2004 Slingshot Yellow
So interesting Greg, Thanks for posting!Very interesting testing done on three stock LS heads. Stock 5.3 706 small valve heads come out on top on a modified 5.3L LS.
Surprising HP Numbers From Our Stock LS Cylinder Head Test
I knew you would comment!! I agree this test is pretty one dimensional but, the point is it kills the fantasy of using LS3 or other LS factory heads on the 5.3 to improve performance. The right aftermarket heads and cam really wake up the plentiful 5.3 engines, that's why its one of the favorites for the Street Rod crowd. Thanks for the tip on the heads, will file that away.If you get serious about making some power with your 5.3, there are some very good heads available from TFS that were developed just for that engine. They are the GenX 205 and offer 58cc combustion chambers, so you have a compression increase instead of a compression drop, like all the factory heads deliver. Compression is a very important component when it comes to performance. The flow improvement is impressive, with the intake @ 284 cfm @ .600" lift and the exhaust @ 228. Compare that to the stock head @ 231 and 193 at the same valve lift.
These heads are designed to work with the small bore of the 5.3 and that also is critical. That's another reason that the other factory heads performed poorly. The valve shrouding from the small bores impacts the flow of the larger factory heads. If all the factory heads were tested on a 4" or larger bore, the outcome would have been different.