Engine is stock with 50K miles. Installed PAC 1211x springs and did the CHE trunnion replacement. I don't recall hearing this much noise before parts changes, but I did the install just after purchasing the car, so I don't have a before, but I don't think it was this loud. I can hear the "sewing machine noise" even at low speeds cruising through town with windows up and A/C on.

I called CHE and was told that I should have checked rocker geometry after trunnion install even though their instructions do not state this. He told me I could use a screw driver to isolate the loud rockers, then buy .025" longer pushrods and install as needed. I questioned that and he said I may need .025" longer or .025" shorter depending on how geometry checked out. Wow. I'd love an engine with 8, 11, 14 different length pushrods.

Anyway, I made quick vid and you can hear the normal injector noise, but valve train noise most notable at 1,500 - 2,000 RPM. Sounds like my SBC 383 with flat tappet hydraulic Comp Cams XE with aggressive ramps, full roller rockers, etc. If I had those parts, I would not be concerned. You Z06 guys consider this noise normal?

 

going to get a lot of options but since the pitch noise is changing on a steady rpm something is wrong. I don't think it s the pushrods. Take covers off see if rocker arms are loose.

 

I installed the Straub Technology bushing kit in my car, and while the "sewing machine tick" is still there at idle, as soon as I bring the RPMs up a couple hundred over idle, my car quiets right down. I seriously doubt that there is a large enough market for these bushings, such that there are a number of manufacturers of them, just 2-3 shops making them, with a bunch more selling them.

A) I personally think that your valve train appears to be unusually noisy, unless it's a bunch of questionable fuel injectors; B) does the noise quiet down at all if you bring up the RPM?

 

At what RPM would things quiet down? In the vid, I held engine at 1,500 for a few seconds then around 2,000 and it was not getting quieter.

 

Can't help you on the noise, but I can tell you on two different C6Zs that I have owned , I added the CHE bushed rockers from CHE and then installed by a LS specialist shop , both were much quieter than before the install. I have been completely happy with them.

 

In my case, they quieted down at around 900-1000 RPM, although my engine is nowhere as noisy as yours. I'm suspicious that you have some other issue....What's your oil pressure, and also, what weight oil are you running?

 

Just checked oil pressure at idle. Engine cold with oil temperature of 88- 43 PSI. Running 5 30 Mobile 1. I do not recall exact number hot but seemed normal to me.

 

I dont think it has anything to do with the CHE trunnion kit...

You put a spring in there with 130 in. lbs. of force installed(1.8"). The factory springs are 80 in. lbs. installed(1.8"). Compressed your springs have 370 lbs. of force and factory has 294.

You are hearing the valves slam shut with 60% more spring rate.

The CHE trunnions are not really a cause, but since they have no slop or really way to absorb any of that "shock", so to speak, its louder. My guess is had you gone back with the factory trunnions you STILL would hear this ticking.

Any reason you jumped up your spring rate that much? Factory cam? Planning to go bigger cam in the future?

 

That may be it. I went with that spring because that is what PAC recommended for my intended use- track (with street use as well). They said that spring was suited for tracking the LS6 and would provide good high RPM stability. Factory cam and I don't plan on changing that anytime soon.

 

Meh...

GM "blue"(they arent blue anymore BTW) springs would have also been fine probably. I dont think they have shown any bad tendencies at the stock LS6 redline, at least not that I have read about. Now if you are tuned and pushing another 300-500 RPM then yea maybe a little more spring is warranted, but at stock redline of the LS6 the GM "blue" springs seem up to the task.

I guess I am not a fan of really high rate springs unless you need them for a specific purpose.

With a high rate spring you will also kill lifters at a faster rate. GM lifters are **** to begin with add on a much higher rate valve spring... keep an ear on them.

 

Whoever told you that you can change the rocker arm geometry with different length pushrods doesn't know what he's talking about. You can do this on the Gen 1 SBC, but NOT the LS engines. I used to think this way, too, because I hadn't thought about it long enough. Different length pushrods in an LS engine do nothing more than increase, or decrease, lifter preload. The reason you can't find anything about rocker geometry in their instructions is because it won't matter what you do with pushrod length.......

 

Update. I upgraded to slightly longer BTR 7.400" pushrods, with a tad more preload (0.075") and that made no difference in noise.

I then removed the PAC 1211x springs and installed 1218x springs. The 1218x's have 10lbs more seat pressure, but open is 328 vs 370 compared with the 1211x. Spring rate is significantly less as well at 313 vs 385. I also switched from 5-30 to 0-40 oil.

The noise... Slightly reduced. I'll chalk the noise up to "normal" for this engine and still much less than my small block with aggressive flat tappet cam, roller rockers, etc. I'll sleep better with the lighter spring rate lol.

Again, the trunnion upgrade was my initial concern because CHE said more noise would be notable until pushrods were updated.

Wanted to update/close this out so that people would not be left hanging. Thanks for the input everyone.