Hey everyone, i am new here. I also looked through some of the older threads to see if anyone had any information that could help satisfy my ideas. And if i am asking a question that someone has already posted and answered i apologize in advance and hell- maybe someone can point me in the right direction then. Currently i have a 1991 Z28 (it has not ran or moved for 7 years- kids will do that to you ) I have been working on it here and there and finally i am down to planning my build. I have seen from many others on here that the Vortec HSR intake is a good combo with the vortec heads that GM makes. I have decided to go this route, my only reserve is that when it comes down to the cam i pair them up right. I am looking at the GM part number 12558060 (taken off the heads) they are cast iron heads:
170cc Intake Ports
64cc Combustion Chambers
1.940'' Int/1.500'' Exh Valves
.475'' Max Lift

Those are the specs. I am pairing these heads with a LT4 Hotcam- Imagine that.... lol i see that there are alot of people doing that so i am sure that it is possible .525 .525 with 1.6 rocker arms.. I want to know what modifications to the head aside from the obvious springs would be needed to ensure this combo works minimizing the chance of damage.. I am after details on what machining will be needed if aside from springs if any at all. I need some good feedback and some ideas. I happen to have a set of these heads laying around and a hot cam that i aquired from a wrecked 4th gen (LT1 motor- I knew the owner) that was getting junked.. Anyways, like i said if i am in the wrong place and someone has already posted a thread that will answer my questions then please point me in the right direction, if not the fire away i am open to new ideas and suggestions. Thanks

 

Take them to your local machine shop. I know for starters they need set up for screw in studs.

 

Having your guides cut will be an easier route, but you can also check out a place called Alex's parts. They have some vortec springs that can allow up to .550" lift. I am running these springs with a .540" lift camshaft. I have heard others also choosing this route and not having any issues. But as mentioned above, screw in studs are recommended and at that point should get your guides cut as well.

 

http://www.alexsparts.com/valve-spri...rf-hyd-roller/

 

Since you dont have the heads installed, I would go ahead and get the guides cut and screw in studs installed.

 

I installed CHE bronze guides on my vortecs. Im running .563"/.578" lift with zero troubles.

 

Very impressive. First person i've seen on this board running a bigger lift than me on vortec heads,lol. Any 1/4 mile times with that?

 

All very well but little to be gained with higher lift on unported heads
Vortecs max @ .500 ; their big attraction is the excellent flow rates at lower lift numbers

 

I just reworked a set of vortecs. I used Comp springs (#26918) #787 retainers, and Crane +.050 valve locks. This allowed me to get VERY close to the recommended 1.80" installed height(1.795"), This combo gave me .590-.600 retainer to seal clearance, for a safe .550 lift. No valve guide machining necessary. I DID, however, get the threaded rocker studs installed. There are some minor variances between heads, of course.

 

I appreciate the charts, and actually what you said was a very common response i got before i put the camshaft in my car which at one point almost swayed me not to run the setup i have now. But i would also have to disagree with you. My heads are not ported, and i ran 12.97 with a .490" lift camshaft and 11.91 with .540" lift cam. I'm going 100% off of what i personally have experienced. There are plenty of people who also vouch for the lift of vortec heads actually being better up to about .550" where at that point they do to taper off pretty drastically. But then again i'm sure there are people who experience the opposite. I'm no professional on vortec heads, i just know what personally worked for me.

 

What was the duration on the bigger lift cam? If its not the same duration that came with the smaller lift cam your not making equal comparisons. However, you should always run more lift than what the actual head peaks at cfm wise because of the area under the curve. It is just an air pump and .500 valve lift is not the "biggest" I've seen on vortec heads that's a fruit cam if you ask me

 

heres a good read on vortecs.
http://www.chevyhiperformance.com/te...t/viewall.html