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i have heard that a vortech head must be modified in order to run high lift cams. is this true? how big is too big? what modifications will need to be done? is there a special spring that needs to be used?
thanks for any info guys.
 

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If you go over .475 lift the stock springs will stack or coil bind. Also a chance of the retainer hitting the top of the valve guide. As far as springs go use the springs recommended by the cam mfg.As far as modifications you probably should have the rocker arm studs either pinned or put in screw in studs. The from what I've read, you're going to have to have the guides cut down. Also I think the rocker arms are an issue with the slot not being long enough if you go too high in lift. But I think Travis on this site runs a .480 comp cams with these heads. I run them, I have a 330 hp crate motor and I swapped the cam to a comp xtreme energy 262h and it has .469 lift on the exhaust and I dont have any problems

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Black 69 camaro
 

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Right on! The stock valvesprings are weak, and the retainer to guide clearance is pretty tight. I run a comp cams XE268 (.477 intake, .480 exhaust) with the matching 981-16 springs, retainers, and locks. I've got over 2 years on this combo now and it still runs great. I am also running stock gm guided rockers (required with these heads unless you machine them for screw in studs and guideplates). I keep hearing about the retainer to guide clearance being about .475, so I am apparently right on the edge. I figure either production tolerances, or maybe the stock rockers being slightly under 1.5 ratio are the only reason I am getting away with this (I really should have measure the clearances but didnt). I have refrained from installing these new 1.52 or 1.6 magnum roller tip rockers (thats another story on why I have both) for this very reason. Of course, it may just be the design of the comp cams retainers giving me a little extra clearance. All I know for sure is that it works.

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375hp 78 Chevy truck
77 Chevy Nova
95 Chevy Lumina 3.4L
and building a 78 Nova
 

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To add to the above post...for whats its worth...if you want to run something bigger than a .480 lift cam, you might be better off going with some dart or trick flow heads. Either can be had for under $900, and they already come with good springs, screw in studs, etc. By the time it was all said and done, I could have spent the same amount of money on a set of these heads and had the potential for more power. If you already have a conventional pattern intake, aftermarket valve covers, and roller rockers, then you will save money by not using the vortecs. I have been real happy with mine, just wish I would have known all the facts up front.

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375hp 78 Chevy truck
77 Chevy Nova
95 Chevy Lumina 3.4L
and building a 78 Nova
 

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i am running .525 lift with my vortecs, wth 2 summers on it(about 10,000 miles). i didn't get the guides cut down- but i got them used from a circle track racer, and he had modified them for screw in studs, so the guides may have been cut. i like them, but i am wanting more power, so a set of AFR 195's may be on the way.

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1971 Nova(looks like 69 camaro from underneath!)
355sb, vortec heads, HOT cam,T-10 tranny, 3.70 gears 16" IROC wheels
 
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