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243 Cylinder head question

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Old Dec 19, 2010 | 08:37 PM
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Default 243 Cylinder head question

I have someone who wants to sell me some cylinder heads. They have the 243 casting number, but on the inside of the head, it is stamped 5.7. I am not sure if these are heads for an LS6 or for an LS2 motor. I also have a part number of 12564825. Can anyone help? Does anyone know the differences?

Last edited by Bludog; Dec 19, 2010 at 08:37 PM. Reason: mispell
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Old Dec 19, 2010 | 08:42 PM
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Those are stock LS2 heads.
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Old Dec 19, 2010 | 08:46 PM
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Originally Posted by Bludog
I have someone who wants to sell me some cylinder heads. They have the 243 casting number, but on the inside of the head, it is stamped 5.7. I am not sure if these are heads for an LS6 or for an LS2 motor. I also have a part number of 12564825. Can anyone help? Does anyone know the differences?
I believe that is the part# for the C5 Z06's LS6 cylinder head (hence the '5.7' designation) but the LS6 and LS2 heads were virtually identical anyway (a difference in some of the valves).
The heads he's selling might've started life as bare castings bought in the aftermarket (not necessarily off of a car originally) as well.
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Last edited by LS1LT1; Dec 19, 2010 at 08:55 PM.
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Old Dec 19, 2010 | 11:33 PM
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Pretty sure the LS6 has the lighter hollow sodium valves. The head castings 243 are the same.
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Old Dec 20, 2010 | 04:34 PM
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Some of the early 243 castings that were on the C5 Z06 had the sodium filled valves. The majority had standard valves. How much does the guy want for them and does he know how many miles are on them? I can tell you if it is a good deal or not.

Jon
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Old Dec 20, 2010 | 06:15 PM
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Jon I thought that most of the 02-04 C5Z had the sodium filled valves.

01 had the blue valve springs and had the standard valves
02-04 had the yellow springs and the light weight valves
05 and up had the silver springs and standard valves

All the above had 3.899 bore size, yes even the 4 inch bore engines

I can be corrected if needed!

Randy
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Old Dec 21, 2010 | 12:03 AM
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Thanks to everyone for the help. PM sen to Jon @ Texas
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Old Dec 21, 2010 | 04:04 PM
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PM sent.

Yeah that's right, Randy. I don't know why I put early. I guess since they are getting older now. If they had the yellow springs they are sodium.

Jon
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Old Dec 21, 2010 | 05:24 PM
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Originally Posted by Jon@Texas-Speed
PM sent.

Yeah that's right, Randy. I don't know why I put early. I guess since they are getting older now. If they had the yellow springs they are sodium.

Jon
Nice! I'm trying to keep up on that stuff, so when I'm 65 and my neighbor kids come back from the junk yard. I can tell them all about the 243 heads, years and etc. Like the old timers of today.

Randy
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