69 Z28 302 Crossram Pg. 5
With the short block wrapped up, it's time to turn our attention to the cylinder heads.
The cylinder heads used on this engine were a pair of 1969 vintage "186" castings, which are the correct castings for a 302 engine. However, this particular pair of castings actually started out as a more pedestrian set of passenger car heads which were originally equipped with 1.94"-1.50" valves. While some purists may scoff at the thought, given the scarcity of original 2.02-1.60 valve heads that haven't been hammered to death, starting with a pair of 1.94 valved heads is actually a preferable alternative. Using these castings allows the user to open the seats up to accept the larger valves, thereby starting with virgin metal to cut valve seats into. Original 2.02 heads with sunken valve seats are nearly impossible to repair since there's very little room to cut them for hardened valve seats without cutting into a water jacket, thereby ruining the head.
Again, before any machine work was performed, the castings were magnafluxed to ensure we weren't going to end up with an expensive pair of bookends. Next, the deck surfaces were checked for straightness, and again, everything passed with flying colors.
The heads received a full set of bronze guides, and the tops of the valve guides were trimmed for additional retainer-to-guide clearance and to allow the use of "PC-style" valve seals. Instead of the more traditional teflon seals, a set of K-Line seals were installed as I personally feel they do better job of oil control in the long run.
Once the heads were machined for the larger valves, a plunge cutter was used to open up the valve bowls to help blend in the ridges left by opening up the seats. The seats were then given a 3-angle valve job. (No porting of any sort was done to the heads)
The final machining step was to remove the factory pressed in rocker studs and convert the heads to use screw-in studs and pushrod guideplates. It is worth noting here that despite what many believe, original `69 302 Z28 heads did not have screw-in studs and pushrod guideplates from the factory. However, this is considered a worthwhile conversion, even if it's not 100% "factory correct".
Once the heads were machined, a new set of stainless steel one-piece 2.02"-1.60" valves were installed, the valve spring installed heights were set, and the heads were assembled.
Nothing trick here, just good quality factory performance cylinder heads and quality machine work.
K-Line valve seals were used instead of the more traditional teflon components as I feel they do a better job of oil control in the long run...a must for a street engine!