Mortorq

GeneralDisorder

iTrader: (1)

Well the general rule is that you can't guarantee any more than 470 from unmodified vortec heads. To be absolutely safe you should probably throw in some of these:

https://www.alexsparts.com/valve-spr...ssure-vsk4h50/

The 110 lb springs ought to handle that cam and this way you are guaranteed 550 lift without modifying the head..... They have these in 120 and 130 lb versions also so you could go with a larger cam even.

You could check the spring rate on the crate engine springs and check for clearance but..... I wouldn't risk it even though the parts dealer claims it's ok. Honestly I doubt it.

GD

Mortorq

cardo0

I believe that's the "baby" Hot Cam with same duration but less lift. The correct LSA would be 112 for that cam. I wish GM offered that cam before my cam change on my LT1. Using it on a stock vortec head is your call - specs look close to limit. You should at least find out what springs you have now and measure your installed height with a calipers.

sofakingdom

iTrader: (1)

The cam looks like a decent enough match to Vortec heads.

For valve springs, rather than Alex, I'd recommend LS6 springs such as from Texas Speed, and Comp 787 retainers w matching hardware.

Mortorq

3rdgenmaro

iTrader: (9)

This.

GeneralDisorder

iTrader: (1)

My cylinder head machinist claims the beehives break frequently. Maybe he's not using the right one's.

Do the LS6 springs come with installed height information or do you have to measure seat pressure, etc?

GD

sofakingdom

iTrader: (1)

Stock height on LS motors is 1.80". They can install at 1.75", they just gain about 15 lbs at all heights that way. That would end up at around 130 on the seat and 300 at .470"; a good setting.

The thing about beehives breaking sounds like bull plop to me. Haven't heard of too many spring problems on LS motors myself... Given that most V8 GM trucks have had them since 1999, we'd know about it if that was true.

Mortorq

GeneralDisorder

iTrader: (1)

Well a-lot of people looking for a tight LSA are also looking for big lift and duration. Generally those all go together. Do those heads come with screw-in studs? If not it would probably be unwise to do higher lift and drop-in springs.

108 will have a fairly rowdy idle.

GD

Mortorq

dmccain

iTrader: (2)

Herbert cams has some grinds with lower lift and the duration you are looking at. We've run Herbert cams in several builds including a couple with stock Vortec heads with stock springs.

GeneralDisorder

iTrader: (1)

Ok I'm considering using the LS6 springs. Chevrolet Performance says they're 90 lb seat pressure @ 1.800" ..... adding 0.050" shims to get to 1.750 would add 15 lbs so give me 105 lb?

The Comp cam I'm using recommended 130 lb standard springs. But then I read that with the beehive springs one of the benefits is you don't need as much spring pressure.

So is 105 adequate for a beehive spring when used with a cam that wants 130 lb standard springs?

GD

sofakingdom

iTrader: (1)

Pretty sure those springs have higher pressure than that. Also pretty sure NO GM springs that ever came on Vortec heads will give you 130 on the seat. Also not sure that that's what GM even says themselves that it should have. Frankly I'd be surprised if ANY springs that come on ANY OTC SBC motor have more than 100 lbs on the seat. Which IMO isn't enough for a stock cam, let alone anything that could be called "performance".

In any case, check out the specs on a stock LS6 cam, and the HP #s and RPM range and whatnot that the LS6 is capable of, and draw your own conclusions.

You could spend more and go with something like PAC 1215 or 1218 if you wanted to. Nothing wrong with that either. They're AHELLUVALOT more spring, which is a good thing; it's kinda hard to have "too much" spring, within reason. Basically ANY spring that will install on ANY stock SBC heads without machine work, is IMPOSSIBLE to be "too much".

Vortec heads don't benefit from lift. Reason being, the valve opening, isn't ... The Bottleneck. Once you get to a certain point, the flow stops increasing. Which is NOT to say that just because a cam's "peak" lift is beyond that point, it's no good or whatever; the flow DOES increase during all the REST OF the valve cycle, where it's only partway open; just, going for broke on lift, isn't the way to use those heads most effectively.

