Don't bother with the 243s on a 5.3. The 5.3 has a small combustion chamber so it's better to go with a 5.3 casting with 2.0 or 2.02 valves and have them milled. If you go with 243s you lower compression, yes you can mill them but you will only get back to stock CR. TSP has some nice stage one 5.3 heads, with good springs for like a little over 1000.00 and they will mill them for free. I have seen several people use 64cc heads on 5.3 engines with no gains. If you have a NBS you can use the stage I 243 casting with a .030 mill and you should see some good gains.

 

thanks for the tips man. The problem is well...I'm broke and patriot sells assembled 243's for $425 than all i'd have to do is mill them down and buy push rods and a cam. i was told that a .040 mill on them would give me just a hair more than 62cc. Alot of people may say if your not gunna do it right then don't do it at all but i would spend twice that on rebuilding my heads with bigger valves/springs/milled etc right? I'm obviouslt not very cam/head smart but i dont see why the 243s wont give me a nice gain.

 

I had my heads P/P for 500.00 and bought manley 2.0 valves for like 90 buck just the intake valves. The person who does your heads can mill the heads and install the valves and springs. The 243 casting is a good casting, but not for the 5.3. If you are going to go with a 6.0 just save that money and invest it on the 243, but worked heads with good springs and valves. If you buy the stock 243s you still have to invest some money to increase flow and upgrade valves and springs. It's easier to buy them already worked and ready to install.

 

patriot will weld the chambers shut and report them to any CC that you want. so you can get a 243 head with 59cc without milling them any at all.

 

So they can make you a stage I 59cc 243 head and you can mill them further?

 

would an 07 classic have the 243s or is it just nnbs, id check myself, but its nowhere near me

 

Bad IDEA stick with the GENERALS HEADS!!!! Those Patriot knock offs are not real and soft enough you can spread them with a butter knife.