A quick question before I order: The TPIS ZZ-409 cam has an advertised duration of 287/287 226/226 @.050 with a .520/.520 lift and 112 LS. The .520 lift was with 1.5 rockers, and TPIS says that with my 1.6 rr the lift will be .554. My question is, is this too much lift with flat tops with valve reliefs, will I run into clearance problems? I believe I read somewhere clarance is fine up to .575, but I'm not sure where I read that at, it's been a while. Does anyone know if I'm right on this? Any input would help. Thanks guys

 

this is what someone told me on this subject:

"max lift on stock vortec heads is 480 -485 lift .you have cut off the top off valve guide for more guide to retainer clarence."

Does anyone know if this holds any truth?

 

Yeah, that's true. The spring retainer will have clearance issues with the top of the value guide when you get up near .480. No big deal, have a shop clearance em when they are cutting the larger spring seats you're going to have to get to run springs good enough for the lift you're talking about. Can't help any with the valve to piston clearance thing...

 

ok I just did a set of Vortec heads the other day, this is what I saw...#1 the lift before guide to retainer interfence is about .525, but coil bind on Vortec springs is about .480
#2 The bottom OD of the guide top is larger than the ID of a normal 1.250 valve spring, so you have to machine the bottom of the guide OD on the topside of the head. A normal "Z-28" spring will not fit over the guide boss!

 

I read on another thread about TPIS selling a spring for vortec heads that works without machining the head and is good for over .500 lift. I would ask them.

 

I'll do that, thanks!