They have all this PHENOMENAL intake flow, as a result of moving the port up about 3/8"; but they have the same SUX exh port as any other SBC head. Which, without MAJOR port overhaul, doesn't respond to lift, but rather, to DURATION. Remember: there's 2 ways to get more "stuff" through a valve; either open it more, or open it longer. Since in an engine you can't get more "stuff" (air/fuel" INTO the cyl unless you get the spent (exh gas) OUT, the thing to watch for with Vortec heads is, that they "crutch" the exh side sufficiently to allow the int side to functionate.

A cam on 108° LSA will be very "peaky". That is, tight lobe centers tend to move the peak HP RPM down, and the peak torque HP up; that is, the 2 peaks are relatively close to the same RPM, meaning, the engine MUST be constrained to run within THAT PARTICULAR RPM RANGE to go the fastest. You would accomplish that with gears and/or converter. Wider LSA tends to "smear" the curves out; particularly, it tends to move the HP peak RPM higher, while lowering the absolute peak HP #. Area under the curve will stay about the same, but with the wider LSA, the band over which that occurs, is wider. IOW for a street motor, esp w/o specialized converter and/or LOTS of gear and/or a close-ratio trans w LOTS of gears, the wider LSA will give more "fun factor" on the street, although not as low ET in the 1320'.

Whether that particular cam is "best" for your build depends therefore on MANY factors. Are you going to be racing YOUR dyno against some other dyno? Pure strip? Sat night parking lot king? Stoplight Honduh killer? Fun on the freeway? Each different application might call for a different cam choice. What is the car going to be used for, what converter & gears are in it, how much does it weigh, how much "big cam" hassle (fuel economy, cold start behavior, bumper-to-bumper manners, emissions compliance, etc.), apart from "max HP", are in play in your proposed build?

GeneralDisorder

iTrader: (1)

Yeah I gave the exhaust side crutches. 1.60 exhaust valves, and split duration 276/288 cam.

Looking at the specs on the LS6, these will handle it's .550 lift installed @ 1.80 so I should be just fine with my .500/.520 cam.

Apparently they are 90 lbs seat pressure. But the physics of the beehive design mean this works because the harmonics that would bounce a standard spring back off its seat without heavy seat pressure don't exist in the first place and the top of the spring/retainer is lighter meaning less force required to close it.

Super deal for beehives. $68 from summit wholesale (Atech)

GD

Fast355

iTrader: (2)

The Assembly manual on the engine with the 151' cam installed shows that Scoggin Dickeys is wrong. The assembly manual and my degree wheel both agree. 151 cam IS on a 108 LSA and a 109 ICL the way it dropped in my L31 with a GMPP Single roller chain.

Mortorq

sofakingdom

iTrader: (1)

GM doesn't supply a cam card, because they don't have to.

Would you do extra work if you didn't know for some reason that it was required?

Neither would they.

After all, they're :notworthy: GM :notworthy: They're not "competing" with abuncha :mryuck: aftermarket :mryuck: ... organic fertilizer. They make the rules. Everybody else follows. (or doesn't...)

They put themselves on a pedestal above everybody else. Doesn't seem to bother them that their parts don't win races. Good parts and all, sometimes; but that arrogant, self-important, smug, condescending attitude, is one of the reasons that instead of being 1-2-3 in the WORLD, with everybody else a FAR DISTANT non-competitor, they're now ... much lower. Humbled, as it were. Yet they still retain some of their haughty arrogance. Their day will come.

Fast355

iTrader: (2)

I was running the cam in a 350 Vortec with 906 heads with 2.02/1.60 valves, LS6 springs, Comp 787 retainers and 1.6 roller rockers. Idle vacuum was about 18 in/hg @ 750 rpm in Park/Neutral. Deduct about 1 in/hg in Drive.

This was a warm restart playing around with open cutouts one day. Just giving it moderate blips on the throttle trying to reproduce a lean spot in the acceleration fuel. My 5.7 has 24x coil per cylinder and DBW on it. If I only had a dollar for everytime I heard DBW has crappy throttle response LOL.



Not sure why Scoggin Dickeys did not provide Summit Racing with accurate information. 109 ICL and 107 ECL provide a 108 LSA.​​​​​​

Mortorq

Mortorq

Fast355

iTrader: (2)

No but I have run several cams with in stock vortecs with and without 1.6s. My stock 062s ran fine with a LT4 cam and 1.6s and later a 4x4 Xtreme grind. 2.02/1.60s open up the flow by a fair amount compared to 1.94/1.50s especially at lower lifts by providing increased curtain area.

