SDPC modifies their vortec heads with bigger springs, and some machine work to accomodate those springs and more lift. SDPC says the heads are good for .525 or .550 lift depending on where you read, but most people seem to say that you can't use push-in studs with that kind of lift.

Right now I've got a mild cam .442/.465 lift hydraulic flat tappet, but I want to upgrade to 1.6 rockers when I install the heads, plus I'd like the option of running a bigger cam later on.

Will these heads survive with the lift that SDPC claims without installing screw-in studs?

 

Is pinning the studs an option?

 

I have no idea. I haven't heard of that.

 

Pinning the studs = drilling through the stud and the boss, and driving a roll pin through it all

Works about 75-80% of the time; the rest of the time, ends up scrapping at least one head out of a pair. For either a broken-off drill bit, or stud bosses that break in half.

They won't get it with anything resembling a modern cam though. With any kind of a real cam, and especially one that would give the engine any kind of RPM capability, that package as it's sold would be inadequate. Pull-out studs won't stand up to very much abuse before they start to ..... pull out.

However, for that ancient lazy thing you've got in there now, they'll be fine; even with the added lift from the higher ratio. Go ahead and run them as they come, you'll be OK. Then whenever on down the road you get around to bringing your cam into the latter half of the 20th century or even newer, get the heads set up for whatever you get.

 

Jesus, my cam isn't carved out of stone by migrant cavemen. Flat tappets are still more popular than rollers, especially if you're unlucky enough to have a pre-87 block that requires an overpriced retrofit. I'll have nearly .500" of lift with the 1.6 rockers, and I'm concerned that I may be pushing it with the press-in studs. The part that I found curious is that SDPC rates these heads for more lift than I'm used to seeing with press-in studs. I didn't know if perhaps the unique parts associated with the vortec heads somehow changed what's typically acceptable for lift with press-in studs.

But in any event, I don't see where this pinning procedure is any easier than just tapping the damned holes and screwing some studs in.

 

You sure?? You watched it being made???

Personally I prefer the ones forged in the fiery furnaces of Hell by 10,000-year-old gnomes, out of pure virgin nonobtanium and irreplacium alloy.

Seriously, those Summit (or Melling or Edelbrock or whoever yours is branded as) cams, are a relic from the 60s. They're REALLY REALLY mild, regardless of the "specs". It's not about flat-tappet, it's about lobe design. They are not anywhere near in the same league as a Comp Xtreme or Lunati Voodoo or Isky Megacam, which were all designed at least since the invention of the calculator - let alone computerized finite element analysis. They were designed in the days before aftermarket head castings, before valve springs of endless variety were cheap and easy to get, and all of us that didn't have sponsor money to spend on our cars just used stock springs and replaced them alot in hopes we'd catch them before they broke. They have real gentle ramps, real easy on springs and stuff, because they HAD TO BE back then; and if they're easy on springs, then they're easy on studs too. Which is not a bad thing, as far as it goes.

 

Jim, what will pull out your studs is spring pressure, having an agressive cam needs more spring, hence the bigger cam will (through the chain of events needing the bigger springs) pull out the studs.

Pinning your studs usually works fine. I found it to be far too much work, those studs are hard as SIN to drill through. It's not "easier" then putting in screw in studs, it's cheaper.

I used mr gasket 1076 (I think), the collarless thread in studs. I made myself a jig to help pull out the old studs, and align a taper tap, to tap it for the studs. the collarless studs don't need you to mill down the guide boss, and use guide plates. I have slots in my heads, so I didn't need guideplates, so these fit the bill perfectly.

Jim, what rockers are on the car now? stamped 1.5 stock ones, or an aftermarket roller tip? or any aftermarket ones? I think if you have aftermarket 1.5's, then you've already spent the $ on them, no point blowing another $100 on new rockers, when you could get a better aggressive cam, and keep using the 1.5's.

my

 

Right now none of it is on the car. I just bought the heads (used), but my intent was to buy some 1.6 self aligning rollers, most likely Comp Magnums.

