Z.06

Driving home from a trackday yesterday, rolling along backroads at 2000 rpm, my 2008 Z06 developed some valve train-type noise that I have never heard before. The engine kept running, but sounded like one cylinder might be gone. Fearing a broken valve spring (I have dual spring PAC 1208x) or a rocker arm that has lost its needle bearings, I kept the engine speed as low as possible on the remaining 30 mile drive home. I had to stop for gas, and the engine didn't want to idle normally. While at the gas station, I opened the hood and there appeared to be more noise than normal coming from the passenger side valve cover. There were no messages on the DIC, and all of the gauges were normal. No oil smoke, etc.

This morning, with the engine cold, I removed both valve covers and could find nothing amiss. I pulled off the rocker assemblies, which are OEM, and everything seemed 100% normal. I checked each pushrod for straightness. I looked at the valve springs the best I can and did not find any broken ones. One cannot see the inner springs very well though.

Part of my dilemma is that I was planning to install a pair of AHP heads in a month or so, going with the Moldstar 90 guides and PSI 1515 springs. I can proceed to do this now, but would feel better about it if I understood what my problem was yesterday.

Could I have a lifter problem? a cam problem? The cam is a Comp grind which has been doing fine for the last 15,000 miles. Cam specs are 228/248 degree on 114 with lifts of .623/.652 at the valves. Lifters are OEM with 28000 miles on them.

Any thoughts about what else should be checked?

LS1Steve

Praying to the small block gods for ya!

Reminds me of a time this exact situation happened to my LS6 (in my gen1 CTS-V). After not seeing any red flags under the valve coves, I ended up pulling out the plugs with the intent of bore scoping the cylinders, and when I did, one of the electrodes was broken apart and had experienced some clear impact. Long story short the heads came off and it ended up being a crack ring land on a piston. Hopefully not your case. So, I'd suggest pulling plugs and seeing what you see. Does the exhaust smell? (as if it is burning up a lot of oil?)

jayyyw

Could have wiped a cam lobe. Those PAC 1208x springs have some pretty high spring pressures. Bad thing, if that's true, you continued to drive the car like that. Most likely sent metal particles through the entire engine.

Unreal

1208 is WAY WAY WAY too much pressure for a stock lifter. I bet you wiped a lobe and took out a lifter. Stop driving it, as you are just damaging the motor. At this point probably want to pull to check oil for metal. If lifter is wiped, time to pull the motor for a complete refresh as you gave it a nice metal sanding from the inside out.

Z.06

Well I can only hope you guys are wrong while I do the checking on the lifters. Perhaps a warning needs to go out to other past customers of Lethal Racing in Lafayette, La. They are the ones who picked this combination of cam and valve springs and elected to stay with the stock lifters in exchange for my good money. They called the cam their Phantom Cam, although there is nothing Phantom about it; it does not idle like stock. Lethal Racing was a Senior Member of this forum until 2015 and I know that they have installed this same cam in other forum members cars. I think it is likely that they were using the same valve springs in all of their installs. I tried to talk them into using PSI 1511 springs with the cam, but they would not hear of it. I believe they are no longer in business, at least under the Lethal Racing name.

My car was not smoking at all on the way home. Since my rocker arms are all removed, the car is obviously not being started or driven.

Che70velle

03BlkZ

Subscribing for results. Praying for ya OP!

JesC6Z

73DBG

Les

Mordeth is a gift to the forum. It's hard to adequately describe his worth here.

Good luck OP. About 1.5 years ago I had my heads looked over right before my extended warranty expired- for the second time, my guides were out of spec. During the head replacement process (AHP w/ Moldstar 90), it was discovered that one of my lifters and cam lobes were getting unhappy with each other. The surfaces were just starting to degrade and, if not discovered then, this would have caused me a lot of grief. I'm hoping that, if this is your problem, you caught it before things got torn up. I hate to hear that you were taken down the wrong path on your engine build.

pcguy2u

Z.06

Still doing the teardown to get the heads off and check the lifters. I'm figuring the lifters are all toast from the excessive spring load, and depending on how bad the lifters look, the cam may be toast with a wiped lobe as well. I will definitely be doing a Blackstone Labs and maybe cutting open the filter as well. Where can I get a decent filter cutter that will not put debris inside the can?

Before all this started, I was planning on installing AHP heads with Moldstar90 valve guides and tumbled Ti inlet valves with Ferrea hollow exhaust valves in October. Springs were to be PSI 1515ML with Ti retainers, all set up by AHP. Plan was to keep the same cam and use uncut head castings to get the same compression ratio as what I have, and keep my current tune. My cam specs are in the original post. Would new stock lifters be OK with this combination or what is recommended?

If my cam is toast, I will look for one with less aggressive ramps, and no more lift or overlap than my current cam. This means I have to retune, which I am less than enthusiastic about. It took 3 tuners to get it right the first time around and the only shop that did a good job has gone out of business.

Z.06

New discovery. I just reviewed my bill from Lethal Racing and it does not specify the valve springs at all. The springs are part of their Phantom Cam kit, which uses the cam specs listed in the OP. For years, I thought that I have the PAC 1208X springs because that is the box that Lethal Racing gave me my OEM springs and retainers back in. So what springs are currently in my engine? Haven't a clue. They could be 1208X springs, but they also could be something different and Lethal just put my OEM springs and retainers in the first empty box they found. Does anyone know the spring wire diameter for PAC 1208x outer springs? I can get my caliper on that.

03BlkZ

Just a suggestion. I know you said that it didnt appear to be a a broken valve spring but some people would probably say 15k miles on your springs with that cam would be too many miles. Maybe one of the inner springs are broken.

03BlkZ

I would still do the heads anyway regardless of the issue you are having.

pcguy2u

Don't know what filter you're using, but most filters can be cut with a box cutter and a small hammer...

heavychevy357

Z.06

Well heads are off. All of the lifters would slide out save one and it has been beaten out on the bottom so it cannot come out the top of its bore. Cam lobe is damaged anyway, so it looks like the approach will be to remove the cam with the engine in the car, and slide the lifter out the bottom of the bore. We will jack the engine up and clean out the oil pan, interconnecting lines and oil sump tank as best we can. May put on a new oil pump if we cannot be sure the old one is clean. Install a new cam and all new lifters. Probably install a new ATI balancer pulley. New heads from AHP with PSI 1515 springs this time.

This plan may have to change if I find much debris in the oil filter and bottom of the engine, but it is what I am thinking now. I will consult with others tomorrow.

03BlkZ

Why is it that there seems to be so many lifter/cam lobe issues with these cars? Is it from spinning up to 7k?

Che70velle