[*]Retainer to guide clearance is the primary Achille's Heel of the Vortec. For valve lifts above .460" they need to be checked for R-G clearance. This varies from head to head. Some find they can get .480" and slightly more valve lift fine. Others will find .460" about the limit. Always check R-G with any performance cam above .460".[/LIST]
Great, I'm interested in Vortec heads, but am concerned about retainer to guide clearance. What can be done about this, and, are there any places I can buy Vortecs already modified for use with high-lift camshafts?
Good question, easy answer.
Scoggin-Dickey sells Vortec heads already correctly modified for use with high-lift performance camshafts. They also sell a complete kit which has the modified Vortecs, intake manifold (Edelbrock Vortec), rocker arms, etc to basically bolted on your existing short block.
Sallee Chevrolet has an interesting solution to this problem (from their website):
The Sallee Chevrolet solution is to use Crane Cam’s 10309-1 drop-in valve spring and retainer kit which is good for .550” lift with no machining. The installed height for this Crane Cams kit is taller and the lower part of the retainer is shorter. The “AVERAGE” clearance between the retainer and seal is .575” for this kit. We have found that some of the Vortec heads, coming from the factory, do not have the valve seals driven on all the way. You need to check that they are before installing this kit. If they need to be driven on all the way, we have found that a 3/8” drive - 1/2” socket fits the valve seal just about perfect.As with all modifications to performance engines though, you should always measure to assure that there is proper clearance and fit.
Comp Cams sells a tool that will cut down the size of the Vortec valve guide and is around $50 or so.
Another method is the infamous Vortec retainer "ghetto grind". If the camshaft being used only requires a stock 1.25" diameter single-wound valvespring, it is possible to only need to grind off approximately 3/32" off the bottoms of the stock Vortec retainers with a grinder or on a grinding wheel to achieve enough R-G clearance to run up to approximately .530" -.540" safely. I must caution here that R-G clearance must ALWAYS be checked to verify that there is in fact enough clearance - also include allowing for coil bind. One other thing - you must remove the dampner in this modification. Don't worry -- the stock Vortec valveguide being much larger in diameter than other SB heads will act as sort of a dampner and I never noticed any RPM issues related to lack of running one when I did this mod. Although myself and others who have done it this way have had no problems, I must caution this basically for those on a strict budget and cutting down the guides either with the Comp tool or at a machine shop is the best way to go. However, I'm of the opinion that since it works well within the noted constraints, then you're really only out your time to grind down the retainers. The choice is yours.
More to follow.