For what it costs, I could throw a new cam in too. I suppose if I'm going to the extremes of taking the heads off anyway, I might as well just yank the motor and replace the cam too. I'm running one of those fantastic Summit grinds that Sofakingdum is so fond of.

Sofakingdum, what exactly makes the cam so "mild"? Is it literally mis-labeled, or is the ramp profile that important to making power?

 

The ramp rates really are that important.

 

I agree, at least get one that was designed in the 21st century. The three companies mention above have some good flat tappet cams using the latest technology.

 

self aligning rockers, last I checked, were a lot more $ then non. It might be cheaper to run guide plates, then it would be to run SA rockers. But price it out and find out.

you're sticking with the TPI setup? need a computer friendly cam, or can you reprogram the ECM easily? Aftermarket intake? I don't want to recommend a cam without a lot of info, but hey, you never asked for cam suggestions either so ....

Best way to think of that cam: look at the advertised duration, subtract the duration @.050". That gives a good first glance at the ramp rate. That's how fast the lifter starts to move up. On that stellar summit cam, it's something like 272-214 = 58*.
Say on a comparable compxe, the 262 :
262-218 = 44*. So the lifter goes from .004"ish lift to .050" lift faster.

the powerband will be wider, it'll make more power due to larger lift (.462vs..442"), the lower advertised powerband will make it idle better, give better vacuum etc etc....

 

Guide plates would require machine work to the heads, as well as screw in studs. The price difference between SA and non-SA is only like $30 or so I think.

 

Right now I'm running an accel base with SLP runners & SVO injectors. The short block has flat top forged slugs.

The plan will be to put a stealth ram on the car when I do the head swap, so my cam choice will be aimed at that.

Right now I'm running a 165 (MAF) ecm, but since my tuning skills seem to be horribly lacking, I'll probably switch to a speed density system shortly after the parts swap since those seem to be much easier for a novice like me to modify the PROM code for.

How much cam can I use on the Z28 springs and press-in studs that those heads come with? The heads are fully assembled, and I'm not too keen on dis-assembling them just for the screw in studs if I don't have to.

 

You will never see a fair direct A-B dyno test comparing one of the "old relic" designs (summit, melling FM) like the one the poster now has against a "extreme cam" by any manufacturer. Ever. Why? because the power diference is so small, the extra cost and accelarated wear penalty is hardly worth it. Not saying you should not run the "Extreme Voodoo" stuff. Just be aware that these old grinds are still around for one reason. Cause they work very well overall in a street motor (in the real world) for a reasonable price.

Don't get hung up on valve lift. A small block chevy is perfectly happy with .450 to .480" lift. Selectlng the proper duration ( rpm range) is much more relevent.

MW66nova 's car is a perfect example. The cam I recomended is about 25-30 years old and has a net lift of .460"-.480" yet the car runs near 12 flat.
Does your street car run that fast?

If I was after more performance I'd change the cam grind before bothering with 1.6 rockers.

 

Interesting information. That's quite a bit different than what I'm used to seeing. I see various opinion about the old cams, but I generally seem to hear most often that I should get as much lift as I can for a given duration.

What duration do you recommend that I go with to get maximum power without losing street manners? With the HSR/Vortec combo, I'm going to be looking for a nice wide torque curve, and I'm not going to spin the motor above 6k rpm.

It would also be nice if I could see some mid 12 second timeslips out of this motor too.

 

"Street manors" is a relitive term. Just right to one person may well be too racey for another. Need more specific info on your actual combination to give you a specific cam grind. What computer management system will you be using to control the HSR EFI? T5 manual trans? auto? rear gearing e4tc etc.

I'm thinking around 218 to 230 @.050 in a hyd roller (roller block) or nice flat tappet in an older block 3.73:1 gearing sticky tires

 

converting to a roller cam is out of my budget. I'm using a non-roller block.

The short block is a .030 350 with forged TRW flat top slugs, stock crank and rods. Trans is currently a T5, but will someday be a T56. Current rear gears are 3.42, and will stay that way at least until I put in the T56, at which time I may or may not go to 3.73s. Most likely I'll stay with 3.42s until I build a new rear end, but that's way down the line.

