175rgr

Hello all,

I just stepped into the c6 z06 world about a week ago after selling my 800rwhp c5 z06. I purchased a car here off of the forums

http://forums.corvetteforum.com/c6-c...-for-sale.html

The car turned out great everything promised great car great seller.

Being a tad on the paranoid side about things and the LS7 head issues I decided to pop the valve cover off the passenger side and see if i could get one to wiggle even with the spring still on it. This is what I found, let me know if this is me being paranoid or it looks a little out of spec.

The heads were reworked with bronze guides and re used the factory titanium valves.

***********Update Below****************

Looks like it had about .09 - .10 movement in each direction with pretension on the dial indicator.

Also, I loosened all rockers and did an "eye" wiggle test to the rest of them, every single other valve has no noticeable wiggle with the exception of Cylinder 4 intake valve and Cylinder 8 intake valve. All other valves both exhaust and intake on all other cylinders had no noticeable movement.

************Updated Video w/ dial indicator************





Final course of action:

Purchased Stage 4 heads from American Heritage and he is accepting my current as a core so no downtime. Below you will find the full specs on the motor/cam and head setup for those valvetrain gurus or those with similar setups who are curious. If you would like any more information feel free to email me (dgpiper.06@gmail.com) or PM me.

Block: Factory GM LS7
CI:429.52
Bore: 4.1340
Stroke: 4.000
Crank: Compstar 4.000
Rods: Compstar 6.125
Pistons: Ross #132321 Forged +3.00cc dome
Cam: 235/248 .645 .660 115lsa
Heads: Stock LS7 milled .005
Chamber: 70cc
Rockers: GM LS7 W/Trunion upgrade
Compression: 12.11 : 1
Hand Ported
5 Angle valve job
Bronze Valve Guides

Only abuse motor has seen was tuning on the dyno and maybe a few spirited street pulls.

Made 603 rwhp and 565 rwtq with 18 degress of timing, 93 pump gas on a mustang dyno.

2,000 miles on the motor when I discovered the wigglers

phipp85

Video won't play for me.

021z

I would bet those are toast but take it apart and get a dial indicator on it. Who did the heads?

Undy

Don't know if I'd waste my time with a dial indicator. It sure appears that the heads need redoing with that visible amount of movement...

Intake valve too!

Michael_D

Just how much force are you applying? The Ti valve will bend, but that looks a bit too much. I'm also going to guess that lift on that cam is pretty high, and with OE rockers, you may in fact have wasted guides. I'd throw a dial on a couple valves.

propain

Awesome car. Welcome to the LS7. Yup, looks like those guides are toast but I would throw a dial on them.

I echo Michael.... OE 1.8 rockers, Bronze guides, big lift cam and those guides are toast.

phipp85

I was on my phone earlier so thats why I couldn't view it.

Yeah I would say its time to pull some heads off, especially if they all move that much with spring pressure still on them.

175rgr

Funny thing is, the motor has just about 2k miles on it since rebuild. Anyone make a good aftermarket or reworked LS7 heads that will accept these as a core or maybe anyone who would buy these. I just sold my second car and don't have a beater at the moment so I cant afford a lot of downtime. Would look to buy new and swap heads in a weekend and sell or send these in for a core.

LT1Pat

Fixing loose valve guides is almost like a rite of passage for new C6Z owners.

On a positive note: new owners quickly become familiar with their motors when they do a heads (and usually a cam) swap.

Michael_D

I had 5k on a fresh rebuild. Guide clearance was out of range of my bore gauge (.020) on two intakes. All intakes were toast. Exh were all out of spec too, but not as bad as the intake. All from rocker side load.

American Heritage

My bet is they are toast.

Recommend you go with a Hardened PM guide when you rebuild.

We accept Core Sets. In fact we have core sets loaded and ready to go.
http://www.americanheritageperformance.com/

Lots of CF member running our heads... even a few in this thread.

RamAir972003

So bronze guides are not the fix i presume...!!!! I am running pm guides in mine with ss valves.. 12k on.mine so far....

'06 Quicksilver Z06

Any tumble polish of the stock intake valves before they were used with the bronze guides?

