Like intake manifolds and carburetors, it seems that valvetrain components are commonly replaced for a myriad of reasons, and at its heart is the camshaft. While some hobbyists perform a cam swap hoping to increase their Pontiac's performance, others may be looking to improve street manners or simply replace a worn unit. Whatever the reason, camshaft replacement is certainly a time-consuming and tedious task that requires a specific break-in procedure.
With the recent oil reformulations, flat-tappet lobe failure has become a great concern for hobbyists and camshaft manufacturers alike. This situation is just one of the reasons surrounding the recent popularity of more-costly roller grinds, but since hydraulic flat-tappet units contain such great low-buck performance, they remain a popular choice for budget builds. If broken in and maintained properly, they should offer many miles of reliable performance. Follow along as we replace our Pontiac's flat-tappet camshaft with another in a weekend, and incorporate one professional engine builder's technique for successful break-in.
Camshaft Basics
The camshaft in a Pontiac engine is responsible for driving the mechanical fuel and oil pumps and ignition distributor, but its primary function is controlling valve action. A tappet (or lifter) following the shape of the lobe uses a pushrod to transfer its motion to a pivoting rocker arm ultimately lifting the valve off its seat at a specific crankshaft angle.
Types of camshafts available on today's market include hydraulic and mechanical (or solid) flat-tappet, and hydraulic and mechanical roller-the operational characteristics and attributes of each can be found in "Top 6 Cam Questions Answered" (HPP May '07). Other than the mechanical units in the early '60s Super Duties, all production Pontiac V-8 engines utilize hydraulic flat-tappet camshafts, which rely on pressurized engine oil to maintain minimal valve lash.
As we learned in "The Slippery Truth About Oil" (HPP June '06), oil manufacturers have reduced the amount of high-pressure anti-wear additives found in most passenger car oils that minimize metal-on-metal contact of the lobe and lifter. While one might assume this spells doom for every flat-tappet camshaft in service today, simply using heavy-duty or off-road type oils, and/or incorporating a separate oil additive with each oil change may be an easy solution. But the most critical point in any flat-tappet cam's life is initial break-in and, without proper technique, any is susceptible to failure despite oil quality.
Flat-tappet hydraulic camshafts...
Flat-tappet hydraulic camshafts remain a popular hobbyist choice, due to their low-maintenance design and high bang-for-your-buck performance value. Modern oil quality concerns and sub-sequent lobe/lifter failure has, however, prevented some hobbyists from exploring current flat-tappet options. After making a few changes to the 455 engine in our '67 Firebird, we began considering a more aggressive camshaft and contacted Pontiac performance legend Nunzi Romano of Nunzi's Automotive in Brooklyn, New York. After a quick consultation, Romano had one of his hydraulic flat-tappet cam kits on its way.
It is important to note that...
It is important to note that we did not have to change the valvesprings for our particular swap. If your valvesprings are tired or if you are upgrading to a particularly aggressive grind, you will have to upgrade the valvesprings as well, which will add complexity, time and expense to the project. We planned for our swap to take the better part of a weekend, and we started early one Saturday morning. The first steps included disconnecting the battery and opening the radiator's petcock to drain its contents into a suitable catch-pan. Because our intake manifold's coolant crossover was previously separated, we were able to remove it and the carburetor while the radiator drained.
After removing the fan, accessories,...
After removing the fan, accessories, drive belts, and radiator shroud, we disconnected the upper and lower radiator hoses and automatic transmission cooling lines, and lifted the radiator away from its support. The water crossover was next. (Now is an excellent time to flush the radiator with clean water to rinse out any loose deposits that might ultimately affect its heat-transfer ability.)
Using a long breaker bar and...
Using a long breaker bar and a 1 5⁄16-inch socket, we rotated the crankshaft with the harmonic balancer bolt so the No. 1 piston was at Top Dead Center (TDC) on the compression stroke. Removing the spark plugs made the task far easier-it also gave us the chance to inspect and re-gap them.
Using a tip found in Jim Hand's...
Using a tip found in Jim Hand's book, How to Build Max Performance Pontiac V-8s, we carefully marked the distributor timing in relation to the No. 1 piston's firing position before rotating or removing the distributor. With the No. 1 piston at TDC, we used a felt-tip marker to note the rotor's relation to the distributor housing, and the distributor housing's relation to its hold-down clamp like that shown here. Aligning these marks during reassembly will ensure correct installation and place initial spark lead within a few degrees of its original setting for immediate start-up after the swap.
We removed the harmonic balancer...
We removed the harmonic balancer bolt using an air-operated impact wrench. If compressed air isn't available, remove the transmission dust cover and have a helper securely wedge a pry bar between the ring gear teeth and an area like the bellhousing or sub-frame to ultimately prevent the engine from spinning while you remove the bolt. Be absolutely sure that the pry bar is resting on the full contact surface of the teeth to prevent broken corners. The stock balancer should then slide off the crankshaft's snout with relative ease, though it may require a little persuasion with a pry bar or two larger screwdrivers.