Anyway... my current engine management is a MAF setup with the 165 ECM, but I will likely convert to a later speed density system. In either case, I'll be doing my own prom tuning.

I don't mind a somewhat choppy idle, but I need enough vaccum for my brakes to work, and for the car not to stall itself out at anything below 1000 rpm. I'd like a nice broad torque curve that has enough low end to make street driving fun. I don't want to spin the motor past 6k.

What I've had in mind (granted, this changes daily) is something with a duration around 220-225 on the intake, 230-235 on the exhaust, with as much lift as I can get with that duration. I don't want my LSA any narrower than 112 degrees, though I suppose if i'm burning my own PROM, I can try to deal with a 110 if it's absolutely necessary. Because I want this to have a good midrange torque, and because I don't plan to turn the motor past 6k rpm, I want to make sure I don't wind up with too much cam, but I also don't want to short change myself on power.

 

comp 268 computer controlled, 12-268-4
I think would work best for you.

 

I've been quite upset with a lot of the big GM Performance parts distributors modifying Vortecs for more lift but not using screw in studs. The "pull out" studs that someone here used to call them (as if we don't know who that someone is now), are not good for that much lift.

So why not just add another $50 to the price of the "modified for higher lift" heads and call it done??? I don't quite understand why they don't do that.

Another thing that entertains me a lot is mass marketing. Comp Cams has made these "Xtreme Energy" cams for a very long time, and still do. They call them the Magnum series. The only real difference is the "Xtreme Energy" series are dual pattern cams.

E.G.
The Magnum 270 is 110* LSA, 270* Advertised, 224* @ .050", .470" lift.
The Magnum 280 is 110* LSA, 280* Advertised, 230* @ .050", .480" lift.

The Xtreme 268 is 110* LSA, 268* (slightly less than the Magnum 270*)/280* Advertised, 224*/230* @ .050", .477" (slightly more than the Magnum 270*)/.480" lift.

Anyone notice a similarity? Granted, the "Xtreme" series may have a slightly more aggressive accelerated ramp, but how much more? Regardless, it's worked for them. They're selling the crap out of these cams.

Off my soap box...

I'd get a quote from them for screw in studs if I were you.

 

Not an option. I'm buying the heads used. But, since I'm not installing them right away, I'll have time to tear them down and install screw in studs if necessary.

 

Here's a tip for you to consider.
Use the Manley valve springs part #22410 & retainer Part #23652 and Pioneer screw in studs part #850001 without the hex.
They fit the Vortec heads without machining and will allow .520 lift safely.
I have used these numerous times with success.
All you have to do is remove the factory studs and tap the bosses, use a pair of nuts locked on to the stud to screw them in.
Comp makes a stud remover tool part # 5306 that helps to remove the studs and tap the holes (no drilling needed).
HTH

Edit: pressures are 125# seat...340# open @.500 lift

 

The heads already have Z28 springs and LT4 retainers. The SDPC heads are already machined for bigger springs and for standard valve guides, so those springs and retainers should be unnecessary.

 

I recomend this cam a lot cause it's a good street cam.

Crane Cams H-278-2 PN 113801 or 113802 w/ lifters

Specs are 278-290(ADV) 222- 234 @.050" .467" .494" 114LSA
The lift using 1.5 rockers is plenty. Don't let a few thou either way, sway you. The overall cam lobe dynamics are much more important.
This cam is a modern, fast action non-symetrical fast ramp rate cam that is very stable and works well. It is a good step up from what you now have (which is a good overall street cam too) without getting into "extreme Voodoo" witchcraft. If you want to be adventuristic use 1.6 rockers on the intake side but 1.5's are plenty on the exhaust side.

This cam has a wide power band and good manifold vacuum and street manors.
good power to 5700-6000 yet good low end performance. I would not go bigger. Has EFI friendly 114 LSA.
I would "pin" your vortec rocker studs or pull them and tap for Screw in studs. Either method is good.
More than enough to run solid 12 sec ets. Just wrap a good motor around it.

I think you'll find this cam is a good match to your Stealth Ram project.