How To Build Max-Performance Pontiac V-8s

TAILPIPES

An efficient exhaust system equipped with good front pipes and good mufflers should let an engine perform as well as it does with an open set of headers. But how would tailpipes affect this performance? To see how the Pontiac engine would respond to smaller tailpipes, we carried out another series of tests. Several manufacturers provide larger exhaust and tailpipes for Pontiacs. We chose a 3.0-inch system from Torque Technologies to test against a typical, shop-bent 2.25-inch tailpipe set.

VALVE GUIDES

Almost all used heads will require valve guide work. The factory used simple but precisely cut holes in the cast iron of the heads for the guides. Over time, the holes wear oversize primarily due to side motion of the valve caused by rocker arm pressure. An accepted repair method was to knurl the guide holes, which when done properly, did not remove metal. Rather, it rearranged the metal for precise fit and good oiling. However, accurate knurling is very labor intensive and is seldom used today.

The more commonly accepted method to restore valve guide accuracy is to enlarge the original holes and install guide inserts (commonly referred to as "guides"). We have a choice of several replacement insert materials and types - hardened iron, thin-wall bronze, and solid bronze. All work okay, but are dependent on very precise installation. If the guide insert work is not done accurately, the valve seats will require excessive cutting to regain proper alignment.

Discuss clearances with the machinist and identify how you intend to use the engine. The type and material of the valves will also affect required clearances. We have had excellent service from the solid bronze guide inserts. Whichever guide insert you select, both intake and exhaust guide inserts or bosses should be machined for a positive valve stem seal for best oil control.

We do not recommend Teflon seals for engines to be used on the street. Teflon seals are designed to pass generous amount of oil for lubrication, and while that is great with limited-use engines, it will invite excessive oil consumption and smoking on the street. Rather, we use and recommend positive seals made of Viton. All seals must allow some oil for lubrication, but it must be controlled, and the positive-type seals of premium material work great.