Lance, I've used the vortech head on a couple of engines, and they are 3/8" studs. As far as rocker upgrades, it's a great idea to go to the 1.6's, but I'm not gonna dare recommend one over the other, because I don't know what fits the center mount valve covers. I like the ultra pro mags, simply for the weight out over the spring. I welded tabs on my heads to utilize perimeter bolt valve covers, because I went with Crower shaft mount rockers. These were race engines, for a steel headed circle track class. Again, I'm no help...
FWIW,
I have 1.6 aluminum Proform rockers on my 406 w/vortec heads. It's a solid roller and I have beat it up pretty hard, no failures in the last 9+ years it's been running.
I believe mine were 3/8. I have taller valve covers on them. I do believe they hit the valve cover at the corners (front & rear) so I had to grind them down a little where their square edge is. I suppose this can change based on the exact valve cover used.. Mine were some billet aluminum ones.
But please, before you switch ratios check your valve to piston clearance and also your valve springs for coil bind! Going from 1.5 to 1.6 will make the valves open further so you need to make sure the valves are not going to hit and springs are not going to bind. Don't rely on what some magazine says will work, they are not going to fix your engine if it goes wrong. I would hate to see you install 1.6 rockers only to bend some valves or break some springs and be sidelined for the season from engine damage. It can get pretty expensive to repair that damage.
__________________ Steve Hayes
"Dust Off"
68 Camaro
Speed has never killed anyone. Suddenly becoming stationary, that's what gets you! "Jeremy Clarkson"
I think I have a couple sets of 1.6's that will forever be un-used..... and since they're not the self guided --- they would require "guide plates" which I think I also have a couple sets of -- If you'd like -- you'd have to wait until I'm home from my trip to the USCA event and I'll check to see what's laying around and they'd be FREE to you if you wanted to use them.
What you'd then need to find out is if your heads will take guide plates.
Thanks for the most generous offer Greg. From everything I've read, adding guide plates to a stock vortec head is a no-no... In order to go that route, machining on the head needs to be done as well as opening up the pushrod holes. I'd prefer to not crack the seal so speak right now, so my only choice right for the time being will be self aligning rockers.
Sounds like rockers for 3/8s studs are needed and my tall valve covers should clear most sets with minimal or no clearancing needed.
__________________
Lance
1985 Monte Carlo SS Street Car