Guest jwelch Posted April 23, 2002 Share Posted April 23, 2002 I'm getting ready to put a new set of "stock" vortec heads on my 350 next week. I have a Comp. Cam #12-238-2 which has a max. gross lift of .469 with 1.5 rockers. My question is if I go to 1.6 roller rockers that puts me dead on .500" of lift. Will this be reliable? and If I go to 1.7 rockers I would be at .532 is this too much lift? I need to stay with this cam for emissions so I don't want to modify the heads to get more lift unless the 1.7 could justify the cost vs. performance. Thanks in advance for your help. Regards, Quote Link to comment Share on other sites More sharing options...
Guest kc6wfs Posted April 23, 2002 Share Posted April 23, 2002 You are going to run into coil bind at around .473. I would get the upgraded springs,retainers ect. Then you can go to .530 or so. Crane cams sells it. Hope that helps. Dave Quote Link to comment Share on other sites More sharing options...
grumpyvette Posted April 23, 2002 Share Posted April 23, 2002 http://www.sallee-chevrolet.com/Cylinder_Heads/Vortec.html remember vortec heads are meant to produce good low and mid range torque NOT HIGH RPM HP if you want over 400hp-420hp your better off with bigger port,better flowing heads I just went through this for the 10 zillionth time replaceing springs and machineing the guides so I could install a .545 lift cam on a hydrolic lifter, vortec head 383 for someone, so you guys might also use the info there are several things that effect the max lift your heads/springs/retainers can handle other than (spring bind) look at the diagram here. http://www.cranecams.com/master/vsprings.htm .read this ,a spring that will be a drop in fit for vortec heads!! Comp Cams # 983-16 and retainer # 751-16. the new Ovate wire springs by Comp Cams (the ones above) have 105 lbs. seat preasure and a rate of 410 lbs which is close to the Z-28 spring good for up to .550 lift. http://www.hotrodheaven.com/comments/messages/9058.html now with cheap springs its usually the spring coils stacking up and (binding) that limits the amount the valve can be opened but the bottom of the retainer hitting the top of the valve seals/valve guide comes in as a close second in the race to cause clearance problems so you must check that too! just adding the better springs that are normally rated at either .540, .575, .600 will give you more clearance but in most cases Ive measured the retainer /seal clearance will limit you to about .500-.510 if your just changeing the springs, and yes it is possiable to gain some clearance by useing special .050 higher notch valve locks that move the ratainers alittle higher on the valve stem but if you want to do it correctly and don,t have the measureing equip. just take the heads down to your local high performance cylinder head rebuilder and have him machine the valve guides for the .600 lift clearance and have him use these valve seal,(Hi-Performance Teflon Seals) (Machining Required) read this http://www.cranecams.com/master/vmisc.htm and this http://www.babcox.com/editorial/ar/ar79842.htm these fast burn heads are ported so don,t think the flow numbers are valid, the production heads flow worse un-ported http://www.sallee-chevrolet.com/Fast_Burn_Cylinder_Heads.html Quote Link to comment Share on other sites More sharing options...
Guest jwelch Posted April 24, 2002 Share Posted April 24, 2002 Thanks for the info everyone. I will upgrade the springs to #983-16 and stay with the 1.5 rockers to keep me at .500" lift. Sounds like this is my safest bet without going to the .600" machining and adding cost to get HP that I can't use. My motor wasn't built for the 400HP + range. I'm estimating about 320-340 without the Vortecs at the moment. Hope I've interpreted this correctly. Regards, Quote Link to comment Share on other sites More sharing options...
Guest gbvol54 Posted April 24, 2002 Share Posted April 24, 2002 Even with the upgraded springs you still have the issue of valve guide height interfering with a lift over .465 to .480 (depending on source of information). But this amount of lift is fine if you are if you are satisified with 300-400 hp and loads of low end grunt. I've also got a pair of stock vortecs and am planning on about 10-1 static CR, Performer RPM intake, Quadra-Jet carb and a Comp Cam (Xtreme 262 with a max lift of .469). Along with shorty headers this reportly will yeild just under 400 hp. More may be better, but 400 hp in a 2600 lb car should be enough to put a smile on my face. Best of luck and let me know what you decide. Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.