vortec heads and max cam lift

[mobythevan]

I have seen numbers for stock L31 vortec head cam lift anywhere from .430 to .480

 

I want to run .464 lift, does anyone have a more definitive spec for he stock vortec heads?

[Tim240z]

From Scoggin Dickey's web site:

 

Our Vortec cylinder head kit provides you with everything you need to install the new Vortec heads on your vehicle. The following kits include assembled Vortec heads, head gaskets, head bolts, rocker arms, intake manifold, intake gaskets,12 point intake bolts and additionl required components as stated.

 

Stock Vortec head kits - features stock out of the box Vortec heads that are good for about 0.450" lift.

 

Upgraded Vortec head kits - features our high performance Z28 valve springs with light weight LT4 retianers, good for about 0.550" lift with a hydraulic camshaft.

 

Upgraded Vortec, Roller Head kits - features our Heavy Duty Z28 valve springs with light weight LT4 retainers, good for about 0.570" lift with a hydraulic roller camshaft.

 

 

http://www.sdpc2000.com/cart.asp?action=catalog_start&catid=2172

[mobythevan]

I came across the following on another forum and thus raised the question:

 

 

This is a quote from a recent post by Gary at GMPP...

"Two years ago we undertook an exhaustive (no pun intended) study of the Vortec head in numerous modified states with different valve sizes, throat cuts, valve jobs, port mods, guide mods, etc. We used up about 10 heads, numerous valves, and about $50,000 worth of labor. The study generated 100+ pages of flow and swirl data,which I have at my desk.

 

Here is the short version. Out of the box, .480 valve lift, 350-400 HP dependant on the CR, cam, ring seal, oil control, blah, blah, blah.

 

More than .480 lift, cut the guides down to clear the retainers.

 

........snipped

[Sleeper-Z]

while i was reading up, it varies. weird, but from head to head it changes. best bet is to play it safe and get the work done so you can safely run a .480 lift.

 

http://www.chevyhiperformance.com/howto/97458/

All of this conspires to limit total valve lift to a safe figure between 0.420 and 0.430 inch. The limitation is the clearance between the bottom of the retainer and the top of the valve-guide seal.

http://www.2quicknovas.com/vortecheads.html

The biggest issue in my opinion is the maximum lift these heads can handle when stock. I did some checking on mine and found that I had only about .460"-.470" total between the stock positive valve seals and the retainer. Add in the recommended .060" clearance at max lift and you can see the problem with anything other than a stock .400" lift cam.

Some sellers will tell you that stock Vortecs can handle .470" lift without any problem. Be careful. I don't know where they get that measurement unless they've decided they don't need any margin of error, I know my heads couldn't handle that.

 

-steven m.