Concerned about the valve springs. 2003 Z06 w/33K. I can eyeball down the oil fill and see one natural colored one. 99.9% sure the prior owner did nothing other than annual maintenance...no CLB or SSE, window sticker in the glove box. Asking for reliability opinions. It's fast enough for me in stock trim, just playing around in backroads and I'm 60. I'm thinking PAC 1218 springs and putting in the CHE trunnion kit. Trunnion upgrade is probably overkill but so simple "once you're in there". I think I use the stock retainer and keepers? Of course swap out the seals. New plugs and wires. What else should I be watching for on the engine? How long does the harmonic balancer wobble before letting go? My goal is the make this engine as reliable as possible. What advise do you have for me on parts to replace or watch? Not tracked, not driven at sustained high RPM, just romped around in backroads. I've read and learned alot on this forum, greatly appreciated. The only problem I have had with the car in almost 7 years was the ABS module failed. If that happens to you, extract it and send it to the "ABS Fixer", who puts MIL SPEC parts in, and gives you a lifetime warranty. Shops will drop in another stocker prone to fail. I've asked for some help and guidance, so I wanted to share some info I learned. Thanks guys!

 

The PAC 1218 springs are a very popular option. The nitrided version should offer increased service life for peace of mind, but these springs are almost certainly overkill for the stock cam.
IMHO, there is no excuse not to replace the valve stem seals while you are in there.
I personally like the CHE trunion kit. The OE needle bearings don't much like higher than stock cam lift, or higher than stock valve spring pressures.
IIRC, the PAC springs are designed to be drop-in replacements, so your current retainers and keepers should be OK.

There is no way to predict how long the harmonic damper will last. They don't typically let go in a spectacular fashion, because they are boxed in by the steering rack in the front and the timing cover in the rear. The outer ring just tends to walk back and forth and grind a hole in the steering rack housing, or the timing cover. It's best to keep your eye on it!

If you are going to replace the damper, consider replacing the important rubber bits in the engine compartment (belts and hoses) and make sure the idler pulley bearings rotate smoothly. And, be VERY careful bleeding the cooling system! You might consider a 4-port steam kit.

 

In support of what "Tron Z" is saying I would HIGHLY recommend the Brian Tooley trunnion upgrade. They've done away with the bushing style trunnion as they can/do wear speaking from experience.
The BTR design used the roller bearings but they added an end cap so in the even that the bearing race fails they aren't able to fall out and end up potentially destroying your engine... speaking from experience again.
The installation is easy especially if you have a light duty press. A decent bench vice works ok too. I've done it both ways. You have to remove a small amount of the baffle in the valve covers to clear the slightly wider trunnions. Again it's very easy.

BTR PREMIUM LS ROCKER ARM TRUNNION KIT - TK002 (briantooleyracing.com)

 

For your use case, I'd replace the springs with new LS6 valve springs. New stock replacement Replace once and never worry about it again unless you're swapping the cam. If you think that you *might* swap a cam in the future, then the PAC springs could be worth the extra money, but definitely overkill for the stock cam.

As far as the balancer goes, it's a good idea to replace it eventually, but should you be in a hurry to replace it? Probably not if it's not wobbling or causing pulleys to chirp. Just watch it, chalk the outer ring to the inner ring and watch for movement of your lines over time. If you were to change the balancer, this would be the time to do a cam.

 

Just put the 1218 springs in and call it a day. The trunnions are fine until you run high lift cams with aggressive lobes and high spring pressures. The trunnion upgrades are over hyped. You can re-use the stock locks and retainers with the PAC 1218 springs.

I have about 10k track miles on my car over the last 3 years and rev up to 7400rpm with stock rockers and PAC 1218 springs.

 

Thanks for all the feedback. I put in the PAC 1218s. The rockers looked fine upon inspection, left alone. Fun getting #7 plug in...checked some Youtube advise that had me shaking my head back and forth. My advise...take the rubber air system tube off from the back and push it down. This will allow for a better direct shot to the plug hole. Try an old plug boot attached to the plug or use a swivel plug wrench...and do it by hand only. These guys on Youtube are using knuckles and extensions and going into ALUMINUM by tool. This is a recipe for disaster. A couple of these plugs are not easy to get back in, but you will get them in being careful and patient if necessary. I have a question...I've got an AWOL 13MM deep socket (dropped from the valve spring compressor), back of the driver's side engine bay. It didn't bounce around a bunch, it just fell it there and went "clunk" and sat down. I've been using my endo scope for about an hour looking for it. I can't believe that I can't find a tool the size of my pinky, but not luck so far. Anyone know where the burmuda triangle is on the driver's side engine bay?

 

I believe there's a wiring harness that runs up the back of the engine bay in that corner, maybe it got stuck up on that? This picture should be all you need. I couldn't find one like it anywhere else but took this while I had the motor out to do that cam.

 

Thanks. I'd been working in the garage, so I put it up on ramps outside (better light) and went on another easter egg hunt. No love, impatient after 15 mins, I went on a quick test drive, a warm up for oil change. Started to look like rain, so I put it away. Ran it again the next day and did the oil change...no tool. Started looking around a bit more, and there it was down in the wheel well area (easy to see). It must have popped loose when I drove it. I'm glad it didn't come out on the road although I'm out in the country, so nobody was behind me on these warm up runs. Glad I have the PAC 1218s in now so I can quit thinking about it!

 

Tron Z - can you elaborate on the coolent change concern? I've watched a few videos and it doesn't seem like a big deal. That said, I walked home a few miles one time when changing coolent on a BMW 330xi...

 

A swivel socket helps on 7. Long tube headers IMO actually make plug changes easier.

13s and 15s can go missing when working on C5s not just the 10mm

Things bounce when dropped and get all sorts of places. I've had stuff go down the firewall in the blackhole under the master cylinder. You can unbolt the black plastic behind the wheel house from the bottom of the car. I'd thump the plastic in hopes of hearing it before removing anything.

I've also had bolts sockets etc. get caught on top of the front subframe as well as on top of the frame. Sometimes you have to put on gloves and feel around.

 

With that low mileage and your intended use I believe you are wasting your time and money by replacing the springs and and rocker arm trunnions. Enjoy the car and leave it alone. I replaced the valve springs on my 02 Z06 only because one of them failed; my car had the yellow painted springs.

 

I would not bother replacing trunnions on a stock cam.

 

Take a look at the SPEC Corvette rules. There are some interesting upgrades allowed in their rules for reliability. The one that caught my eye was the tensioner pulley for the serpentine belt. The stock pulley is known to throw belts during spirited driving. SPEC rules suggest upgrading to the Katech pulley. Here are the rules if you're interested in looking for more tips: https://www.speccorvette.com/pages/rules

 

I liked 3.7....replacement valve springs are permitted and recommended...