C4 Tech/Performance L98 Corvette and LT1 Corvette Technical Info, Internal Engine, External Engine

Early '86 head CC question

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Old May 20, 2005 | 06:14 PM
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Default Early '86 head CC question

Are the cast iron L98 heads 58 or 64 CC chambers?
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Old May 20, 2005 | 07:23 PM
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Anyone?

Buehler?
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Old May 20, 2005 | 07:39 PM
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The aluminums were 58, so they must be 64 (or was it 72?)
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Old May 20, 2005 | 08:07 PM
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If they are iron, they were 72-74cc chambers.
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Old May 20, 2005 | 10:30 PM
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They are 76cc combustion chambers.
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Old May 21, 2005 | 03:41 AM
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Originally Posted by vader86
They are 76cc combustion chambers.
So they dropped 18cc's when it went to aluminum?!?! That seems a little hard to believe. I'm not saying that it's not right, just hard to believe.
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Old May 21, 2005 | 04:00 AM
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Do you know the casting numbers?

Last edited by Morley; May 21, 2005 at 04:06 AM.
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Old May 21, 2005 | 12:47 PM
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Originally Posted by Morley
Do you know the casting numbers?
No, I don't. Too much crap in the way to see the #'s. The old pistons had a slight dish. Even with the current flat-tops, a 76cc chamber would still have compression just under 9 to 1.
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Old May 21, 2005 | 12:49 PM
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The book Cor-Vette Specs lists 4.6 cubic inches. How many cc's is that?
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Old May 21, 2005 | 12:56 PM
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They are 76cc heads, and I believe the '128s were only a little smaller than that, then the '113s dropped to 58cc.

If memory serves the last 3 digits of our casting is '624.

Run a search, it will come up if you look.
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Old May 21, 2005 | 02:28 PM
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Originally Posted by vader86
They are 76cc heads, and I believe the '128s were only a little smaller than that, then the '113s dropped to 58cc.

If memory serves the last 3 digits of our casting is '624.

Run a search, it will come up if you look.

426624 was mine. POS with 76cc chambers. All over the web people say between 72-76cc on the '85 L98 TPI, which was because they were 'Smog Heads'..
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Old May 21, 2005 | 02:44 PM
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what would be the best replacement head to bump compression and still use 87 octane?
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Old May 21, 2005 | 02:46 PM
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Originally Posted by cmashark
what would be the best replacement head to bump compression and still use 87 octane?
Why would you even consider runing 87 octane??
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Old May 21, 2005 | 04:07 PM
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Originally Posted by MrNuke
426624 was mine. POS with 76cc chambers. All over the web people say between 72-76cc on the '85 L98 TPI, which was because they were 'Smog Heads'..
Well that certainly sheds new light. In the Summit catalog they say that a 64cc chamber with my flat-top pistons yields a 9.7 CR. I must be running high 8's with these smog heads. I guess it's time to start shopping for new heads.
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