BronYrAur

iTrader: (1)

Hey guys, I've got a set of Vortecs I'm setting up to use on my 305 (for now) with a ZZ4 cam. My machinist wants to set them up with larger diameter springs in the ~150# seat pressure range and I believe ~310# open. I will for sure be using screw-in studs, but he also told me not to use self-aligning rockers, I currently still have stockers on there, which he said would break under that pressure. He said I need to go the guide plate/non SA rockers.

What are some of your suggestions on valvetrain/rockers? I'd assume I would have to replace my valve covers also if I go with non SA rockers, since mine are centerbolt and meant for narrow arms. Give me some input guys. He was kind of talking me out of putting work/money into stock vortecs with their fairly thin decks.

Atilla the Fun

Wow, you sure got suckered. Forget the screw-in studs, keep the self-aligning rockers, and use these springs: http://www.competitionproducts.com/H...uctinfo/98111/
That'll give you good power through 5500 rpm.
Vortec decks are NOT so thin as to negate the value of porting. Here's the info on that: https://www.thirdgen.org/forums/engi...c-heads-2.html

BronYrAur

iTrader: (1)

Thanks for the reply. I didn't do any work I left with my heads. The screw-in studs were my choice, because the last set of heads I had yanked 4 of the press-ins out. Those springs you suggest look like they're recommended for a mild flat tappet cam, is that enough for a mild/mid roller cam? Competition products doesn't give much detail on their parts I've noticed in the past.

I guess the deck seemed thin, but compared to other OEM heads I've got it seems pretty standard. Thanks for the link, good info there.

Atilla the Fun

these springs are 90 psi at 1.700", but that's better than the springs that GM puts in the crate ZZ4 engines. These springs will also fit stock retainers, and accept 0.515" lift if installed at 1.700". You do need to check your spring-to-valveseal clearance, and your retainer-to-seal clearance, but otherwise, just pin the stock studs and you're good to go. Keep it to 5800 max.

AlkyIROC

The springs should be close to what the cam recommends having and the springs should be set up to what the cam recommends. High seat and open pressure springs are only recommended on billet cams. If high spring pressure are used on a cast cam, they will break the cam. High spring pressures will require screw in studs. If you have low spring pressure springs pulling out pressed in studs, you may have other issues.

Like Atilla recommends, springs that are similar to what the ZZ4 cam wants will work fine.

The triple springs on my BBC heads have around 300 pounds seat pressure and around 800 pounds open.

Atilla the Fun

All GMPP roller-lifter cams are steel-core, not cast-iron-core, AFAIK

dimented24x7

iTrader: (2)

I would definitely say keep an eye on the RPMs. This is for an LT4 hot cam with LT4 springs + vortecs, but I can say from this that they dont seem to like high RPMs too much with the heavy roller lifters and standard valves (LT4 has hollow stem/sodium filled). https://www.thirdgen.org/forums/diy-...eaks-up-3.html

It looks like the ZZ4 uses LT4 valvesprings. Theyre ~100 on the seat, 260 open for reference.

Atilla the Fun

The 100-pound LT4 springs come in the HOT cam kit, not standard on the ZZ4, unless something has changed Very recently.

dimented24x7

iTrader: (2)

The parts list I saw for the ZZ4 showed them with the LT4 springs. But, it could be wrong.

Never the less, I still think they would be a good reference point for spring choice. Unlike a flat tappet, the roller lifters give a little more leeway, so a little extra spring pressure (within reason) would be nice added insurance.

BronYrAur

iTrader: (1)

Thanks for all the info guys, you've given me a lot to think on and research lately. Lots of good links too.

My thoughts now are Comp 918 springs and I believe 787 retainers. Some other retainers just list valve stems as "stock" so I'm afriad those are for GenIII stuff with 8mm stems. The 787s look like they're set up for GenI 11/32" valves.

My heads are already cut and I have 1.60" exhaust valves. I am going to get all the valves back-cut and possibly a valve job depending on how they check out. My understanding is that the 918 springs with 787 retainers will clear the stock valve guide bosses without machining. I've also seen information in multiple places that these springs set up at 1.800" installed height will give me ~.550" valve lift clearance. So my .510" exhaust lift with the ZZ4 cam should be ok.

Would you guys agree that my information is correct? Also, I will definitely be checking that valve lift is ok once they are set up.

