Ok so im getting a set of 906 vortec heads of my buddy for pulling his motor an transmission outta his 2nd gen the head ms are outta a 98 vortec 350 he says the heads are in good shape no smoke when first starting up i wanna use these heads for my hsr setup im doing on my 383 build i need info on these heads an what max cam lift i can use. Also what a good rockers i could use as well

 

Max vortec lift on unmodified heads is usually between .470-.480. Best way to go is have the guides cut down to gain more lift. Some people, including myself, use GM LS6 springs with comp retainers. This combo is supposedly good to .550 lift with no machining. Either way, you should always measure. Im running .502 lift with the ls6 springs and have had no trouble. I didnt measure though (stupidly). Use the search feature and you can find enough of these threads to read till your eyes bleed.

 

Find your total distance between the bottom of the valve retainer and the top of the valve stem seal. Then subtract the minimum clearance of like .060 And that how much you can run. There are some variations in the castings, even with .060 removed from the bottom of my retainers (the ghetto grind but on a lathe) my max was .550 so I felt I was good for a max of .490 just on the slim side. The speed shop would not recommend that was enough. They wanted a total of .100 clearance so I had more machined off the valve seal area. Now they may have soaked me for a few more bucks but I am good to at least .550 lift. I think comp cams springs recommend .060 between coils but you can verify that on their website.