I have read and researched this topic and have read some info and I want to put this to bed for good. From what I have read these two heads are alike in everyway except the combustion chambers. The 243s being 62 and the 317s being 72cc. I have also read that the 317s have longer runners that aid more in low end tq. The plan is to mill some 317s to a 64cc chamber and port/polish the intake and exhaust, unshoud the valves, and a 3 angle job on the valves. Someone break down exactly the differences between the two, not what you think but some hard data to back it up. What I have read might be wrong but I am trying to have a matched combo. Thanks

 

243's are a 64cc chamber.

 

what are u plannin to do with them ? what engine are they goin on ??? need more info

 

check out the ls1 page on smokemup dot com. They have the Genn III head specs there - flow #s, valve sizes, port volumes, chamber volumes, all by casting number.

 

LQ4 iron block with LS2 rods and pistons with the standard crank, 220/226 cam .605 I .600 E on a 112 LSA, 10.7-1 CR, TBSS intake, and either 317 or 243 heads ported. 317s will be milled to yield a 64 cc chamber. I will be shifting at 6200 with a 6500 rpm redline. The stall will be a 2500 in my 1500 HD. It has a 4L80E and a 14 bolt with 3.73s. I want as much lowend torque and midrange.

 

Anyone else have any input? I would like to get as much info as possible. I looked at the above link and didn't see what you were talking about

 

http://www.smokemup.com/tech/ls1.php

 

The only thing that says is that the valves are lighter on the 243s and they out flow the 317s stock.

 

n/m me lol been drinking a bit today lol

 

I don't think you can mill the 317s that much. I think you can take them down to about 68cc. Personally I would go with the 243s.