the retainer has a different shape which raises the point at which it stops the spring

 

I think I understand what you are thinking but it doesnt relate with the main issue of clearance and the stock vortec head. The clearance problem isnt related to the valve spring seat it is related to the height of the valve seal and the bottom of the retainer(you could leave the spring out to measure this clearance)

 

i do not want to insult ur intelligence but the way you are describing the valvetrain is a little off. the retainer connects the valve stem to the top of the spring. the spring simply sits on the spring seat, and the seal sits on the seat, and only keeps oil running down the valve stem into the chamber, its not actually connected to the valve itself, nor the retainer in any way. also, the seal will never cause a problem, valve stem seals are usually like 3/8" tall, the spring will bind way before seal clearance becomes an issue. there are only 2 clearance issues you need to worry about, spring binding clearance, how far can the spring be compressed before its coils are touching, and valve/piston clearance. the piston will slap the valve if the lift is too large and the valve gets pushed out too far into the chamber.

 

The seal dosnt actually sit on the spring seat it is a posi style seal of a larger diameter that goes on the end of the valve guide. When the valve is opened the retainer travels down with the valve toward the valve seal. There is no question to the fact that the retainer valve seal clearance is an issue when you increase valve lift over stock in a vortec head.

More than you ever wanted to know about the vortec head http://www.nastyz28.com/forum/showthread.php?t=56505

 

then your vortech heads must have, not only tall seals, but unnaturally short springs. im no vortech head wiz, but even the SBC assembled heads ive played with in shops have almost a full inch between retainer and seal, and in a car that generally has less than half an inch of valve travel you shouldnt run into problems. this all just sounds very weird to me

 

I dont remember exact but jukyard stock mine measured .510 - .060 = .450 overall lift capacity(worst one). I did the getto grind to the retainers for an additional .02 inches of clearance. I ported the exhaust and have been pleased withthe headsthe only issue I have is my headers do not match well with the exhaust ports and have some gasket problems but I hope to resolve this with a different set of gaskets.

 

yeah, thats what i was saying. the springs can only compress about a half inch before the springs bind and the rods snap. this should leave at least 3/8 inch gap between that retainer and the spring seal.

 

So you are saying I should have .875 inches of clearance total bwtween the valve seal and the retainer? [8D]

 

total uncompressed, somewhere in that neighborhood. like i said, never dealt with vortec heads specifically, but ive never seen springs that have an installed height of only an inch or so

 

however, if you have specific experience with these heads and the retainers DO in fact interfere with the seals around half inch lift then I stand corrected.but in all of my experience the spring bind height and piston clearance are the only things to worry about.