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Old 01-05-2009 | 03:26 PM
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Default ls1 heads

What is the differnce other than the valve cover bolt pattern for the ls1 heads between 97-98 and 99 and up, i have been told that 99 and up heads flow better? why is that if its true
Old 01-05-2009 | 06:31 PM
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nothing! unless that person is talking about flow in general due to 01 and 02 have the ls6 intake. but if just the heads then no.
Old 01-05-2009 | 07:08 PM
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I always heard that the 97-98's didnt flow as well as later heads?
Old 01-05-2009 | 08:26 PM
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241s were media casted as opposed to sand casted which results in a smoother intake runner. that is all.

Last edited by Shawn MacAnanny; 01-05-2009 at 08:34 PM.
Old 01-05-2009 | 08:27 PM
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1997-1998 ls1 pn# 12559853 comb chamber vol. 66.67 in/ex 200/70 cc

99-03 12564241 66.67 in/ex 200/70 cc
Old 01-05-2009 | 10:23 PM
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so if im understanding this correctly, the 99 and up heads were just casted differently resulting in better flowing heads.
Old 01-05-2009 | 10:39 PM
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In random testing the sand casted heads have been about 5 to 7hp down from the SPM (semi-permanent molded) heads. That really is the only difference in the LS1 heads.
Old 01-06-2009 | 09:50 AM
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im almost sure that you mean the ls6 heads when you talk about the spm and sand casted.
Old 01-06-2009 | 01:20 PM
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What about after porting? any difference?
Old 01-06-2009 | 02:49 PM
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I'm positive the heads up until 241s (late 2000) were all sand casted. Since 243 heads werent cast until them i am sure they used the same media (i forogt exactly what it is) would be used for the 243s also.




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