LZ9 = 3900
LZ4 = 3500vvt
LX9 = 3500
3.9vvt and 3.5vvt are NOT the same engines. Block castings are different, heads are different, intake setup is different. 3900 also has oil jets underneath all 6 pistons, hence the oil cooler. All other 60* enigne only have oil jets under pistons #1 & #2. Fiero guys have tried mixing and matching other 60* manifolds with 3900 heads and nothing fits. As for exhaust, custom is the only way, as Sexy pointed out... (Pretty sure the LZ4/9 manifolds are not the same either...someone correct me if they know FOR SURE that this is not correct. 3900 exhaust manifold mounting surface has a different angle than all the other heads.)
Last edited by DomestikDemon; 11-30-2013 at 08:23 AM.