Also, not all "bronze guides" are the same. There are different type bronze alloys used in various valve guides. Were these manganese bronze guides?

175rgr

Update:

I'm still not going to name names on shops etc... just because that's not the way I do business unless there is a major issue that would sway my opinion to believe that I should inform possible customers to stay away but....

I spoke with the shop who did the heads and has done many LS7 builds. When I spoke with them and shared the video to them they basically stated that its normal and there was very little probability the guides were wiped out so quickly. I then brought up the issue with using OEM rockers and he acknowledged that could be a problem but still said its highly unlikely the guides were out of it so quickly.

His recommendation was to monitor oil consumption and if it begins to consume oil then I could send them back to them and they would "help me out" on the pricing if they turned out to be bad. I voiced my concern to him about the car already running 12.11 : 1 static compression ratio on pump gas the way it is so any oil getting into the cylinder period could be dangerous for a motor already on the edge of safe compression and pump gas. He also voiced his concern with the 12.11 : 1 compression and informed me they highly advised the shop that was assembling the car that this was a bad idea etc, but that shop claimed its all in the tune we know what were doing etc etc etc...... The engine builder also mentioned that had a customer bring an LS7 car in and it looked exactly the same as my video so they pulled the heads and upon putting a dial caliper on them they weren't "That bad, or as bad as we thought".

Overall here is my opinion, I trust that the guys who built the motor knew what they were doing and voiced concern to the shop building the car to use aftermarket rockers and not to run 12.11 : 1 compression. My concern is that I don't feel like risking an $8,000+ dollar motor over something like a valve guide issue and from my standpoint I would sleep safer at night if I just replaced the heads/rockers ect... for not only piece of mind but also safety.

Let me know what you guys think, I don't want a pissing match over shops and blame and all that, I just want an honest opinion on their suggestion to monitor oil consumption as well as a set of heads/valvetrain that I can bolt on be free of all LS7 valvetrain issues.

Thanks for the all the replies and help thus far.


any opinions or experience on running different rockers with Ls7 heads? Harland sharp?

Drew

Michael_D

Drew - Just throw a friggin dial on a couple valves. I couldn't care less what "the shop" says, or their reputation, blah, blah, blah.. There is a saying I like a lot, and pretty live by - Trust, but verify. I have a thread you can look at discussing high lift cams and rockers. I'm too lazy to find it right now.

ILS07

They'll all say their rep is second to none. I've never seen a shop say "We do pretty mediocre work and occasionally we get lucky and produce an awesome setup."

Regardless of reputation or prior success, if you feel uneasy or concerned about something, bring it up. They are working for you. If they feel they don't need your business or are otherwise too busy to discuss things with you, go somewhere else.

-EDIT-

Regarding your question about other rockers, I went with CHE but my car has a build date right in the middle of the great '07 rocker debacle (car at 12,3xx miles right now). You may be aware, but they are just modified stock rockers (different trunion design). They definitely feel smoother to me when checking the range of motion in my hand. You'll have people argue for and against CHE and HS rockers, so do a lot of research and ask questions before you make a decision that you feel good about.

phipp85

If you don't have a dial indicator I would at least pop that valve spring off and wiggle it with no spring pressure so you can really get a feel for how loose it is.

LT1Pat

It's a bit of a gamble, but if you lose it's a 10k bill. If I had to guess, that movement appeared to be ~.010.

Also, I wouldn't even acknowledge anything that shop said. You're on a forum with engine builders, engineers, users, mechanics, etc. with hundreds of data points and experiences and the last place I would seek input is from a shop that's done a few LS7's before.

Unreal

12:1 compression could be fine if the tune is conservative. Just means you are going to run less timing than 11.5:1 or what most people run. That wouldn't concern me.

I don't see anything wrong with stock rockers. I think the only real upgraded rockers are ones like Jessel, T&D, Crower, etc that are all $1500-2500 options and need the heads machined.

Les

My exhaust guides were way out of spec and my engine has never used any oil. That's not a trustworthy way of assessing valve guide wear or condition.