Sorry, newbie mistake. I definitely meant 4.8L, it was late when I posted it.

 

go with the 243 head, you can sell your 317 heads to some one that wants to go boosted, 243's would be a direct bolt on, the 317's you would have to have them machined a lot to get the same compression..i dunno would be cheeper but the 243's would be easier in my opinion..

i put 241 heads on mine and wished i would have gone to 243 heads..

 

they flow the same

 

What thickness gaskets are you going to use on the 243 or 317 heads?

 

Don't mill the 317's, just get the 243's. That will give you room, to even mill those if you want to.

 

what CR are the 243 heads on a lq9 i know it's 10.08 stock with the 317 heads

-erik

 

The 243's flow about the same as the 317's to my knowledge. This flow chart here shows the 243's considerably better but the 317's were flowed on the same 3.900" bore when their chamber is sized for 4.000" bore which will cause turbulance and hurt flow.

 

the bore size change makes sence i assume you wouldent hav ethat problem going with 243's on a 6.0 tho cause of the larger than 3.9 bore dia.

but matched would be better than not.

 

get ported 317. I have ported 317 heads with dual spring. it flow awesome, at WOT I could actually hear it working. definately not a stock sound. Mine flow over 300cfm at 575lift. but with ls6 cam that I have now, can't at it to max it. I will change my cam soon again. to get around 580-600lift.
I do have set of 1.8rocker arms as well.

 

so I have a question, I have a LQ9 with stock 317's, if I get some 243's and get them p&p and maybe milled some, will that be alot better than the 317's??