Yes another cam question!!!!

[RedSWB]

Recently i have been researching cams for my truck. i got the comp cams cam helper disk to help me choose the cam and see what power gains im going to get with each cam. I have heard somewhere that the vortec heads can only stand .474 of gross valve lift. Most aftermarket cams for street applications have a greater lift. Is this true or did i misunderstand something? Also is there anyway you can get away with having this much lift on stock vortec heads? Thanks again guys for your great advice!

[Fast305]

Recently i have been researching cams for my truck. i got the comp cams cam helper disk to help me choose the cam and see what power gains im going to get with each cam. I have heard somewhere that the vortec heads can only stand .474 of gross valve lift. Most aftermarket cams for street applications have a greater lift. Is this true or did i misunderstand something? Also is there anyway you can get away with having this much lift on stock vortec heads? Thanks again guys for your great advice!

Actually it is probably closer to .465" for most of the Vortec castings out there. Any more than that and you will destroy the valve stem seals and the engine will start to smoke badly.

[RedSWB]

This is for gross valve lift not lobe lift?

[Fast305]

This is for gross valve lift not lobe lift?

There are two lifts, Gross(LOBE) and NET(Valve). The .465" is at the valve. That means that if your solid lift cam runs .018" lash, you subtract that from the cam lift, multiply the lobe lift by the rocker ratio.

[RedSWB]

do the vortecs come with 1.5 or 1.6 ratio rockers?

[diadora516]

if you use the comp beehive springs and matching retainers you can get around .550 of lift i believe on stock heads. and i'm pretty sure they come with 1.5 rockers