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C6 Corvette ZR1 & Z06General info about GM’s Corvette Supercar, LS9 Corvette Technical Info, Performance Upgrades, Suspension Setup for Street or Track
Or .. just to play devil's advocate.. maybe they know more than a handful of folk on a forum and it's not as prolific an issue as some think.
After all, how many Z06's were produced? > 100k? This forum knows of what, a few hundred that went boom? How many of those were abused I wonder... we'll never know because it's human nature to lie through your teeth.
Not to say it can't be an issue, just that in all likelihood it's not as prolific as most forum goers seem to believe. It all seems a little like going to an AA meeting and being shocked to find everyone is an alcoholic.
You're one of the very fortunate few to have a good test result...and I always love it one that one test result now becomes proof positive that the issue isn't as wide spread as one might think. I think I can count on one hand as to how many times I've seen this. It's your opinion, and your entitled to it...but it's just that, an opinion. Yours is in no more valid than mine, or anyone else's.
Are you the original owner? How do you know those are the OE heads? Just don't want to make any assumptions here. At the end of the day, I'm glad yours tested fine...I hope you checked all 16 valves, as I've seen cars with only two or three bad guides. Checking them is the awareness piece we all hope owners take notice of.
In my case, my '09 C6Z was discovered to have 14/16 guides out of spec, with the remaining two at the limit...all with only 15k street miles. Inspected by AHP, witnessed with my own two eyes, and validated by a GMPP field claims adjuster. Rebuild done under warranty by AHP, and I sleep good now.
By the way...production numbers are far less than 100K units....closer to 28k for the entire run of C6Z's. As for the AA analogy...that really doesn't apply here. The CF isn't comprised of members who came together in the hopes to find answers on LS7 failures, the CF and its members were around for a very long time prior to C6Z's blowing holes in blocks.
Oh...and what's your opinion on brand new replacement heads taken off the parts shelf, being inspected, and subsequently failing as I mentioned in my other post?
These conversations have gotten so tedious, it's impossible to describe just how much.....I'm no longer interested in educating those who want to believe differently. If they loose an engine, they can feel better by blaming it on the Russians.
Well said Michael...I'm all for getting the information into the hands/minds of new members. What they choose to do with it is entirely on them.
Moderators: It seems to me Kohle's significant efforts and well written write-ups/pictures on initial wiggle test procedures and subsequent heads off guide bore measuring ought to be made a sticky!
Last month I had Rich at Abel Chevrolet replace my heads with a set of AHP Pkg 4 rebuilt heads from Kohle. My 7,950 mile 2008 is out of warrantee (age) so I chose to replace the heads without "official" initial wiggle test results. My Z06 Limited Edition is completely stock and will remain so other than the replacement heads and it is not tracked.
Recently, Kohle followed up and provided actual guide bore measurements of my returned core heads. Basically, my heads weren't too bad. All exhaust valve guides were still in spec. The driver side head had one intake guide slightly out of spec and one very close to out of spec. The passenger side head had three intake guides significantly out of spec.
I suppose there are those who might argue I was premature in my choice to replace the heads. For me it was absolutely the wise choice for peace of mind and future resale value.
They pulled off very easily with a quick twist (I use this tool)
I lightly tapped the new ones on using a deep socket (to clear the stem) and a small rubber hammer, they all seated very easily.
Edit: By the way, considering how easily they came off, you could probably reuse them. I assumed I would mangle them all to hell like every other motor I've worked on, so bought the above just to be sure. Probably cheap enough to just replace anyway, might as well have new seals in there.
Or .. just to play devil's advocate.. maybe they know more than a handful of folk on a forum and it's not as prolific an issue as some think.
After all, how many Z06's were produced? > 100k? This forum knows of what, a few hundred that went boom? How many of those were abused I wonder... we'll never know because it's human nature to lie through your teeth.
Not to say it can't be an issue, just that in all likelihood it's not as prolific as most forum goers seem to believe. It all seems a little like going to an AA meeting and being shocked to find everyone is an alcoholic.
I suppose there are those who might argue I was premature in my choice to replace the heads. For me it was absolutely the wise choice for peace of mind and future resale value.
That would be extremely foolish on their part. Why take the risk, and postpone the inevitable? You absolutely did the right thing.
He did not even follow directions, used the wrong math, and did not check all his valves.
I honestly didn't scrutinize his step by step procedure. I just find it fascinating when one rare individual out of 28k units produced all of sudden can come to a conclusion that this issue, isn't really an issue. I wonder if their opinion on the matter changes if their outcome/results weren't favorable?
These conversations have gotten so tedious, it's impossible to describe just how much.....I'm no longer interested in educating those who want to believe differently. If they loose an engine, they can feel better by blaming it on the Russians.
I agree
I pretty much read them still but have little to add. Having lost a motor and seeing numerous failures and inspected heads out of spec there is no doubt in my mind. Either have the heads done or have a warranty.
