I'm taking the heads off to be extensively ported and I'm going to install a bigger cam, gear drive and some other goodies...I know the valve seats have to be machined but I already did that on my Grand Prix and its a piece of cake...$50 at my local machine shop, what valve springs do I use? Cam is an Extreme Energy grind 284 but I want the springs good to .520-.530 lift. Car already runs low 13's (uncorrected) on the basically stock vortec and 268 cam setup so I wanna see if 12's (uncorrected) are in the cards with ported vortecs and bigger cam.
Chris

 

Use Comp 986, and the 1.45" retainers that go with them.

There are other issues besides the springs though; in particular, the valve guides are so tall that the underside of the retainers will hit them. While you're having the pockets machined out for the springs, have the guides milled off about .100", and have them cut to an outer diameter of .500" or .530" so you can use Comp or Crane Teflon positve guide seals.

 

I don't know that you will see a big difference in flow if you port these. That is the main reason I didn't go nuts on the intake side. I polished the exhaust side good to raise the I/E flow%, and pocket ported them to get rid of the machined ridges just below the valve seat. I have read numerous articles that these don't respond real well compared to the cost. Bigger valves are in the same boat.

 

TPIS springs p/n 700-132 drop right in without any machine work required. However, you willl have to pull the dampner out of these springs. I've been running these in my new engine without any problems. They lift to .540. I reused the stock vortec retainers and locks with no problem. Like someone already said, you will have to have the guides milled a bit as well.

Also, I agree with johnsjj2, the vortecs don't seem to respond very favorably to a lot of porting and/or bigger valves (not worth the extra money). I did the same thing to my heads that he did to his, pocket port (bowl blend) and a little exhaust work. I did replace my valves and studs, but just went with stock size Manley valves (for relaibility and peace of mind more than anything).

Hope this helps.

Mike.......

 

Well I wasn't going to go with bigger valves..but I do think porting does some good on vortecs. My buddy has a similar setup on his firebird and after he ported his vortecs and installed the 284 cam he dropped from 13.7 to 12.9. Its worth it I think cuz its practically free.
Chris