What's Your Problem?

Fortunately, GM Performance has recently introduced an aluminum intake manifold for TBI systems that mates with Vortec heads. The manifold (PN 12496821) is a street-performance-oriented dual-plane type that was designed with light-truck use in mind. Your existing throttle body and associated components will bolt up, but some recalibrating should be done, since these pieces were intended for a 305. Since Chevy offered the TBI system on 350ci engines from the factory, fitting the throttle body with the larger 61 lb/hr injectors used in 350 applications (305s use 55 lb/hr units) and the corresponding PROM chip would likely get you dialed pretty close. However, to maximize the potential of this combination, you might consider consulting Turbo City in Orange, California, which specializes in performance tuning GM TBI systems. Turbo City can burn a custom chip for your combination, and can also offer some guidance in selecting a camshaft for the new engine. As a general guideline, the cam selected should not have excessive overlap, and if using stock Vortec heads, lift should be kept under 0.480-inch. If a higher-lift cam were to be used, the valve guides in the heads will have to be machined for extra retainer clearance-a simple procedure for a qualified machine shop.