GeneralDisorder

iTrader: (1)

The general consensus is that opening up the exhaust valve and increasing the exhaust duration (split duration) helps the Vortec heads. Pretty much all conversations I have seen agree on this - that the exhaust flow is weak so it needs "crutches" like the larger exhaust duration. There is much less agreement on the intake valve size but from a logical perspective - the intake valve is at the end of the port so the port is still going to act much the same it's just going to move more air at lower lift as the effective cross sectional area of the end of the port gets larger faster due to the larger valve. Although most say it's really not necessary as the intake flows well enough already. My head machinist only put in 1.6 exhausts and left the intake stock.

GD

arrg

Just a data point for you: I just installed a set of LS6 springs on a brand new set of 906 heads last week. With the 787 retainers and stock locks, they all installed @ 1.76-1.77" with no shims

GeneralDisorder

iTrader: (1)

Interesting. I just installed mine on 062's (99 heads) and they needed .030" shims to get 1.76" I did use a height micrometer for checking.

I checked the seat pressure and they were still reading around 90 lbs. I read that beehive springs don't need as much seat pressure as conventional springs to control bounce, etc. My cam called for 130 lb seat pressure with conventional springs but my cam profile is smaller than an LS6.....

GD

skinny z

Test results via Comp/Vizard: The 26918 vs the 987 with 5% less on the seat, 17% over the nose and 1000 RPM more before loss of valve control (5.750 vs 6,700 RPM). Valve lift .544".
On a personal level, I've used the 26918 with various cams. .530" -.570 net lift (via 1.6 ratio rocker) and 6500-7000 RPM. One custom grind with XFI lobes as well as Comp's XR276HR and XR288HR. Out of two sets of springs, only one spring failure and that's with the 288. That spring had only ever been on the 288 and was purchased at a different time than the other set. The later set went tens of thousands of miles and when sold, still tested within spec.
That said, I've taken this latest build to 7000 on the 1-2 shift and have been in excess of 6000 for steady state and think that this is the limit of the 26918 at that lift. Or perhaps more accurately, just beyond the limit.

GeneralDisorder

iTrader: (1)

I'm somewhat concerned that the higher ramp rates of my cam vs. the LS6 stock cam, even though the LS6 has more lift, may require more spring? My Comp cam:

276/288 (224/236), and .502/.520 - calls for 130 lb springs.

LS6 stock ('02+) cam specs:

270/277 (204/218), and .551/.554 - calls for 90 lb springs.

I currently have the LS6 springs installed @ 1.76 and they are still testing around 90-100 lbs.

Do I put in the PAC 1218 springs instead? Or rock it as is?

GD

skinny z

That looks like the XR276HR spec which I ran for years with 26918 springs and 1.6 rr. No issues whatsoever. This was on stock Vortec heads. I required a .050" offset keeper to get away from the 1.7" stock Vortec spring height. Further to that I also ran a custom grind using Comps XFI lobes with 274 adv/224@.050 and .575" lift also with no issue although the later was a little noisy.

GeneralDisorder

iTrader: (1)

The 26918 springs are a 125 lb seat pressure Very similar to the PAC 1218 spring which is a 130 lb seat pressure.

So you think the stock LS6 springs are a no-go at this station? With their 90-100 lb seat pressure?

GD

skinny z

It does seem a little light. Even with a 5% reduction in seat pressure required when comparing the conical spring to a conventional one, that's still 120+ lbs. That said, there appears to be a few here that have had success with the LS6 spring. I'm not able to access my files (using my phone) but I'd like to know how the open pressures compare. You could pull out the shim (if it's still in there) to increase pressures slightly or even go with a -.050" keeper to shorten the installed height provided you're avoiding coil bind.

GeneralDisorder

iTrader: (1)

Most notably - GM put them in the LS6. Which has a 6500 RPM redline. Apparently the earlier LS6's with the yellow springs were known for them breaking. GM changed the springs (to the blue one's).... ostensibly to improve reliability.

The stock LS rocker ratio of 1.7 gives the spring more mechanical advantage over the push rod and lifter versus the SBC 1.5 ratio.... I'm guessing that's why they get away with such light seat pressure on the LS6?

I'm thinking I should probably go with the PAC 1218 springs and give the cam the seat pressure Comp designed it for.

