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Discussion in 'Engine Topic' started by MikeM79, Jul 4, 2006.
Hey Dirt, are flow numbers posted somewhere in the guide for stock or ported vortec heads??
Not sure if they are or are not. Lot of info posted there, kinda tough to keep track of it all right off the top of my head. Guess you'll have to search through.
New to the forum, great thread.
Got a couple of vortec topics I didn't see kicked around so I thought I would stir the pot. This thread needs to live.
1. The RamJet crate engine runs what appear to be bone stock vortec heads (12558060), the 14097395 cam, and 1.6 roller rockers which puts intake at .460 and exhaust at .481 according to their literature. I've never seen any mention of GM altering these heads to run .481.
Putting together the same setup and scratching my head at "you need to check anything over .460" posted here and elsewhere. I've been up and down the RJ service parts lists and don't see any mention of "trick" parts to make this setup work with off-the shelf assemblies.
Are there different max-lift ratings for intake and exhaust? I'm looking at my fresh set of 062s and I will say the valve seals for intake and exhaust are different colors. Exhaust seal is orange and intake is black. I can't detect a difference in height, but I don't know that I could perceive .020" peering through coiled springs at an angle.
Is .481 safe to run on the exhaust without checking? It appears GM thinks so...
2. Really like the "getto grind" option, do you grind 3/16" or 3/32" (both figures are listed in this thread, I'm guessing 3/16" is way too much). Any downsides? Weaken the retainer? Any benefit to polishing the grind?
3. Saw the Comp beehive springs mentioned early in this thread to gain lift, but were quickly dismissed as too expensive - look to Z28 springs. I've been thinking about using the factory yellow beehive springs that came on the LS6. SDPC has them for $52.25, might be able to bag some on e-Bay cheaper.
Then buy the Comp 787-16 retainers for another $50 to get them to work with vortec diameter valves. I've seen it mentioned that you can reuse your existing keepers with the 787-16s, or pick up the Comp 7 degree keepers for around $30. Any thoughts on using the stock keepers with the 787-16 retainers?
Now we're at $100 or $130 to get .550 and the question becomes: Are these LS6 beehive springs quite a bit better than the springs that came on the vortecs or the Z28 spring alternative? There's a lot of buzz surrounding the beehive design and I'm curious how much is hype and how much is substance (pun intended). I may try a higher lift cam down the road so the .550 upward mobility has its appeal.
If you drop these springs into stock vortecs, is the installed height in the range of where these springs were designed to run? SDPC lists the following specs, but I've seen different numbers posted here and there.
Installed Height: email@example.com
Open Pressure: firstname.lastname@example.org
Max Lift: 0.550"
What are the stock vortec intalled height and spring pressures again? Does this seem like a good path to explore with a roller cam? What do you think about the spring pressures on these compared to some of the other high-lift/no-machining options available for vortec heads?
4. Really liked the "how to" on pulling out the press in studs and tapping for screw-ins. I've been a bit worried about tapping the studs straight so they do not affect valvetrain geometry. I'm not looking to grind up my new self-aligning Pro Magnum rockers on "out-of-whack" studs because I'm not a good machinist. I understand the Proform tool helps guide the tap but I still have my concerns.
I've been leaning towards installing 1/8" roll pins through the stud boss and stock studs. The Mr. Gasket 806G rocker stud pin kit comes with a 5/32" drill bit and pins, but that seems a bit large for 3/8" studs to me.
Been looking at some 1/8" x 7/8" heavy-duty steel coiled style spring pins from McMaster-Carr. Part Number: 95755A236 $10.45 per Pack of 100. With a double shear strength of 2,000 lbs. I think I can get away with 1/8" without unnecessarily weaking the stud boss or stud with a 5/32" hole. Any thoughts on the "pin the studs" approach vs. "tapping for shoulderless screw-in studs" - pros and cons?
Yeah, I'm running a mild cam for now, new springs and fastening the studs might be overkill, but I would rather monkey with these heads now, while they're on the bench. If I can do it on the cheap, all the better. Who knows what kind of bumpstick I might throw at 'em later.
