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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
Remember, depending on what rockers you use and which Ti ex valves (e.g., Ferrea), you may need to use lash caps on the exhaust valves.
From what I understand he is ordering Ti/Mo valves with hardened ends that do not require a lash cap. Delivery time on the valves is 2.5 to 3 weeks. One good thing it is a local delivery which will reduce shipping times. 3 weeks probably means I miss taking the car to my first track event and I will just attend as an instructor. At least that will save me the $150 Instructor only day charge.
He will do the bronze guides as soon as the new heads are here and be ready to assemble everything when the valves show up. If they get there in the 2.5 week time frame I will have just enough time to change the brake rotors, put in track pads, bleed the brakes and get the wheel alignment done before I put the car on the trailer.
He has offered to let me put the race seats in the car while it is sitting in the shop if I want to do that.
Here is my story as of tonight. First off I've owned my Z now for... Almost a month. I love every sec I have behind the wheel. She has 47k miles and the motor has never had a wrench on her until tonight. That being said she has been babied all 47k of those miles. I'm aware of all these valve issues even prior to buying the car. Honestly I don't care. My plan from day one even before signing the papers at the bank was to replace the heads. So within the first days of owning her I order a set of BR7's from Brodix. Now a month later and Brodix taking a long a$s time I decided to do my own "wiggle test" for peace of mine to my noticeably louder tick to the motor. So I ventured out to the garage with my gimped hand (story behind that) to see this for myself. I pulled both valve covers and rockers.
Peace of mind knowing I didn't fall victim to the needle bearing issue or a damaged valve. After removing each rocker one at a time I used my calibrated Frankenstein hand to check for movement. Note I have 9 stiches in my hand so I wasn't using my Hercules power for check for movement.
Out of all 16 valves I found most moved a little. The deal breaker was on 2 of the intake valves #3 and #4 had lots of play. #1 #2 #5 #8 very little play and #7 and #6 had no play. I may self proclaim myself as a genus but cant give you a dial gauge number from my fingers. The 9 stiches could have cause the miss calibration in numbers so I figured I wouldn't lie. Morel of the story is loose is loose and tight is tight. There was a difference between each valve which is enough for me to "ground" the vette till the new heads show up. Im a week out from getting the Brodix so I wont break my heart watching her sleep till then. Minus the minor damage discovered to the top of one of the valve caps she was good on the inside.
This gives me that warm and fuzzy knowing I wont have to open up the lower end looking for missing parts or bearings. Ill post the progress on the Brodix heads when they show up. Cheers.
P.S. Incase you wondered the 9 stiches came from one of my other projects I'm doing. Building 2 LT1 300hp corvette motors for my boat. Yes Corvette motors as in 100% to spec. Short of cast numbers they will be legit in every way. Only thing missing is a transmission and car attached to them. Ill post that project once there done.
If bad guides were causing the problem it seems like there would be substantially more engine failures due to dropped intake valves.
Bill
Shear, tensile, flexural, compressive, any and all stress on an object is directly impacted by the cross sectional area of the material involved and the force applied.
For an equal force, greater area will mean less stress on the object.
stress = force/area
Hollow - less material cross-sectional area, solid - more material cross-sectional area.
This doesn't even consider the the difference in loading dynamics on the exhaust valve compared to an intake valve based simply on when/how it opens during the combustion cycle.
EDIT: That's why I'm not particularly surprised intake valves would tend to survive longer than the exhausts.
Right, and it seems possible that in an "in-spec" setup (proper guide clearances, decent rocker wipe, tune not leaned out, proper valve seat location, no significant deviations in the exhaust valve wall thickness) the OEM exhaust valves are okay...but often it seems like one or more of those items are out of spec to varying degrees.
Though I am interested on hearing Michael D's theory on the head cooling design.
UPDATE: Valve Guide Clearances (These were all determined using a valve guide bore gauge and valve stem measurements)
UPDATE: I added the Valve Stem Measurements and GM Specs to the Chart.
Bill
So after finding two intakes out of spec by 0.0002 on the same head, GMPP paid for two new head assemblies and R&R labor? And let you keep the old head assemblies?
Here is my story as of tonight. First off I've owned my Z now for... Almost a month. I love every sec I have behind the wheel. She has 47k miles and the motor has never had a wrench on her until tonight. That being said she has been babied all 47k of those miles. I'm aware of all these valve issues even prior to buying the car. Honestly I don't care. My plan from day one even before signing the papers at the bank was to replace the heads. So within the first days of owning her I order a set of BR7's from Brodix. Now a month later and Brodix taking a long a$s time I decided to do my own "wiggle test" for peace of mine to my noticeably louder tick to the motor. So I ventured out to the garage with my gimped hand (story behind that) to see this for myself. I pulled both valve covers and rockers.
Peace of mind knowing I didn't fall victim to the needle bearing issue or a damaged valve. After removing each rocker one at a time I used my calibrated Frankenstein hand to check for movement. Note I have 9 stiches in my hand so I wasn't using my Hercules power for check for movement.
Out of all 16 valves I found most moved a little. The deal breaker was on 2 of the intake valves #3 and #4 had lots of play. #1 #2 #5 #8 very little play and #7 and #6 had no play. I may self proclaim myself as a genus but cant give you a dial gauge number from my fingers. The 9 stiches could have cause the miss calibration in numbers so I figured I wouldn't lie. Morel of the story is loose is loose and tight is tight. There was a difference between each valve which is enough for me to "ground" the vette till the new heads show up. Im a week out from getting the Brodix so I wont break my heart watching her sleep till then. Minus the minor damage discovered to the top of one of the valve caps she was good on the inside.
""BS" WIGGLE TEST SAVES ANOTHER LS7.." is the headline for today!
Congrats!
Last edited by Dan_the_C5_Man; 04-29-2015 at 03:20 PM.
So after finding two intakes out of spec by 0.0002 on the same head, GMPP paid for two new head assemblies and R&R labor? And let you keep the old head assemblies?
Is that correct or did I miss part of the story?
I think they just gave him new cylinder heads and did not cover the labor... My heads are being pulled as we speak with 47k miles. We shall see if GMPP will give me any help...
So after finding two intakes out of spec by 0.0002 on the same head, GMPP paid for two new head assemblies and R&R labor? And let you keep the old head assemblies?
Is that correct or did I miss part of the story?
Yes, that is correct. I don't know why they did what they did but they did it. As far as GMPP taking the heads I am not sure what they would have done with them. They are an insurance company that is part of Ally Bank not a manufacturer.
Yes, that is correct. I don't know why they did what they did but they did it. As far as GMPP taking the heads I am not sure what they would have done with them. They are an insurance company that is part of Ally Bank not a manufacturer.
Bill
Glad it worked out for you. Looks like excellent coverage w/ GMPP. That's good to hear
03-26-2015, 11:37 PM
