Road trip cut short

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Mar 29, 2008 | 12:40 PM

#21

Numb

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From: Austin Texas

Quote:

Originally Posted by Veni, Vidi, Vert

Sorry to hear that. Just out of curosity, was the spring broke near the top or in the middle??

In the middle if I remember correctly. I'll take some pictures as I take it apart today.

Mar 29, 2008 | 12:53 PM

#22

JCSZ51

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From: Freeburg IL

Cruise-In IX Veteran

Hopefully it's just a valve and you'll be back on the road quick. I'm only an hour or so away, let me know if you need a hand.

good luck !!

Mar 29, 2008 | 04:02 PM

#23

ALLEGRO

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Joined: Feb 2003

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From: Memphis Tennessee

Though I am really sorry to hear of your problems, there is a "silver lining" to this all. It sounds like you now have great excuse for an LS7 or hotter mill.

At least revel in "what might be."

Mar 29, 2008 | 04:24 PM

#24

ajg1915

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Joined: May 2005

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From: West Norriton PA

St. Jude Donor '08

Hopefully it's just the the valve or head that is damaged and you can pick up a used set of heads cheap.

Mar 29, 2008 | 08:16 PM

#25

Numb

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From: Austin Texas

Man, I can't belive it, but it looks like other than the valve spring, nothing else broke! The valve spring snapped right in the middle, but there isn't a scratch on either the valve or the piston... nice, normal looking carbon coating. How is that even possible?? I have some nice pics of everything, but I don't have my camera cable with me.... I'll have to post them later.

Soooooo, it's already taken apart, and LG Motorsports is right down the road - I pretty much HAVE to put it back together with one of their G5X3 cam/spring kits.

Mar 29, 2008 | 08:23 PM

#26

ajg1915

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From: West Norriton PA

St. Jude Donor '08

Quote:

Originally Posted by Numb

I would still have the head checked to make sure that the valve or valve seat did not get damaged (that you can visually see). I guess the valve never dropped all the way down but just didn't have enough pressure to close the valve causing the mis-fire.

Good luck getting it fixed up.

Mar 31, 2008 | 12:14 PM

#27

Boob

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From: Austin TX

Quote:

Originally Posted by ajg1915

Get it to a machine shop and have the valve guide checked to see if it's within spec all is good. Glad to hear it didn't cost you a shortblock.

Mar 31, 2008 | 01:00 PM

#28

LDB C5

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Joined: Sep 2006

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From: Stillman Valley Illinois

I feel a pair of Trick Flow's in your future.................

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Mar 31, 2008 | 07:31 PM

#29

Numb

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From: Austin Texas

Well, if you're going to take your car apart, you might as well put it back together a little better. I drove down the road to LG Motorsports today, and they just so happen to have everything you could possibly want in stock... you really don't stand a chance. I drove off with:

LG Pro long tube headers
G5X3 v2 cam
Comp valvetrain kit (921 springs, ti retainers, pushrods, seats, etc)
ASP underdrive pulley
Vararam B2
ARP head bolts

I also picked up some .040 Cometic head gaskets, and at LG's recommendation, I'm going to mill the head down to 59cc and flycut the pistons.

Looking forward to getting it back together to see how much of a wakeup the Z06 is in for.

Mar 31, 2008 | 08:47 PM

#30

motogib1

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From: New Smyrna Beach Florida

Just out of curiosity, is that an 02 Z06? Didn't say in your profile. I understand the may have had a bad batch of valve springs produced in 02. There have been a few reported here on CF.

Mar 31, 2008 | 11:30 PM

#31

spicytuna

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Joined: Nov 2004

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From: Canadian Rockies

Quote:

Originally Posted by Numb

Well, if you're going to take your car apart, you might as well put it back together a little better.

Very nice!!!

I'm glad that your horror story ended with a happy ending. Let us know how it rides after you get it back.

Apr 1, 2008 | 12:59 AM

#32

Numb

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From: Austin Texas

Quote:

Originally Posted by motogib1

Just out of curiosity, is that an 02 Z06? Didn't say in your profile. I understand the may have had a bad batch of valve springs produced in 02. There have been a few reported here on CF.

Yep, it is an 02 Z06. Didn't know it was a trend for that year, but LG said they have piles of broken stock C5Z06 valve springs.

I finished flycutting the pistons tonight... a little scary at first gouging up the pistons in your perfectly good shortblock, but they turned out fine. Heads go to the machine shop tomorrow to get milled.

Apr 1, 2008 | 09:45 AM

#33

jovette

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From: Des Moines Iowa

How do you flycut the pistons and ensure that the weight / balance is the same for all 8?

Apr 1, 2008 | 08:43 PM

#34

Numb

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From: Austin Texas

Quote:

Originally Posted by jovette

How do you flycut the pistons and ensure that the weight / balance is the same for all 8?

Not 100% sure, but you're cutting each piston at TDC with the same tool, from the same angle, and to the same depth (.080). I measured the resulting cuts with a caliper, and they are all identical in size and shape. "Close enough" is the phrase that comes to mind.

Here's another question... At LG's recommendation, I had the head milled to 59cc and am going to use a .040 Cometic gasket. To reduce the chambers to 59cc, .036 had to be removed from the surface of the head... fairly significant numbers. But with all that change, they sold me stock length Comp 7.400 pushrods... wouldn't I need a shorter pushrod to offset the extra preload that milling the head and going to a thinner gasket will create? Doesn't make sense to me.

Apr 3, 2008 | 03:10 PM

#35

Billdog350

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From: East Hampton CT

Quote:

Originally Posted by Numb

I could understand a spring failure at high rpm on a missed shift, but I was just cruising along in 6th gear at 70mph. WTF?!

Granted I had aftermarket gold dual springs and a G5X1 equivalent "generic" cam..but I had the exact same thing happen to me!

I started planning on tearing down the motor and everything else, but common sense took hold. I put a spark plug adapter in that cylinder and checked if the cylinder would hold pressure when I put compressed air on it. If your piston has a hole, the valve seat is broken, or the valve is bent , you'll hear air rushing out either into your intake, bottom end, or exhaust.

I lucked out, my valve (new stainless valves from PRC), and piston were fine. I just installed a fresh valve guide seal (the old one was destroyed) and a new spring and I was good to go. I also checked the hardened pushrod for any micro cracks or bending...it was fine also. I've put another 5k mi on the car since the spring replacement with no issues. If you need a new valve guide seal, PM me, I can mail it to you so you don't need to buy a whole new set of 8 form gmparts house like I did.