When i was looking into 243's....even milling down the max, the compression was still going to be lower then my stock 862's. Was the only reason i got a set of those worked/milled down to raise compression above stock.


Lambo is running 862's and I THINK he's one of the fastest 5.3's. His guy is doing mine too. If the block was a 6.0, by all means, 243 will flow better. Sure most of you guys here know more then me, but few months ago I did tons of research and talked to a few machine shops, and they all agreed 243 would make me slower, and recommended working factory heads IF staying n/a. I went with a milder cam, so that could be part of the reason as well.