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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
So browsing the inter webs last night I came across the picture below. Seems that this guy had a set of AHP reworked heads that dropped a valve, I was hoping maybe someone on here knew more about it or maybe Kohle could shed some light on exactly what happened? "A few hundred miles" leads me to believe something was wrong from theget go somewhere.
1) Customer requested to reuse his spring pack (we highly recommended they be replaced).
2) Customer already had an aggressive racing camshaft in the vehicle.
3) In an email we were recently sent we were told:
"-Engine blew on a 2nd to 3rd gear shift when I clutched in on the front stretch"
Electing to reuse your old dual springs against the shops recommendation is not a good idea.
Especially if your old dual springs that you want to reuse have previously been on the car w/an aggressive cam and tracked/beaten on. In this instants the springs were several years old with lots of heavy run time/track time on them and unknown mileage (the springs were on the vehicle when the customer purchased the vehicle a few years back).
A new spring pack as per shops recommendations would have prevented a valve from floating into a piston on a 2-3 missed shift/over rev.
This is a result of not following shop recommendations (to replace the worn out dual springs) and customer driving style, not our workmanship or product.
1) Customer requested to reuse his spring pack (we highly recommended they be replaced).
2) Customer already had an aggressive racing camshaft in the vehicle.
3) In an email we were recently sent we were told:
"-Engine blew on a 2nd to 3rd gear shift when I clutched in on the front stretch"
Electing to reuse your old dual springs against the shops recommendation is not a good idea.
Especially if your old dual springs that you want to reuse have previously been on the car w/an aggressive cam and tracked/beaten on. In this instants the springs were several years old with lots of heavy run time/track time on them and unknown mileage (the springs were on the vehicle when the customer purchased the vehicle a few years back).
A new spring pack as per shops recommendations would have prevented a valve from floating into a piston on a 2-3 missed shift/over rev.
This is a result of not following shop recommendations (to replace the worn out dual springs) and customer driving style, not our workmanship or product.
Last edited by American Heritage; 03-18-2017 at 10:25 AM.
Reason: spelling
This is a good reason to check/replace springs on a strong cam'd engine periodically, even if the springs are the correct ones for the build. My parts supplier and builder both recommended 20K miles. That obviously should be sooner if the primary use of the car is track events.
Hey guys that's my head for sale. Nothing fishy about it. Valve dropped right after I had them done.
I Definitely never refused any spring pack!!! Took the car to AHP and told them I wanted it done correctly and accepted and paid for all their recommendations. If I was trying to cut corners I would have done the head replacement myself which I can easily do, but instead took the car to them so it was done 100% correct up to their standards.
1) Customer requested to reuse his spring pack (we highly recommended they be replaced).
2) Customer already had an aggressive racing camshaft in the vehicle.
3) In an email we were recently sent we were told:
"-Engine blew on a 2nd to 3rd gear shift when I clutched in on the front stretch"
Electing to reuse your old dual springs against the shops recommendation is not a good idea.
Especially if your old dual springs that you want to reuse have previously been on the car w/an aggressive cam and tracked/beaten on. In this instants the springs were several years old with lots of heavy run time/track time on them and unknown mileage (the springs were on the vehicle when the customer purchased the vehicle a few years back).
A new spring pack as per shops recommendations would have prevented a valve from floating into a piston on a 2-3 missed shift/over rev.
This is a result of not following shop recommendations (to replace the worn out dual springs) and customer driving style, not our workmanship or product.
gotcha kohle. Thanks for the prompt reply. So basically, a valve spring failed and that's what caused the valve to float and get smacked into the piston? In other words it was the "common" ls7 failure
What exhaust valve? GM / stock, aftermarket, date of manufacture, mileage, etc?
Also, "nothing" is bullet-proof. IMO, the stock cam is already agressive.. Then you are tracking the car on road courses with an even more aggressive cam?? People around here are too greedy - you know the factory GM race cars made less than 500HP, right?
I am sorry for the loss, but depending on the details, this sounds a lot more like a hardware component failure than anything AHP did or could do to control.
They don't make exhaust valves and they can't control what cam you put in your track day engine.
Last edited by Dan_the_C5_Man; 03-18-2017 at 11:37 AM.
