243 head help

[Zzeez Rodz]

New member needs help. I have a 2009 5.3 LMG out of a police Tahoe. It has 243 heads on it. The motor was dropped and cracked the casting where the starter attaches. So I'm looking at replacing the cast block with a new GM performance Aluminum one. An LS2 6.0 block says for use with LS1/LS6/LS2 and LS3/L92 style heads only. Are the 243 heads this style. Also I bought an LS6 manifold already. Will it work with these heads also ?
Thanks Z

[SMWS6TA]

Yes you can use those (243) heads with that block and intake.

[Zzeez Rodz]

Good News, Thank You

[SMWS6TA]

My 403ci is currently using stock 243's on a truck LQ4 6.0 block.

Any particular reason on the LS2 block? LQ4 or LQ9 blocks are cheaper and have better build possibilities, only negative is they weigh 60-90lbs more (can't remember the exact weight).



The reason they state LS1/2/6 OR LS3/L92 heads is that the 6.0L blocks are a 4.00" bore that lets you use either style. But you must also the same style intake and also for LS3 style switch to LS3 style injectors.


LS3 style heads flow way more than the LS1 style heads with help build more power. You can have the LS1's port & polish to get a few more hp out of them.

[Zzeez Rodz]

Mostly weight, It's going in a 35 roadster. I figured if I had to replace the block anyway I might as well look at an aluminum one. So I thought I might want to bump up the CI also

[SMWS6TA]

IIRC the LS2 can be safely bore up to 4.010", mine is at 4.005" combine with a 4" K1 Forged stroker crank it is a 403ci.

I got a good solid forged bottom end that when able to invest again it will get a set of TF LS3 heads & I'll sale my FAST 102 intake for their LS3 FAST 102 intake.

I'll also sell my 243 heads for some extra cash.

I would recommend that you have a shop look over the heads. Now is the time for new valve guides and or milling. Also use MLS gaskets & ARP head bolts.