billla

Last night on my way home, my '03 Z started chugging and ticking from what seemed to be the right engine bank. I managed to keep it running above about 2K RPM to get it the 3 blocks home - admittedly a deci$ion I may regret.

Just going out this morning to pull codes and start looking it over, and I'll chronicle what happens.

Since troubleshooting over the Internet is such a common pastime, anyone wanna offer up a guess?

K-Spaz

I would not start the car again to find out...

billla

That was my take as well - I'm pulling the valve covers this AM.

Definitely agree that starting it this AM would be a Bad Thing

I bought replacement springs and tools last year but I didn't get to it...lesson learned

I hope it's "that simple"...

billla

Kicking myself pretty hard for sure - I had the time, all the tools and the parts...and didn't get it done. Tomorrow, I said...

Here's the culprit; I guess I won't know if the guide is messed up until I get the spring out - is there a risk that I had valve/piston contact? It didn't sound like it and the retainer is still there, but...

Black 03 Z06

Sorry for your problems. Procrastination. A nasty word in this case.

Hope no other damage was done. Luck may be on your side.

midnight01

I would also worry about the valve guide too, broken spring would cause the valve to flop around too. when you get the spring off check the valve guide.

billla

I've borrowed a borescope to have a look; far easier than pulling the head and hopefully I can see if there are any issues. If not, I'll be pulling it.

K-Spaz

Sometimes even with a borescope it's not easy to see. For the most part, broken valve springs at low rpm are not usually destructive. Now if one breaks when you're crankin on the car, yea, odds are it'll destroy everything. But at low rpm, I would expect most times to get away with it. You running the motor back up to 2K wasn't wise, but if you didn't hear something that sounded catastrophic, I think you probably dodged a bullet here.

If it were me, the heads would be coming off anyway, even if just to do the valve spring install. But that does not mean it's necessary. For me it would buy a little peace of mind.

billla

The spring install looks pretty simple; I have the CompCams tool and an air fitting to hold the valves...so "famous last words" that should work pretty well.

There's two concerns I have - did the valve get side-loaded and damage the guides, and was there valve-to-piston contact.

The guide should be easy to tell - there should be no lateral clearance.

I should easily be able to see any markings on the head of the piston - if it's clear, I feel comfortable moving forward.

I'm not opposed to pulling the heads and once I get to bare heads I may just do so...but I'm not making any decisions until I get my hands further in there. Tomorrow

CaseyJones

I went through this a few months ago. Broke a spring which allowed the piston to break the head off an intake valve and ruin the cylinder head in the process. The valve head actually was jammed back up in the valve seat sideways. Nicked up the piston a little but nothing bad enough to warrant a replacement. I was lucky.

Procrastination sucks. I think I start doing better tomorrow.

SSTG

Sorry to hear about the Springs.
I am going to replace mine to be safe. Could you please tell me the Part numbers for the tools needed to do the job?
Also, are you using the PAC or GM springs?

Thanks!

K-Spaz

I don't have the press/scale to check the springs for the install so I generally take them to the local engine shop and let them set up the springs. I like them shimmed so the pressure is equal. Not to say that's necessary, but they do it so cheap it ain't worth my time. For that, the heads come off. I also don't have the installed height gauges though I could probably make one easy enough. I just don't want to. Some stuff I simply have no desire to mess with. This is one of those things.

If you're not gonna spin the motor real hard all the time, I don't suppose the springs need a lot of setup. Keep all the shims where they are and stick the new ones in.

billla

Had to take a few days off, but I'm hard at it today.

Doing the CompCams LS trunnion bearing upgrade "while I'm in there" since I had the kit. The Summit tool for this makes it a snap - I finished all of them in about 30 minutes with no issues. About half of the stock bearings fell apart when pressed out; form your own judgement on whether this was due to the pressing process or...not.



The engine is stock and will stay stock so I can't see the benefit of spending a ton of time on installed height and/or spring pressure. I do have the "meh" spring tester from Summit and they were all within spec - good enough, I think. Different deal on a GEN I or something built or making more power.

Ordered the FEL PRO head gasket set today along with their head bolts; thought about ARP bolts but again - seemed like overkill for $200 more.

The only special tools needed to my knowledge are the valve seal tool (Kent-Moore J-42078) which I bought from eBay for like $10, and an angle torque fitting for the head bolts that was $15 at NAPA.

I'm using the replacement stock ("blue") springs.

billla

Intake is off (for the oil pressure sensor "while I'm in there"), all the plugs are out. The plugs look good, if old - no indication of anything on the plug from the affected cylinder.





Good God, why are these plug wires so *_%*_@*)(#@ hard to get off??? Then there's that last intake bolt....!

Zero sideplay on the affected valve and action is smooth; I'm comfortable that at least the valve guide isn't damaged though it doesn't really say anything about piston contact.

Decision point now on removing the heads; I'll have the gasket kit on Thursday. It's a really tough call - it adds at least a day to the job, but I sure don't want to do this all over again right after starting it. Also, I've had some overheating issues...so maybe that's worth going through.

Question: Anything else that I should be considering "while I'm in there?"

Also curious about the valvetrain - I carefully kept everything in order, but other than the pushrods, this wouldn't seem to be required. The rockers are identical and non-adjustable, and the pedestal mount doesn't appear to be precision-ground or have any shims. The pushrods I could see as that would be the way to adjust preload...but wouldn't they have some type of identifying mark on them? How would they measure the preload during assy?

Thanks!

neutron82

you might want to reconsider those comp trunnions, this is what mine looked like after ~10k miles





I replaced them last week with a kit from a company called straub that uses bushings instead of needle bearings... if you decide not to pull the heads I would do a leak down/compression test on at least the cylinder with the broken spring to make sure the valve is seating properly

billla

What did Comp have to say about that failure? The wear pattern is odd; on some it looks like the bearing was skewed...who did the upgrade and how?

I haven't heard any other reported issues...searching I found a few anecdotal c-clip failures...but those could have been install issues.

neutron82

I talked to comp and sent them pics but have not heard back from them yet... I installed them myself when I did the cam... I had never heard about these failures either until another member mentioned it to me and posted this link, http://ls1tech.com/forums/generation...nion-kits.html ... read through that thread, apparently it isn't uncommon for this to happen

billla

Honestly, there's more hype there than anything on that thread...and all of the engines are highly modified. Not disputing that it happened, but I am wondering about the context. One guy was running springs that were 195#/400#...which is a very different animal.

Were you using stock springs, stock cam?

neutron82

pac 1518's and cam is not stock, there's no way I was going to leave those in my car after seeing what they looked like... I was just trying to give you a heads up though, good luck with the repair

billla

Thanks; stock springs and cam so I'm confident that they'll be OK. I guess we'll see

Seeing at the end of the thread where folks are finding bushing material in their oil filters...