It appears from the ad the heads only had 300 miles on them? To me right there that signifies it most likely isn't a result of the poor guide wear characteristics of a factory ls7 head. This appears to be a faulty hardware piece vs a failure caused by a worn guide and wobbling valve issue
It appears from the ad the heads only had 300 miles on them? To me right there that signifies it most likely isn't a result of the poor guide wear characteristics of a factory ls7 head. This appears to be a faulty hardware piece vs a failure caused by a worn guide and wobbling valve issue
There is no way you can make that determination based on the evidence at hand.
Floating a valve if so, is not mechanical failure, it is driver error.
There is no way you can make that determination based on the evidence at hand.
Floating a valve if so, is not mechanical failure, it is driver error.
Originally Posted by outhouse
That much was obvious
slow down there cowboy...... when I said faulty piece of hardware I meant as in a bad spring, bad valve from the factory, or something similar....even a valve spring that floats is faulty hardware because a dual spring shouldn't be floating at 6800rpm or so especially enough to where it causes ptv contact. Driver error is shifting 2-3-2 and forcing the engine to overrev which could cause this problem. I in no way was saying it was anyone fault though hers.
calm down there bud
Last edited by redbird555; 03-18-2017 at 11:53 AM.
I read kohles response and missed his which was below it. Kohle did not say anything about valve float. He just said it was a spring problem, which usually means, it failed lol jeez. And to add to that a spring floating to the point where it's smacking the valve into the piston is a failure. The part is not performing it's job as intended and needs replacement. It just may not be failure as in it breaking
Maybe you need to step step away from the internet and adjust the attitude a bit then come on back before you start making 4-5 posts jumping all over peolle
I have AHP heads this thread was made to shed some light on a situation.
Last edited by redbird555; 03-18-2017 at 11:58 AM.
I'm the typical car enthusiast just like many of you here. Drive the car occasionally on the street and then at HPDE/TT events in SoCal like SpeedVentures and NASA. I should be at most of the NASA track days this years and some of the SpeedVentures and you all are welcome to come out, talk about cars, and I'll give you a ride if you want.
As most of us have figured out by now these cars are not bulletproof and failures to the exhaust valves whether stock or aftermarket do fail. Mine failed and I put a new engine in it and it is now running again. Obviously I would have preferred to not buy a new engine but thats what happens with these cars.
It had the standard AHP package of the Ferrea Exhaust and OEM Intakes. The exhaust valve guide and exhaust valve broke. Car was making 550rwhp. Had a regular track/street type cam, callaway honker, ported stock TB, and stock intake manifold. So nothing crazy on it and probably similar to most other peoples build. It's a 2008 and has approx 20K miles (mostly street miles and more recently some track days).
I'm happy to answer some questions about my car but I'm not here to get into a mud slinging contest like I often see on here about what vendor makes the best heads. I don't have that info...all I know is they are all prone to failures. I'm just a regular consumer/enthusiast like most the rest of you on here.
Hey guys that's my head for sale. Nothing fishy about it. Valve dropped right after I had them done.
Can you please tell us brand/model of all the valve train components.
Cam
push rods
rocker arms and any modification to them
retainers
springs
intake valve
exhaust valve
Do you know if this combination of valve train parts has ever been spintron tested? Was it an intake or exhaust valve that dropped? Any pictures of the broken parts would be great. If you put a good valve in the guide where the dropped valve was, does it wiggle?
...and no it wasn't a mechanical over rev - car was accelerating in second gear at approx 6600 rpm when it blew. I then clutched in, put it in 3rd, and had no power obviously.
That's a good honest response, I myself would like to know the cause of failure. So in your mind if it wasn't the Springs then what was it? Pretty obvious it was a case of the guides wearing out
Great response from the owner. Can you provide the cam specs? Do you have an idea about the disconnect between AHP and your version on the reuse of parts?
And when you say "valve guide broke", I assume you mean a piece missing from the bottom, probably a result of the end of the valve snapping off and bouncing around in the cylinder head?
Last edited by Dan_the_C5_Man; 03-18-2017 at 12:07 PM.
03-18-2017, 07:51 AM
AHP head failure. Story sounds fishy?