Atilla, that is a very detailed head porting link, great information, thank you. I've read through that thread and I read a David Vizard book about a year ago, so I think I'm going to try my hand at some port work.

dimented24x7

iTrader: (2)

I assume you mean the 26918 beehive? Yes, they will clear the stock bosses w/o issue.

Those retainers will work provided you get the right locks. You might also consider running superlock retainers (747?) and 10 degree super locks. They're stronger and are about the same price. I dont recall what offset you will need to use. Make sure you measure it. You may find that you will need to use offset locks and/or shims to get close to the desired install height.

Atilla the Fun

How do you propose to get 1.800" installed height? Don't even think of using valves that are 0.100" longer than stock. Those really mess with the valvetrain geometry of stock heads.
I suggest you use "plus fifty" locks, and install the 26915 springs at 1.750". This will be safe with your 0.510" exhaust lift. For what you're doing, the 918s are no advantage over the 915s, just a few dollars price difference.
Also, forget Vizard's advice on grinding away the quench pad by the spark plug. It doesn't hurt anything, and removing it hurts combustion. If you want to use your polishing rolls to round off the edges, that's fine.

BronYrAur

iTrader: (1)

Thanks Dimented and Atilla, you guys are a lot of help.

I'm figuring out this valvetrain stuff now. So, straight up no shimming, no offsets, a stock valve length will put you at 1.700" installed height? All these beehive springs reference seat pressure at a 1.800" installed height, is that because they were designed for a LS style setup, are LS valves .1" longer than standard SBC valves? This is just for my education here.

Why do you recommend the 915 springs over the 918 springs. I believe the dimensions of them are the same, just different spring pressures. So do you suggest going for a spring that will sufficiently control the action of the valvetrain with the least amount of spring pressure?

Thanks for the tip on the quench pad, I think I may just stick to a little port work and maybe polish the chambers. I have noticed the throat of the exhaust ports looks very small now after its been opened up for a 1.6" exhaust valve.

Atilla the Fun

The length of LS valves is irrelevant, but LS springs do install at 1.80". And these 915s and 918s allow 0.600" at 1.8", so at 1.75", they'll take 0.550".
Over-springing hydraulic lifters causes them to collapse somewhat. Not permanently, but even so, it's to be avoided. That's why AFR invented their Hydra-Rev kit. You don't need it, the ZZ4 cam is done at 5800 rpm.
As to the exhaust throat, I covered that in my porting thread i linked you to. first make sure they did the 75-degree cut pretty close to my spec, If not, get it done. Then do your best to hand-grind a 90 degree angle on the short turn side, then blend that to create a large, gentle, smooth radius.
On the long side, after the bowl hog, there's no need or place for a 90*, so just blend. Post pics of your first one, before trying the other 7.

dimented24x7

iTrader: (2)

The 915's have a lower spring rate. I currently have them in my engine. They will have around 120 on the seat, and around 280 over the nose. They got my flat tappet cam up to 6k without issue, so they should probably be OK for use up to 5500 RPM on your setup. Just dont go crazy with it and you should be alright. FWIW, a hydrolic roller lifter is about 70% heavier than a flat tappet one, so that has an effect on when float sets in.

I would recommend buying the retainers and locks first to see where your installed height will be.

I also recall my vortecs coming with exhaust valves that had a spun welded hardened valve face that caused the retainer to move down about .050". This also required that the spring seat be lower on the exhaust side than the intake on my factory vortecs. But, the valveguide boss is at the same height as the intake. I seem to recall this limiting the max lift to .480" with the +.050" offset valvelocks. I dont know if this is true for ALL vortec heads. You may want to check it as you may find that you will have to machine the bosses down for standard aftermarket positive seals.

You can check by taking a look at the exhaust valves that came with the heads. If they have the different colored spun welded valve face, then you may need additional machining.

dimented24x7

iTrader: (2)

Thats a good point. That portion of the head is part of the chamber that helps promote the formation of eddies on each side of the cylinder that improve combustion.

Also keep in mind that you dont need to hog the ports out. With vortecs, its more of a smoothing and radiusing operation to get a clean, smooth good flowing port. I ported mine, but never got around to trying them.

