as long as the af and timing is good at idle not to many idle tables have to be changed

 

i thought 243 and ls6 heads were the same....the ls6 having sodium valves...arent the combustion chambers on the 5.3 heads smaller than the ls1's too?

 

243 heads are on ls6's and ls2's..the z06 that had 243 heads had sodium filled valves..

 

yes and yes, but according to the charts they flow the same. thats why ppl do the 5.3 head mod and have 2.0 intake valve installed. so somehow the 5.3 with a smaller valve flows same as ls1s tht have larger IV

 

but i wish you could have tried to tune my cam that was in my ls1. that thing was a bitch. one day it would run fine then the next day it wouldn't idle for nothing. i guess that is why lingenfelter stoped making it. it was only a 218/229 560 lift if i remember right and on a 113 lsa but somethng about it made it hard to tune. of course i had it almost dial in right before my truck burnt.

ok back on topic

 

Quik, the only issues that take some time for me are the drivability issues like startup and surging, other than that, it's pretty easy to do everything else.

 

Edit Quik pretty much covered it, these heads are great for big cams. Eric is an internet forum reader, he has alot of "ideas" in his head but hasnt had any real tangeable experience with LSx motors. He knows his **** on trannys but some of the stuff he posts on GMFS is almost laughable at times.

If you move a valve through the highest flowing point of lift for the most amount of time the more air oyu are going to flow. For example most 5.3 heads flow well up to about 550, if you run a 575 lift cam you go through peak flow once going up stay close to it at peak lift then go back through peak flow with the closing of the valve.

Sportside didnt gain much switching to LS6 heads because his compression is about the same as stock and teh LS6 heads dont flow too much better then the 5.3 heads.

 

then why are some of the tech guys claiming 15hp gains just by switching to 243 heads? why is the demand so high if a 5.3 head will do the same. i was looking at patriots cnc'd ls6 heads at 59cc chambers. im i looking in the wrong direction?

 

Of the commom Lsx stock heads, the order of flow according to smokemup.com is:

5.3 < LS1 (barely) < 6.0 < LS6. There is quite a bit of difference between a 5.3 head and a LS6 head especially at higher lifts, ~25 cfm intake @ .500 lift and above. Of course 5.3 heads have the smallest chambers of all, so to use any of the other heads without losing compression they would have to be milled. I don't think you could mill a 6.0 head down from 72cc to 61cc without running into intake fitment problems. Richard from WCCH told me the max they mill is .050. Using the general .006 = 1cc for a LSx, you'd have to mill a 6.0 head .066 to get the chamber down that small.

I agree with Cody, regarding the max lift. I really wish that Comp would publish a graph of lift v. duration for their lobes. It would make explaining cams and valve events alot easier to actually plot out what the intake and exhaust valves are doing during one crank revolution.

 

OK so why is the ls6 head shoing better flow numbers than the 5.3 even though they have the same size exhaust valve?