Knowledge is the key to horsepower on a budget and this thread delivers. I've been looking into vortec heads for a few months and just came across this thread today. Nice work. Hope this barrage of questions breathes some new life into perhaps THE best vortec thread on the net.
Thanks for your comments. The whole idea when this thread was first put together was to help the guy who wants to use Vortecs but is not sure what they are all about. The board admin have been gracious enough to make this topic a sticky and keep it around for the long haul, of which we are all appreciative.
On to the topic at hand. The situation with the allowable valve lift -- GM's info changes periodically on this, for example from .460" to .475" in the new 2007 GMPP catalogue. The reason for this is it appears there is enough variation to allow safely in the .460"-.480" range. .460" *should* be safe. Yes the Ram Jet has .460" intake and .481" exhaust with the 1.6 rockers, so I guess from that we can infer GM thinks .480" is okay.
If you can use a stock diameter 1.25" single-wound spring, the stock retainer is what I would use. The reason is because it is of a high-strength light-weight alloy design. The "ghetto grind" -- 3/32" is the correct figure. I'm bad with the figures on this and have made the mistake of stating 3/16" on more than one occasion for which I apologize. That is indeed too much. The 3/32" is an approximation and is about what I took off on mine. Worked just fine with a .488"/.510" Crane hyd FT cam, and when they were removed and inspected after about a year or so, they looked as good as the day they first went on.
Beehives are the best springs. I didn't go that route because I didn't need them for what I was doing. From what I can see by your post you are looking at the cheapest way to get into Beehives on the stock Vortecs -- '02-'04 LS6 beehive spring, 787-16 retainers and stock locks. That should work fine, I'd check retainer to guide clearance anyhow just see how things look for certain. Just my opinion on this, but unless the Vortecs in question are really well ported, I don't see the benefit to .550" springs when they max-out flow-wise at just over .500" lift. In the old Car Craft "Cheap Street" class, the rules were limiting the valve lift to .485" flat-tappet cams and the fastest cars were using unported Vortec heads.
What is the installed height and spring pressures for factory vortecs?
Do you have any thoughts on "pin the studs" vs. "tap for shoulderless screw in studs" (pros and cons)?
Vortec Heads The Definitive Guide
Hey, i am looking for some info on how big of a carb you can run with the Vortec heads... Right now i have a 600 V\S Holley i am going after a 750 DP will this be to much carb for me?...
I am going to leave the carb all stock jettings and squirters stock also... To help you out more i will give a run down on what is in my car now...
350 4 bolt main standard bore, vortec heads ported and polished 268 extreme cam 477\480 lift weiand action plus intake manifold 2800 stall tc 10 bolt posi with 373"s like i mentioned earlier 600 holley v\s ....
I am going to try it i think i am after reading tests done with same combo as i have and they used a 750 dp with no problems...
Stock Vortec springs:
PN 10212811 1.25" diameter
80# @ 1.70"
Solid height: 1.20"
Rate: 256 lbs/in.
GMPP says you can pin the studs. If you run machine the heads for screw-in studs you will need to run guideplates. Up to you which method you want to use, they both work.
FWIW, my heads have pinned studs and it makes me nervous. It can't add to the strength of the stud at that point and could make it more prone to breaking. If I had the choice, I would definitely tap the heads for shoulderless screw in studs (for use without guide-plates). These are screw-in studs without the "hex" part of it and I've used these on every head I've machined (except my own, of course ) and you don't have to machine the head for guide plates. You need to use the stock-style self-aligning rockers, though.
If you want to tap the heads yourself, I posted a write-up on one of the first few pages of this thread that shows you how I like to do it.
some one please recommend me a solid cam, matched for non ported vortecs, unported performer rpm intake, 750cfm carb, 3000 stall, and a 100-or 150 shot,
please tell me what gears ill need to. thanks
Why do you think you need a solid cam?