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

 

Are they just stock 243/799 heads?

 

yea just stock no port work

 

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.

 

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.

 

I would also mill the heads about .30 to get the compression ratio back up on the lq4 to like 10.5:1

 

If the heads aren't on the car yet.

 

was the compression higher with the 853 or is it higher with the 243 or the same

 

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?

 

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.

 

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

 

so question is whats is my compression now with the 243 head and stock head gasket