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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
Like the title says, I just purchased an '08 Z06 2LZ with 25k miles.
The heads are not original, they are from the GM Performance catalog: the casting # is 12578449 on one end of the head and this other number at the opposite end reads = H3491093
Is the H3491093 a build date? Not sure what this number is...?
We did a check with GM on factory warranty repairs and these heads were not put on by a GM dealer as it doesn't show up anywhere on the warranty repairs.
Wish I knew more about the heads - no weird sounds, car is stock besides a Calloway CAI.
As mentioned by Outhouse, its best to at the very least do a wiggle test on an LS7 (c6z06) that you just purchased. If your handy with tools or just want to see how its done we have a write up for the wiggle test: https://www.corvetteforum.com/forums...-test-diy.html
We rework 2+ sets of LS7 heads per week and have done so for 4 years now.
Still need to do a wiggle test at minimum. Stock GM head of any kind "can be" trouble.
On cars like this it is important to know what you have, over guessing.
Congrats on the purchase OP! Assume nothing...at a minimum, the heads need to be checked for excessive guide wear using the wiggle method. Given that the car has a Callaway Honker intake, its most likely been tuned as well. Those intakes can cause surging from MAF turbulence; so much so, that Callaway designed a "diffuser plate" to install on cars with stock tune...but if you've seen that plate, you'd say why bother at all with the intake.
Congrats on the purchase OP! Assume nothing...at a minimum, the heads need to be checked for excessive guide wear using the wiggle method. Given that the car has a Callaway Honker intake, its most likely been tuned as well. Those intakes can cause surging from MAF turbulence; so much so, that Callaway designed a "diffuser plate" to install on cars with stock tune...but if you've seen that plate, you'd say why bother at all with the intake.
Thanks for the reply back. I'll get the wiggle test done first, probably by Matt at 21st.
The honker on this Z is one of the early models as it has "wing tabs" on each side of the plastic tunnel. No diffuser, either. Don't know if the car has been tuned, but it is super smooth around town, no surging that I can feel behind the wheel. Maybe that means it has a tune! I'm wondering, b/c these heads are GM, but not OE, if the previous owner had the "sense" to replace the heads from a reputable shop, then surely they went a bit further and updated the internal parts of the head as well. I'll know next month.
I'm still in the honeymoon stage, car is 2 weeks new to me. Learning about it from everyone's here.
Congrats on your purchase. You may want to just pull the spark plugs as well and monitor your oil level to see if you are using oil. You do know to wait about 10-15 mi it's after turning engine off to check the oil? Good Luck and Have Fun
Congrats on your purchase. You may want to just pull the spark plugs as well and monitor your oil level to see if you are using oil. You do know to wait about 10-15 mi it's after turning engine off to check the oil? Good Luck and Have Fun
^ first get the engine oil up to operating temp (160*F--175*F oil temp), make sure car is level, and check oil 10-15 mins. after shutting-off the engine.
OM indicates 175* oil and 5-20 minutes after shutdown to check level. I do it ~5+ minutes. It is more important to do it consistently for both temperature and time waited. The difference between 175* oil and 250* oil is a full mark(hole) up the stick.
What does 175*, 250* mean? and who or what is OM? Reason I'm asking is I'm looking at a 2007 Z06 , 24,000mi . and know nothing about vettes, Euro guy until now.
Missed post 10 thanks. Does a normally driven (not bouncing off the rev limiter all the time) vette likely to have valve guide issues? Trying to figure out if all LS7 have this problem or just those driven hard ( as they should be)? I'm about to pull the trigger on a car but the offer will depend on if I might have to do heads or not. Sucks to be a rooky.
Missed post 10 thanks. Does a normally driven (not bouncing off the rev limiter all the time) vette likely to have valve guide issues? Trying to figure out if all LS7 have this problem or just those driven hard ( as they should be)? I'm about to pull the trigger on a car but the offer will depend on if I might have to do heads or not. Sucks to be a rooky.
Stu
OM is Owners Manual. If you don't have one you can go to chevy.com and download a copy for your year Corvette.