GD

skinny z

FWIW (now that I'm back at my PC), Comp recommends the 26918 for their 292XFI HR13. (Which is the most aggressive profile I came across after a quick search through their catalog.)
Specs: 292 300 242 248 .584 .579 113°. RPM Range: 2200-6200
They also list them for their XR281HR. XFI™ RPM HI-LIFT Hydraulic Roller Camshafts for the GM LS GEN III / IV.
Specs: 281 283 228 230 .571 .573 112°
That should say something as to what they're capable of handling.
I would think that you would be well within the design limits using them and the cam you've spec'd.

GeneralDisorder

iTrader: (1)

Yeah I'm going to order the PAC 1218 springs. I haven't been that impressed with the Comp products and they give me almost no wholesale margin. $195 retail and I get them for $193..... woohoo! PAC gives a reasonable margin - retail $185, my price $153. They will work with the Comp 787 retainers that I used on the LS6 springs and I already have my installed height set to 1.76 with those retainers.

GD

tater

iTrader: (10)

It appears that the Scoggin Dickey modified, high lift, Vortec heads also still has the "Pressed In" rocker arm studs.

1986BANDIT

strange,but to be safe (and because i already own them)im putting screw in studs into my vortecs anyway. i have access to a cnc mill and know how to program so "why not" right.ive got to start making more use of the high end equipment i use every day that sits and does nothing every afternoon and night!!

tater

iTrader: (10)

I wonder if GM has found a better "pressed In" stud retaining technique. They still use the "pressed In" studs on the Scoggin Dickey modified, high lift, Vortec heads.

Drew

iTrader: (58)

Why not call SD and ask? I sure wouldn't go by what is potentially a stock photo. You don't have any way to know if the photo is accurate or if the studs pictured are pressed or threaded into the head. Generally the problem with SBC heads in the modern era isn't so much that the studs will pull out with a gnarly camshaft, it's that there isn't enough room between the valve spring retainer and the valve guide and/or valve seal.

skinny z

That's a good idea (calling SD) exactly for the reasons mentioned. I would think it unusual for a "high performance" head to have a pressed in stud but you never know. That said, in my industry, we have some fairly exotic adhesives for bonding metal to metal or metal to whatever so as suggested perhaps the technology has advanced for fastening the fasteners.

Fast355

iTrader: (2)

The modern vortec studs are usually held in place very well. I onced asked about having mine upgraded by a machine shop. They said it was extremely likely either the stud or the head would break before they could get them out. I ran that engine for over 3 years, shifting at 6,500 rpm with a 0.540" lift and over 300 lbs open spring pressure. Studs never were a problem.

I also had a set that needed a couple of studs replaced. They were converted to screw-in. Out of the 16 studs, 3 broke and required drilling to remove.

1986BANDIT

so,expect to break some of the pressed in studs when extracting them is what you are saying then? darn it.any fool proof methods other than using a spacer block and a nut?

GeneralDisorder

iTrader: (1)

My cylinder head shop converted my Vortec's to screw in studs and had no problem at all (seemingly) removing the studs. They didn't sufficiently chamfer the threaded holes after performing the threading though so my screw-in studs stuck up at all angles and I had to chamfer the threaded holes myself and set the studs in with thread sealant, etc with the heads already on the engine.

GD

GeneralDisorder

iTrader: (1)

Sure - cut them all off flush and EDM the leftover bits out.

GD

skinny z

That would **** me off to no end.

That's an interesting thought.

GeneralDisorder

iTrader: (1)

Oh yeah I was pretty irked about that mess. Especially since it threw off my measurements for pushrod length (imagine if the rocker stud is tilted away from the valve stem) and caused me to call into question the validity of the pushrod length checking geometry tool since it seemed to give different results depending on which stud I slipped it over. Took me a minute to figure out what was going on....

GD

tater

iTrader: (10)

I just called Scoggin Dickey.

Their modified, high lift, Vortec heads, with the spring kit that is good for .525 lift, STILL has the pressed in factory rocker arm studs.

They told me the only set that comes with screw in studs are the heads that are machined for guide plates.

tater

iTrader: (10)

Mortorq, did you ever install this cam using stock Vortec heads?

Mortorq

Tater,
No, I never did. Junior’s tuition & a few other things came up.