243 LS heads - fully assembled

[qwk_snd]

There is a diff in combustion chamber size. If they were the same a 6.0 head that's running 9.1 compression would be way lower if u put it on a 4.8, that's y they say to mill the heads to up comp. if the heads were all the same based on casting numbers 6.0s would run cupped shaped pistons, and 4.8 would need domes to make up the diff in comp because of bore size. 5.7 heads on a 6.0 will give u a bump in compression. There chambers are set up for a smaller piston than the 6.0s. Call trick flow n ask bout a set of heads that are 9.1:1 compression, and they will ask wat ur putting them on. Combustion chamber and pistion, size and type play big rolls in compression. So lol what motor did ur heads come off of?

An all aluminum 5.3 with FLAT TOP PISTONS

[Frenchy]

There is a diff in combustion chamber size. If they were the same a 6.0 head that's running 9.1 compression would be way lower if u put it on a 4.8, that's y they say to mill the heads to up comp. if the heads were all the same based on casting numbers 6.0s would run cupped shaped pistons, and 4.8 would need domes to make up the diff in comp because of bore size. 5.7 heads on a 6.0 will give u a bump in compression. There chambers are set up for a smaller piston than the 6.0s. Call trick flow n ask bout a set of heads that are 9.1:1 compression, and they will ask wat ur putting them on. Combustion chamber and pistion, size and type play big rolls in compression. So lol what motor did ur heads come off of?

I have never seen someone with both their foot in their mouth and their head up their ass. Congratulations.

[George C]

There is a diff in combustion chamber size. If they were the same a 6.0 head that's running 9.1 compression would be way lower if u put it on a 4.8, that's y they say to mill the heads to up comp. if the heads were all the same based on casting numbers 6.0s would run cupped shaped pistons, and 4.8 would need domes to make up the diff in comp because of bore size. 5.7 heads on a 6.0 will give u a bump in compression. There chambers are set up for a smaller piston than the 6.0s. Call trick flow n ask bout a set of heads that are 9.1:1 compression, and they will ask wat ur putting them on. Combustion chamber and pistion, size and type play big rolls in compression. So lol what motor did ur heads come off of?

you got your shit twisted

[AFSP1211]

Went to sleep, woke up, read this and lmao. Yes yes yes, bootlife, you are 100%correct! Continue to look for 243 heads that were only in a 6.0. -_- some people......
Think of it this way. If they had different bowl sizes, then WTF would they have all the other head casting numbers??????? There'd be no point. 243 cast is a 243 cast no matter what they put it on!!!!

[RS/SS 4.8]

243s on a 4.8 equal 9.1 compression ratio.

[George C]

243s on a 4.8 equal 9.1 compression ratio.

8.8 going by gm listing for 2010 4.8

[bootlife]

I don't know about the 243s, but a lot of heads have diff combustion chambers. My brother in law bought a 350 that was a reman n it had 305 heads on it, and cupped pistons so comp would be right, needles to say a 350 head swap was not going to work for him. I was looking in to doing heads on my 5.3 last year and the heads I was looking at had the wrong combustion chamber, they told me I could have them milled but that causes issues in its own way.

[Frenchy]

My heads are milled. Zero issues.

[AFSP1211]

My heads are milled. Zero issues.

Hmmmmm, mine too. Took .030 off a set of 241's and my shiz runs pretty darn good.

[Frenchy]

I had to mill my 6.0 243's .030 so they matched 5.3 243's.