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Generation III Internal Engine 1997-2006 LS1 | LS6
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243 and 799 heads

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Old Sep 18, 2011 | 07:27 PM
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Default 243 and 799 heads
ok just finished my cam and head swap finally. well i swap cam first and got the car tuned it a 99 a4 t/a with a (lq4 and 212/222 550/549 116+3 mac mid headers lid) i had 853 when i got it tune then i swap for 243/799 head.what I want to know is will the 243 throw my tune off enough for me to lose power. or should i get it tuned again to feel the gain
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Old Sep 18, 2011 | 07:48 PM
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Are they just stock 243/799 heads?
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Old Sep 18, 2011 | 07:52 PM
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yea just stock no port work
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Old Sep 18, 2011 | 07:55 PM
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I would get another tune but thats just me. Maybe your tuner will cut you a deal. Seems like the extra airflow would need to be accounted for.
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Old Sep 18, 2011 | 08:52 PM
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Yea I would get another tune also because the 243/799 flow a good bit more than the 853 heads that's what I would do. You may see another 30hp out of the just heads.
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Old Sep 18, 2011 | 08:54 PM
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I would also mill the heads about .30 to get the compression ratio back up on the lq4 to like 10.5:1
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Old Sep 18, 2011 | 08:56 PM
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If the heads aren't on the car yet.
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Old Sep 18, 2011 | 09:09 PM
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was the compression higher with the 853 or is it higher with the 243 or the same
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Old Sep 18, 2011 | 09:34 PM
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Someone correct me if I wrong but I think it would be about the same with the 243 heads. But didn't the lq4 come with 317 heads and the 853 come on some of the ls1 cars?
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Old Sep 18, 2011 | 09:40 PM
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Isn't the lq4 9.5:1 with the 317 and if you put the 853 or 243 heads with out milling them it would lower the CR because of the combustion chambers but I may be wrong some correct me if I wrong.
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Old Sep 18, 2011 | 10:03 PM
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LS1 heads have bigger chambers then 243/799 heads meaning you get a bump in compression going to the better head. It roughly breaks down like this (based on memory): Higher the number, lower the compression

317 head: 72cc
LS1 head (853, 241): 67cc
LS6 head (243, 799): 64cc
5.3 head: 62cc
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Old Sep 18, 2011 | 10:36 PM
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so question is whats is my compression now with the 243 head and stock head gasket
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