Wanted to highlight these things I learned along my journey:
1) Another difference between Vortec valves and the earlier non self aligning head valves is the tip length. Earlier valves are 0.250" on both intake and exhaust valves. Self aligning head intake valves have a 0.260" groove-to-tip length, exhaust valves use a 0.289" groove-to-tip length. That said, the typical SBC valve tip length of 0.250" will work just fine with self aligning rockers. Like with ANY rocker arm/valvetrain combination, the
valve train geometry
needs to be verified.
2)
Note: On Vortec and other heads using self aligning rocker arms, using a +0.050" lock can cause interference between the rocker tip and the locks/retainer. Rocker contacting the locks/retainer has been encountered using a combination of c/n 906 Vortec heads, Comp Pro Magnum rockers p/n 1317, Comp retainer p/n 787, Comp spring p/n 26918, and the +0.050" locks.
The engine builder must mock up the assembly and check the clearance closely. In the case there's insufficient clearance, there are a few options:
- Use non self aligning rocker arms. Requires guide plates be installed.
- Use longer valves
- Use a different spring/retainer combo that uses a standard lock
- If just the locks are hitting the rocker, using a shorter (lash cap compatible) lock like the Edelbrock p/n 9615 may help. This 7 degree lock is 0.050" lower than a regular lock.
-
Use extreme caution if making the spring seat any deeper.
I contacted CompCams and their response was that they have not heard of the problem as I described.
3)
The Vortec head features a very large boss at the base of the valve guide that measures 0.850-inch in diameter and is used to locate the 1.250-inch outside diameter (O.D.) valve spring. The head uses 0.560-inch I.D. seals mounted directly on the top of the guide. This guide boss is also very tall. This height restricts the room between the top of the seal and the bottom of the valve spring retainer at max valve lift. There are two simple approaches to modifying the head to accept a performance valve spring that will create the room necessary to allow greater valve lift.
4) The second solution is less expensive but requires more effort and to purchase a machine tool to modify the valve guide boss to add clearance. COMP sells a slick little tool that will machine the guide down to a 0.530-inch O.D. seal size while also lowering the boss height. The boss height of our heads measured 0.730-inch from the spring seat. It is this height that minimizes the seal-to-retainer clearance. With the tool set up in our ½-inch drill motor, it took a few minutes to machine all 16 guide bosses, being careful to lower the guide height only enough to create 0.550-inch retainer-to-seal clearance.
I found these (4) bits of info on the internet and cut/pasted them here. Hope this helps.........
