Corey carefully honed the new guide. He set the clearance at 0.0014 inch on all guide
There was a big push nearly 40 years ago when unleaded gasoline was introduced to modify the cylinder heads. It was said that a Pontiac and other cylinder heads would need to be fitted with steel seat inserts or the valves would burn from the unleaded gas. The same was stated about installing bronze valveguides. As we now know this is not true. That myth needs to be finally put to bed, especially when production Pontiac cylinder heads are getting harder to find.
Surfacing the Cylinder Head Deck
 Here the valve-seat area is being cut. The intake angles are 45-degree seat, 60-degre
Part of a proper head rebuild is to surface the deck to make sure it will be parallel with the deck of the block. Often this step is overlooked, along with the fact that the finish of the deck needs to be approximately 30 RMS for cast-iron and 60 RMS for aluminum, the same as the block. The amount of material removed needs to be recorded because on a V-style engine if more than 0.010 inch is machined off, then a correction for the intake manifold will need to be made. If this is not done, the intake manifold will not seal properly and can cause either oil or air leaks, or both.
When manifold correction is required, the proper approach is to modify the cylinder head surface instead of cutting the intake manifold. This way an out-of-the-box intake can be used and different manifolds can be tried. On a standard rebuild, a small “clean-up” cut is recommended and will not create any sealing issues.
 A valve-height micrometer is a fast and accurate way to determine the distance from t
When a higher compression ratio is desired, the cylinder head is milled to decrease the combustion chamber volume to alter the static compression ratio of the engine. For this to be done accurately, the cylinder volume with the piston at TDC needs to be measured, along with the volume of the combustion chamber and head gasket. Once this is determined, the head can be milled to a desired combustion chamber volume. This is a tedious task since the machinist needs to cc the combustion chamber with the head on the decking machine. Through experience, they will know more or less how much material to remove. As they “sneak-up” on the final dimension, the combustion chamber volume may need to be measured a few times. If an excessive amount of material needs to be removed, a procedure called angle milling can be performed.
The installation of the necessary angles on both the valve itself and the seat is the valve job. Since both valves spend more time traversing their lift range than dwelling open, the angle and accuracy of the valve job is paramount to the performance of the engine.
 RaceKraters carefully machined the spring seat area so that no shims would be require
Low-lift flow on both the intake and exhaust valves is dramatically impacted by the valve angles. As the valve moves away from the seat and combustion chamber wall it becomes unshrouded. The valve angles become less critical, but still play an important part in the air throughput of the engine.
The head shop is used to cut the angles into the valve seat, and the valve grinder imparts the proper shape on the valve itself. A common performance procedure is a multi-angle valve job. By integrating more angles into the seat, the airflow is increased by gently steering it instead of forcing abrupt turns.
 Each Comp Cams valvespring was tested and the pressure at the installed height of 1.7
Contrary to popular belief, most cast-iron cylinder head Pontiac engines came from the factory with only a one- to two-angle production valve job. This was due to the use of an integral seat and a cost/benefit ratio for manufacturing. Back in the day, many cars that were sent to the press fleet and were tagged as “ringers” had much attention paid to the valve angles. The difference between a cheap and high-performance valve job is the amount of effort taken to create the angles.
Porting of a cylinder head returns the most bang for the buck, especially if the camshaft and intake manifold are also changed. Reshaping cast-iron is a very tedious and time-consuming task and is one of the reasons most performance cylinder heads are made of aluminum. Others are cost, weight, and heat dissipation.