What's the highest mileage AHP heads that have been wiggle or otherwise had the guides checked?
New LS7 heads off the shelf have bad guides, cars with under 10k have shown bad valves.
I'm sure it is factual Kohle has heads out there with over 10k and still have guides in spec. A few have reported in spec clearances.
To date not one complaint or out of spec guide has been reported, so while there is a lack of data to some extent. The lack of bad data is more telling because when you have a problem your on a forum screaming. Has not happened.
I believe Kohle has reported 30-40k on his heads so far.
Haha I was thinking the same thing. I was real close to busting out Minitab and getting all technical.
I spend all day in minitab. Don't need to open it up for fun. Finished all sorts of minitab certs end of last year. Probably have 6 weeks of official minitab training.
New LS7 heads off the shelf have bad guides, cars with under 10k have shown bad valves.
I'm sure it is factual Kohle has heads out there with over 10k and still have guides in spec. A few have reported in spec clearances.
To date not one complaint or out of spec guide has been reported, so while there is a lack of data to some extent. The lack of bad data is more telling because when you have a problem your on a forum screaming. Has not happened.
I believe Kohle has reported 30-40k on his heads so far.
From my experience a lack of bad data does not guarantee positive results. I'd like to hear from Kohle on any data/findings AHP has on the durability of their heads.
This is stock with 50k+ miles?? If so that's shocking. Maybe u got lucky. If its stock I wouldn't trust the rest. At least check one set on the other head.
Cyl 1
Intake - 0.0022
Exhaust - 0.0024
Cyl 3
Intake - 0.0018
Exhaust - 0.0025
MTPZ06,
Nowhere did I say this flat out isn't an issue, merely pointing out that GM did state that 2007 isn't affected and perhaps that's why this 2007 car isn't exhibiting the problem... Apparently GM don't know anything, per one reply! Guess we should all dumpster our cars since they were made by know nothing charlatans.
outhouse,
For your information I actually followed this write up which is substantially more comprehensive. My question re: continuing was genuine, yet you offer nothing but sarcasm in return. You seem awfully upset, did I offend you?
In any case, the heads are coming off later this year for an E85 conversion. I just wanted to see if it was a priority before heading out to the track again.
Not me personally, just the whole community here that opposes your opinion here in full.
We look out for each other here.
I actually followed
You followed nothing if you did not test all guides. Hib did not tell you to guess clearences.
You also admitted different math.
, the heads are coming off later this year
That's good, the results may surprise you, and you will see exactly why we only advise that people CHECK them, and if out of spec then replace/rebuild.
...just the whole community here that opposes your opinion here in full.
Look, I went back and read all of my posts in this thread to see which one triggered you. I believe it was the one where I suggest this might not be a 100% failure rate problem, and that GM probably have vastly more data than anyone on this forum. I genuinely don't understand your angst with this.
You seem a little unhinged.
Happy to make this my last post in the thread if that calms you down.
Happy to make this my last post in the thread if that calms you down.
I'm thick skinned I just tell it like it is, id rather not mince words here so I get to the point regardless of feelings. Please don't take it personal I don't.
Regardless of rhetoric bud, this is a real problem when brand new heads in 2014 have out of spec guides, long after GM admitted there was a problem.
We don't sell rebuild first ask questions later, we sell check first and if out of spec address the issue before failure. Simple as that.
Nowhere did I say this flat out isn't an issue, merely pointing out that GM did state that 2007 isn't affected and perhaps that's why this 2007 car isn't exhibiting the problem... Apparently GM don't know anything, per one reply! Guess we should all dumpster our cars since they were made by know nothing charlatans.
No, but you insinuated that this is blown out of proportion solely due to this forum...strictly because of your individual inspection results, yes? Would you have said the same thing if you had failed your inspection?
GM knows nothing, they have no real data as many of these failures occured out of factory warranty, and most rebuilds are done by independents. GM's supplier of LS7 heads (Linamar) is terrible when it comes to QC. They're responsible for the e-Diff failures in the C7's as well, by not properly filling them with fluid. What is GM good at? Covering their tracks, and burying important/actionable data...until people die.
From my experience a lack of bad data does not guarantee positive results. I'd like to hear from Kohle on any data/findings AHP has on the durability of their heads.
A year or so ago we pulled apart a set of our package 4 heads that had 60,000 miles on them and found that all the guides were still well within spec.
We recently pulled apart 2 sets of our package 4 heads with Moldstar90 guides that were used on heavy duty track vehicles. One set had a stock cam and the other set had a decent size aftermarket cam. Both sets were right where we originally set them up at, zero measurable wear on both sets.
01-15-2017, 02:08 PM
Well said Michael...I'm all for getting the information into the hands/minds of new members. What they choose to do with it is entirely on them.
