[Z06] Broken valve spring, Engine probably gone
Burning Brakes
Joined: Jun 2004
Posts: 1,083
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From: I'm not quite middle aged and I only own one gold chain! San Jose CA
I know you love that minivan Chuck, but you must drive the Z06 occasionally just for appearances sake! Your wife will let you drive the Z every once in a while I'm sure! I can even help with some lessons on shifting, etc! 
Pro
Joined: Mar 2005
Posts: 513
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From: PA
Originally Posted by Chuck Harmon
zo6vetteman2003,
Your suggestions are right on the mark regarding the 402 and such.
I ordered a LS2 402 with all forged parts. I will be using an aluminum flywheel with LS7 clutch and pressure plate. The cam my local Vette Shop recommended is a comp cam 228/230 with .591" lifts on 114 separation. I would like to keep the car discreet looking so I will continue to use the LS6 intake and throttle body. I have heard the the fast intake w/ 90mm is rather finicky and really only makes about 10hp more and only at the very top. It was suggested that I smooth my intake and match the ports - this is supposed to give me at least 5-8hp. I can probably live with the difference.
I had planned on waiting until later to do the heads and headers when $$ were a bit more plentiful, BUT..... I just ordered a set of long tube headers with high flow cats. Regarding the heads, I have a set of AFR 225's on their way so I am now in way over my head! It may not be the 427 I really lusted for, but I think that I will be over 400rwhp. Ideally, if I end up making as much as my much lamented '69 L88 clone did with a factory spec motor (486rwhp) I would be very satisfied. I loved the incredible power of the 69, but I also love the civility of the ZO6. Now I may actually be close to having both in one car.
I think I am about 3 weeks away from having it back in my garage. by then I'll have to have the keys to my wife's mini van torn from my hand.
Chuck
Your suggestions are right on the mark regarding the 402 and such.
I ordered a LS2 402 with all forged parts. I will be using an aluminum flywheel with LS7 clutch and pressure plate. The cam my local Vette Shop recommended is a comp cam 228/230 with .591" lifts on 114 separation. I would like to keep the car discreet looking so I will continue to use the LS6 intake and throttle body. I have heard the the fast intake w/ 90mm is rather finicky and really only makes about 10hp more and only at the very top. It was suggested that I smooth my intake and match the ports - this is supposed to give me at least 5-8hp. I can probably live with the difference.
I had planned on waiting until later to do the heads and headers when $$ were a bit more plentiful, BUT..... I just ordered a set of long tube headers with high flow cats. Regarding the heads, I have a set of AFR 225's on their way so I am now in way over my head! It may not be the 427 I really lusted for, but I think that I will be over 400rwhp. Ideally, if I end up making as much as my much lamented '69 L88 clone did with a factory spec motor (486rwhp) I would be very satisfied. I loved the incredible power of the 69, but I also love the civility of the ZO6. Now I may actually be close to having both in one car.
I think I am about 3 weeks away from having it back in my garage. by then I'll have to have the keys to my wife's mini van torn from my hand.
Chuck
I have been following your story..
First off, sorry to hear about your valve spring..
But also congratulations on the 402!
Where did you order it from?
Safety Car
Joined: Oct 2001
Posts: 3,504
Likes: 25
From: Insert Wittty Comment here
Chuck, sorry to hear about your troubles. I wish you all the best with the new motor project. I hope it brings you tons of smiles once its in.
I think with a bigger inch motor you'll see more gain with a FAST than say a 346. If you want stealth, consider having the FAST90 painted black to look stock.... and use the GM 90MM TB. A casual glance won't tip anyone off.
The cam is fairly small for a 402, so it should idle pretty close to stock. For a AFR headed combo I'd look more towards a 4 degree split Intake to exhaust, and narrow up the lobe sep, but thats just me...
I think with a bigger inch motor you'll see more gain with a FAST than say a 346. If you want stealth, consider having the FAST90 painted black to look stock.... and use the GM 90MM TB. A casual glance won't tip anyone off.
The cam is fairly small for a 402, so it should idle pretty close to stock. For a AFR headed combo I'd look more towards a 4 degree split Intake to exhaust, and narrow up the lobe sep, but thats just me...
Burning Brakes
Joined: Aug 2002
Posts: 1,083
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Originally Posted by DonWarren
I lost a Spring in my 03 with 14K miles same as you guys...No mods
Sorry to hear about your broken spring, but that new engine sounds like a killer
As far as the factory ls6 springs go, i've done alot of research on this subject due to the fact that i've lost 2 springs on 2 different occasions.
Like your wife both my breakages occured at zero load, first time was leaving a light and just releasing the clutch (6k on engine, not raced or no misshifts), the second I was at a light and had the clutch fully engaged(10 k on engine)
First breakage, they replaced the spring with a replacement ls6 spring, second breakage they replaced all springs with LS2 springs (because the original ls6 springs were discontinued)
Sorry for the long post, but hopefully this may help others.
If you get a bad miss in your engine (very lopy almost violent shuddering) shut off the engine immediately and Do not restart it for anyone. One fella E-mailed me and told me he dropped a valve and blew his engine when the tow truck driver asked him to restart it
I feel abit more confident with the ls2 springs, as I have not yet heard of an incident of a blown motor in an ls2 due to spring breakage.
For the record, there has already been a few incidents of broken springs and blown motors with the new c6 z06
Last edited by 03QuicksilverZ06; Jan 20, 2006 at 08:23 PM.
Thread Starter
Melting Slicks
Joined: Apr 2000
Posts: 3,286
Likes: 8
From: San Jose California
Wow! 
Twice, and you didn't lose the motor! You must be congratulated for supreme presence of mind to have shut it off so fast and avoided ruining the motor. Very good of you to post. I had been down a bit on power according to my G tech a couple months ago. I wonder if the valve spring was weak enough to be floating and the reason for my losing about 20hp before it broke?
Chuck
Twice, and you didn't lose the motor! You must be congratulated for supreme presence of mind to have shut it off so fast and avoided ruining the motor. Very good of you to post. I had been down a bit on power according to my G tech a couple months ago. I wonder if the valve spring was weak enough to be floating and the reason for my losing about 20hp before it broke?
Chuck
Last edited by Chuck Harmon; Jan 22, 2006 at 11:40 PM.
