I am getting ready to take my Vortec heads to the machine shop for prepping for my new engine and I am aware of the .480" lift limit of the factory heads. I plan on running a CC304 cam with .500"/.510" lift. I have the crane 10309 spring kit which will allow for .550 lift but I need to know what to do about the heads. Do I need to machine .03" off the valve guide or what? I don't want to screw up my lovely new heads.

Yes, you need to have the guides knocked down.

While you're at it, you might want to consider having them cut to .530" or .500" OD, and getting the spring pockets enlarged, so you can step up to 1.45" springs.

But how much is too much to knock down the valve guides. Is the .03 enough or should it be more like .05 or .10". I used the vortec heads because of their low cost. I don't want to alter that cost buy increasing the amount of machine work for the larger springs. For my purposes the smaller springs with a lift max of .550" should be plenty. I just want to make sure I don't screw up the valve guides and thus the valve train. I have done that before not realizing the .480 max on a previous engine.

It's just my experience that if you don't spell out EXACTLY what you want with the machine shop then you don't get what you want. So I need to know exactly how much to remove or the exact method of measurement to use to measure the existing guide to machine it for that .510" lift.

A better way of handling it would be to obtain the valve guide seals that you want to use, and have them leave the correct amount of material for those seals,rather than trying to tell them how much to take off. I'd recommend the Comp 503 seal or the Crane equivalent (.530" Teflon)

http://www.competitioncams.com/catalog/313.html

I will order those Comp .530" valve seals. Comp shows a 11/32 and a 3/8" size. Which size valve is in a Vortec head? Is that guide cutter on the above comp page something that most machine shops that do heads have or is that something I should buy as well?

11/32"

Most shops that do high-performance work will have cutters for that, you shouldn't have to supply the tool. In fact, if you tell them the seal part number you intend to use, they'll probably know what to do just from that; make sure you tell them you want them to leave only just enough guide for the seal to fit onto, no extra.

If they cut them down to where those seals just fit, you should have enough clearance for close to .600" of lift. Of course you can check the exact clearance easily enough after they're done.

Thanks,

I really hope this Vortec projects runs as well as I predict.

I shorten the valve guide boss a full .200" reguardless.
Vortec heads can have as little lift clearance as .450"
They are not all the same. Measure yours and machine accordingly. .060" extra clearance at full max lift should be considered a minium. More is better.
Your valves, the valve job, your retainers and locks will not be exactly the same as everyone elses. measure your stuff on your heads and set them up according to your specs.

sorry to dig up and old thread, but crane, and sallee chevrolet claim that the 10309 kit is a direct drop in replacement for the stock vortec springs, so is machining the guides just for the sake of caution, or is the manufactuer not telling the whole truth?

http://www.sallee-chevrolet.com/Cyli...ds/Vortec.html

"Crane Cams valve spring and retainer kit. (drop-in springs with no machine work needed)"

Just dropping in springs doesn't fix the guide clearance problem, or make the guides fit the higher-quality seals.

The reason you have to shorten the guides is so that the bottom of the retainer doesn't smash into the top of the guide at peak lift. You machine their outer diameter so you can use the "positive" seals, especially if you're going to run the Teflon ones.

I have smashed them before that is why I was making sure that I did not repeat the mistake. I cut my guides down .2" which appears to have given plenty of clearance. My engine is assembled and ready to install but I just have too many projects going to actually stick it in. My other big project is 99.5% complete so I will be installing VERY soon.

Hey guys, dumb question but i am curious, If u only have to take off such a slight amount why can't u just use a file and take it down a little?? I mean u wouldn;t be messing anyting up where the valve slides and nothing touches where u woudl be filing so shoudn;t it be ok? I mena even if u don't get them all the same it shouldn't matter should it?? thanks for correcting me guys

Yes, it is possible.

Go take .200" (a little less than ¼") off a valve guide with a file, and come back and tell us how long it took, and how long it will take to do the other 15.

hey man its free lol