Atilla the Fun

But only with that much of it.
Comp lists the 915 as having the same rate as the 918, and both have lower rate than the 26981s. Do the math yourself, you'll see it's true.
What pressure they have on the seat depends on the installed height. I've had 915s to 7000 with hydraulic roller and 2.02" valves, so no problems there.
There's a lot of conflicting info about how much lift stock Vortecs will take, but I've seen them be good for 0.520" out of the box with just a change of springs and locks. So there's been a lot of manufacturing variance.
To cut the guides, the tool that reduces the O,D. is $50, but for $4 less, you can get a tool that does the same job plus cuts the spring seats to accept 1.440" springs, allowing you to run COMP 982-16 springs inverted, saving you over $100 versus running beehives.
Then to cut the guides the other way, for more lift, can be done using a 5/8" bit in any drill. Not ideal, but not a problem.

Atilla the Fun

The cutter is here: http://www.competitionproducts.com/S...ductinfo/4718/
but you also need this: http://www.competitionproducts.com/V...ductinfo/4732/

dimented24x7

iTrader: (2)

As far as the springs go, its the other way around, the 26918 is the highest of them in terms of spring rate, but yes, I understand what your saying. The 915 installed at 1.750 will give the same relative pressures as the 981's at 1.700, which is why I picked them up for my combo.

I agree that theres a lot of different vortec configurations out there. I know mine actually had an absolute max lift of .450". With the flat tappet I originally had, I was actually the hitting the seals with the retainers.

dimented24x7

iTrader: (2)

What cam was that? Im currently converting over to a roller, and am curious myself.

As for the 982, I thought of doing that as well since my heads accept a 1.460" spring, but I already had a set of beehives on hand, so I just ran them instead even though theyre smaller than the cups.

Atilla the Fun

Just to prove the point, I went to COMP's website, and looked up the specs. To my horror, they've changed the specs on the 918s. The old specs were 130#@1.800", 318#@1.200". That gave a rate of 313 pounds per inch. The 915s are also 313, while the 981s are 347.
Rate is different from open pressure. To determine rate, subtract the seat pressure from the open pressure, call that P. Subtract the open height from the seat height, call that H. P divided by H is rate.
The new 918s have NO place in SBC builds. WAY too much open pressure. they will pull studs out of Vortec heads.

Atilla the Fun

I've never seen any problem from running undersize springs, but for anyone concerned, there are seats available that address this, though they do reduce the installed height.
The cam was a custom grind, as are most of the cams I try. That one used COMP's 3112 lobe, a 112 spread, a real ZZ3 block, an L99 crank and rods with ARP bolts, old AFR 190 heads, and an Edelbrock single plane, with 1.75" primaries. I'd be happy to spec you a couple of choices, in a regular thread or by PM.

BronYrAur

iTrader: (1)

Ok, I actually found similar valve springs, the PAC 1218 beehives, for $120, which also have a 313lb/in spring rate and 130# at 1.800 installed height and 318# at 1.200" open.

So, if I get .05 offset locks and Comp 795 retainers (10 degree parts) and install them at 1.750" I should be at 145.66# seat pressure and about 294# and 305.5# at full lift of the ZZ4 cam on the intake and exhause side respectively.

I measured my valve guides to be 0.8" from the seat to the top of the boss. This, added with the depth of the retainer being ~0.35" would leave a theoretical .60" clearance between bottom of retainer to top of guide boss. With the valve seal added on, I'm assuming I should be fine clearance-wise for my cam and still okay if I set up to a cam with more lift.

I also measured the base of the boss' diameter to be Max (out of 16) 0.855" which should be fine for the inner diameter of any of these springs. The top stepped-in portion of the boss gave me a Max 0.52" diameter.

Obviously this is all theoretical until I get everything put in, but it makes me a little more comfortable to start making some part purchases.

Atilla the Fun

You still don't need 10-degree locks, since you're still under 306 pounds. Otherwise, it all makes good sense.

BronYrAur

iTrader: (1)

Well, I figure this is still a budget build and I'll have them later then if I want to step up to a more aggressive cam profile.

dimented24x7

iTrader: (2)

I wouldnt be surprised if the PAC springs came from the same vendor as teh comp ones. A lot of teh parts now sold by various cam companies all come from the same manufacturers. Those springs are virtually identical in specs to the comps.

I also used the 10 degree locks/retainers as I have several sets of single and dual coil springs that Ive used over the years, some with more open pressure than others. The cost difference isnt huge, so it cant hurt to get something a little extra.

BronYrAur

iTrader: (1)

From what I've read, it looks like the old Comp 918s were supplied by PAC and then they changed suppliers a few years back, which seemed to coincide with problems with their springs. Not sure who the new supplier is, but general consensus seems to be that the PAC springs are very good.