Lt4's came with aluminum 1.6s and they were designed to be driven daily
"designed" yea maybe,the more correct term would be it was cheap and passed our safety factors so GM produced it.
well have you ever heard of a thing called engineering metallic fatigue?
under a cyclic load and with high temperatures present in the cylinder head it can cause fatigue in a lower strength metal such as Aluminum, not only that but aluminum also has both lower possions ratio and lower shear and elasticity moduli
This leads to rocker arms failing at the fulcrum, I have seen happen many times, on "quality" aluminum rockers such as the Crane gold.
Let me give you an example a plain jane 1040 Steel alloy has a Yield strength rating of 60500 PSI, while the hardcore 7075 Aluminum alloy has a yield strength rating of 15000 PSI, huge difference.
my point is these aluminum parts e.g. rockers or connecting rods are meant to be used in short bursts, like a race car, there is to great a chance of failure if used normally for long periods of time on cyclic loading.
Im not saying they wont work, but I wouldnt put them in my car
97 Trans Am WS6
, LT1 factory 4bolt freak, M6, FLP LTs, Cutouts, Flowmaster catback, Accel 300+wires, Jet Airfoil, K&N air filter, Ferco Bellows, MSD Opti and Coil, Beehive Springs, CAT 1.65 Steel Full Roller Rockers
68 Firebird 400
, YC 400, Hbeam rods, ported 670 heads (2.11i, 1.77e valves), 1.65 RRs, Torker 2 intake, Nodular Crank, Eaton Limited Slip, 3.55 gears, M20 M4
65 Impala SS
327 Camelhump Heads, 650 carb, M20 M4 12 bolt 3.73 gears
91 Jeep XJ 2 door
. 4X4 NP 231 TC, AX15 M5