same as lift?

The new springs are about 3/8 taller than the stock spring. Does that make sense for what I thought was a pretty much direct replacement spring?

One other thing. I measured about 3/4 turn on all the rockers on the right bank from finger tight on the bolt to snug. One thread I read said they try to set the preload at 1.5 turns. Could I not have enough preload on the lifter?

I know I'm all over the place, but I don't want to pull the heads and throw lifters at it, or, pull the cam to see if it's going away. Just looking for some ideas....

CHADsterss

Bent pushrod or a lifter may have crapped out on you. Any way you could post a video of it so we can hear it?

therabidweasel

iTrader: (5)

Stock cam specs are easily found, I'd tell you if. Knew off hand, but easily searched.

The lift you measured at the pushrod needs to be multiplied by the 1.7 rocker ratio to arrive at the stated lift on the cam card.

3/4 turn is pretty light for non-sgort travel lifters. that's 30 to 45 thou I believe...you loose 8 of that heating up.

A video would be helpful.

mikezohsix

here are two pics of the springs.
from the car on the left, PACs on the right.

No marking on the OEM springs, no stripe or color as is often shown for the LS6 spring. Do some come without any marking?






I'm really wondering about pushrod length now, though don't understand why the springs would exagerate noise since nothing else changed.

I did find the specs on the LS6 spring and they're 90 pounds with the valve closed which is 40 #less than the PAC, about 25# valve open. Also my cam doesn't line up, but that that's probably my measuring being off - will try to get a dial indicator.

mikezohsix

can those springs be stock with no color or marking?

z28241

iTrader: (13)

Dont think their stock, pretty sure most LS6 heads had yellow springs..

99Bluz28

iTrader: (35)

Definitely not stock LS6 springs, from 0-lash to 22ft.lb. you'll want 1.25 turns to put you right about .060 preload.
BTW, insufficient preload with stiffer spring will be louder.
So how do your PRs look, and are they stock?
I'd go up one size in PR length that'll give you the need preload.

Cam specs
204/218 .551/.547 117.5 LSA

Vexzer

iTrader: (1)

My valve train was very noisy with high-cam & HD springs. That lasted 5-7 K miles before a stock lifter failed. The moment you hear an odd screech or squeal shut it off immediately. The noise is the roller skidding on the cam. Not trying to jinx you & I hope you never hear it. I replaced cam with same Futural & lifters with stock, same HD springs, 20K miles ago with no further trouble
The noise you hear could be piston slap. Nothing really wrong at all until 80K miles later it begins slightly using a little oil.
Find out if cam is stock or not. Then use appropriate quality springs.

mikezohsix

here's what I accomplished today...
-went to the machinist I've used for 25 years, Precision Automotive in Simsbury CT. super nice to deal with.
- measured my original springs and the PAC1218s and they were both right about perfect on spec.
- he listened to my car, really was thinking it might be an aftermarket cam because they're more noisy. definately heard what I heard, and didn't hear it on all cyl.
- hooked me up with an ex-chevy dealer mechanic.
- went to see him, another nice guy. he thought maybe rocker arm bearings, suggested I move some around.

- pulled the rt valve cover and pulled one pushrod. measure 7.390 end to end (flat to flat). no markings on the pushrod, spherical on both ends.
- checked pushrods for flatness, they're fine.
- set it up so I could run it with the valve cover off.
- listened to each rocker bolt and heard the most noise on cyl 4 and 6.
- moved the rocker from 4e to 2i to see if the noise moved, it did not.
- checked again on the lifter preload and get 3/4 turn between finger tight and snug, before you start torquing.
- looked at the valve stem wipe pattern on the rockers I pulled and it looked smooth, no roughness, to it.

I took these video's...
(sorry, couldn't embed the video for some reason)

pushrod preload


side to side motion on rockers that are on the base circle


decent video of the sound that I'm after


put the stethescope ear piece on the mic for the camera. you can sort of see my hand going from rocker to rocker. you can definately hear the difference from one to another.


OK, so what do you all think should be my next move. I'm thinking of putting the original springs back on the right side. After that, what do I do?

anthony.fatica

iTrader: (10)

Sounds like the same noise I have...Does it get louder when giving it light or hard throttle but barely noticable if at all when giving a steady medium throttle?

old93camaro

iTrader: (8)

sounds like you have a blockage on some of your push-rods, have you tried some b12 down the push-rods and lifeters to see if you can clean them a little? Even some sea-form may help you out

vettenuts

iTrader: (4)

I also posted on CF, but I didn't see a lot of oil coming out of the rockers while it was running.

As for preload, I get 0.059" of lifter preload based on your 3/4 turn from zero lash to rocker bottoming.

mikezohsix

I hear it most at around 1500 on a steady cruise, but that's when the exhaust is most quiet. I would not say that this is throttle or load related.

Everything is spotless in the motor, but blockage may be an explanation for the onset of the noise. What is b12?

there's 40# oil pressure at idle at 200 degree oil temp. All the oil flow is very even, I don't know what to compare it to for flow though.

mikezohsix

oil flow video

[url]http://www.youtube.com/watch?v=sxmLnTE5Kgw&feature=share&list

old93camaro

iTrader: (8)

B12 Chemtool Carburetor Cleaner, its a video floating around where a guy shows how to use it. He had a tick on like one or tow rockers and used it and it went away.

CHADsterss

To me it sounds like your pushrods aren't the right length.

Vexzer

iTrader: (1)

If you haven't changed the oil in a while, do so and cut the filter open & look for sparkles, if you have the old filter, cut it.

crainholio

iTrader: (2)

Video of the very unorthodox but effective lifter cleaning technique on an LS engine:

mikezohsix

well, another day on the car:

- I replaced all the valve springs with the originals
- I checked all push rods to check that they're clean
- I checked all the PR for straightness
- I checked the length on all the PR, 7.380 end to end on the flat spot
- I measured each cam lobe - see table in picture. I couldn't measure the valve throw because the lifters dift down, got a number right off the pushrod, so you have to multiply by 1.7. I made the steel dial indicator stand so tall so it would sit over the rockers, thinking I could measure the rocker tip movement.
- I checked to be sure all the valves were the same height with a Staratt straight edge - all within .003"

What did I learn?
- push rods are fine
- all the springs look fine
- I have a 2002 or later Z06 cam, which I expected
- all the lobes are withing a thou or two of spec, which is about as good as I could measure because of angles of the indicator and not having a good tip to catch the top of the push rod

I looked at the rockers and there is play in the fulcrum. No looseness or roughness, but definate play. See the video.

I ran it briefly, will run it longer tomorrow and make a call on any difference in noise. I will pull the mag plug and cut open the oil filter tomorrow.

Shots of the dial indicator sitting on my new steel stand so the mag base has something to "stick" to.





Here are the cam lobe throws, for all the lobes, and the value multiplied by 1.7 to match the cam spec 547/551



a shot of me hand cranking the motor thru a cam lobe stroke on an exhaust lobe

http://youtu.be/6XsDWqpwQl0

and heres the question of the night...
is the motion in the rockers, they're all about the same, right?

http://youtu.be/yhWh52HYDRQ

dirtbag

iTrader: (2)

I haven't read the entire thread and you may have already but I would get an adjustable pushrod length checker and find the size you need. Measure from zero lash and the base circle on cam and add in your desired preload, done. Order some custom length pushrods from Manton. Also, my rockers have some play in them like yours so I will be making the switch to comp cams trunion bearings. Hopefully they are tighter than the stock rocker bearings.