Z06's have had bad guides as early as 2-3,000 miles and were essentially garage queens not driver for their performance. All years are subject to the guide wear. Performance events may accelerate the wear (not certain), but by no means are they a requirement to have trouble.
As has been indicated, unless the seller documents the work fully, at least have the wiggle test done by a competent shop. Given some of the results we have seen on the forum, if it passes the wiggle test the guides are good. If it fails they may be bad, but might not be bad. The heads would have to come off to verify good/bad and if they are already off the guides may as well be replaced by a competent shop.
Speculation, but one of the reasons Chey disavowed the wiggle test is they replaced some heads under warranty and then found the heads replaced had guide wear within spec. Regardless, Chevy has not been above board on this issue. Did they honor most warranties, yes. Have they disclosed all they years with problems, no, or let customers with 6 year old cars with 4-10K miles out, yes.
I wanted to have my heads checked before they went off warranty at 46K miles, all but 2 intake guides were out of spec.
Gentlemen - Here are the pics of my heads, which are from the GM Performance catalog. I know that these were not installed by warranty, we checked. The previous owner paid a shop or a dealer for install.
Last edited by 1971 Judge; 10-27-2016 at 03:35 PM.
OM indicates 175* oil and 5-20 minutes after shutdown to check level. I do it ~5+ minutes. It is more important to do it consistently for both temperature and time waited. The difference between 175* oil and 250* oil is a full mark(hole) up the stick.
The owners manual does not specifically say to check the oil when the oil temp is 175 degrees. it says...". To obtain an accurate engine oil level reading, warm up the engine to at least 175°F (80°C). Cold oil will not give a correct oil level reading."
It says to warm up the "engine" to at least 175 degrees. I think most people regard the coolant temp as representing the "engine" temp, not the oil temp.
Anyway, if I had to wait until my oil reached 175 degree before I could check the oil level, I could only check the oil level on a hot August afternoon after doing several WOT runs. Most of the time, even after driving for hours with ambient temps below 80, my oil temp never exceeds 160 degrees. Ambient under 60 and I'm lucky to see the oil reach 140 degrees with normal driving.
Driving all day at 90 MPH across Kansas with ambient at 105 degrees, my oil was up to 185.
The owners manual does not specifically say to check the oil when the oil temp is 175 degrees. it says...". To obtain an accurate engine oil level reading, warm up the engine to at least 175°F (80°C). Cold oil will not give a correct oil level reading."
It says to warm up the "engine" to at least 175 degrees. I think most people regard the coolant temp as representing the "engine" temp, not the oil temp.
Anyway, if I had to wait until my oil reached 175 degree before I could check the oil level, I could only check the oil level on a hot August afternoon after doing several WOT runs. Most of the time, even after driving for hours with ambient temps below 80, my oil temp never exceeds 160 degrees. Ambient under 60 and I'm lucky to see the oil reach 140 degrees with normal driving.
Driving all day at 90 MPH across Kansas with ambient at 105 degrees, my oil was up to 185.
No question this is an issue so I always checked it after doing some local stop and go traffic where the oil would get to 175*. I know if I used the water temp, when water got to 175* the oil temp could still be barely over 100*, which I would consider "cold oil". I know going from 175* oil to 250* oil makes the oil level change from middle hole to top hole, so 100* oil probably drops the level by nearly that amount. Overfill by a 1/2 quart on either the 8 or 8 1/2 quart system shouldn't cause any big problems but may push more oil into the intake manifold.
Everyone has to filter through the advice they get here and choose what they prefer to do.
10-23-2016, 02:56 PM
Just purchased 2008 Z06
Congrats on the purchase OP! Assume nothing...at a minimum, the heads need to be checked for excessive guide wear using the wiggle method. Given that the car has a Callaway Honker intake, its most likely been tuned as well. Those intakes can cause surging from MAF turbulence; so much so, that Callaway designed a "diffuser plate" to install on cars with stock tune...but if you've seen that plate, you'd say why bother at all with the intake.
