sbcvortec

Hi all,
Currently building a 355 2 bolt main cast crank stock rods etc.(wont rev past 6000)
ported vortec heads,
3 angle valve job
New valves
screw-in studs
PRW Roller tip rockers
10:1 CR with 0.035'' Quench
Air gap intake, headers etc.

Cam Specs:
Howard's Cam CL110885-08
0.525/0.525 lift
278/278 adv dur
225/225 dur @0.050''
108 LSA

I called Howards and they recommend the howards springs single coil (Not beehive) :
120# seat pressure
350# Open pressure

When I started my build plan I chose the LS6 spring because they were used in GM performance application. But when I checked what the cams need and what the ls6 spring offers they do not match.

LS6 spring
90# seat
295# open pressure

I've seen guys run the ls6 spring with the GM LT4 Hotcam... that cam specs are: .492'' lift and 218/228 dur @ 0.050''

Are beehive springs that much better at controling the valve with less pressure?
I don't want to use the howards spring because they wont fit over the valve guide boss.

Summit SUM-174004 130# closed 320# open
LS6 95# closed 295# open
comp cams 26918-16 120# closed 367# open

I would like your opinion on seat pressure vs beehive etc.

Thanks for your time!

Orr89RocZ

iTrader: (20)

in short, yes

i like beehives in stuff like this.

a single 120/350 seems a touch light to me but can support to 6000. I feel that cam will like touch more rpm tho. I like 135/375 and small diameter double springs for milder hyd rollers, or the beehives with similar specs to the comp 26918

sbcvortec

Thank you for your reply! Howards tech and the web site says that cam will work from 2000 to 5800 with only a 2500 stall. I'm guessing the tight LSA has a narrower power band. But we'll have to see, it's ordered anyways.

Any more opinion/ experience welcome!

Orr89RocZ

iTrader: (20)

Yeah the tighter lsa and advanced center line will shorten the power band some but it depends how well ported the heads are. Rpm air gap intake? I feel like it should peak nearer 5800-6000 and hold some power to 6200 shifts

sbcvortec

Heads we're ported as per D. Vizards recommandation (Port Bias and 90% throat opening) Except the combustion chambre... Only did a valve deshrouding. The only reason I went with the air gap (Not ordered yet) was for underhood temps. The other option is a idle-5500 intake which I feel limited.

sofakingdom

iTrader: (1)

Pac 1218

NoEmissions84TA

iTrader: (1)

Finish it Sofa.... Order from....
It's a great recommendation.

sbcvortec

Hi and thanks!

They look very similar to the summit brand spring. But they don't match the recommended spring pressure for the howards cam...

Is there something I'm missing?
Is it ok/safe to run a less open pressure then recommended? I would not like to have the valvetrain to float.
Is my rev range acceptable to run less pressure?
The Comp springs a 50$ US more and I'm within Howards specs. I feel like this would be the smart choice here... I run cheaper parts where I can, but with the cost of 1450$ CND for a cam... I dont want to mess up anything.

Feel free to correct me!

Thank you!
Nick

sofakingdom

iTrader: (1)

TSP or ws6store usually have the best price.

Those springs, or any LSx single beehives for that matter, require the Comp "adapter" retainers part # 787.

It is NEVER "safe" to run less seat pressure than recommended. In fact it's ALMOST IMPOSSIBLE to run "too much" seat pressure, within reason. This is because "valve float" consists of the valve bouncing off the seat when it's supposed to be closing, which is HIGHLY DESTRUCTIVE to every part in the system. People get this idea that "valve float" means the valve gets flung off into space as the lift goes through the peak; this is NOT usually the case. Open pressure is far less critical; you need "plenty" there, but not "too much" as well. "Too much" consists of forces tending to bend push rods and other nice things like that.

That's not an ideal cam for Vortec heads. "Vortec" originally was GM marketing-speak for "we moved the intake ports up about a half inch", and those heads, as a result, have all this MASSIVE intake port flow; but they have the same sucky exhaust ports as any other GM head. Consequently they benefit even more than others from having higher duration on the exhaust side, to "crutch" the weeeeek exh port flow up to somewhat matching the FANTASTIC int port flow. Duration, not so much the lift; in fact adding lift like most asymmetrical cams do, has virtually no benefit at all on stock heads, but is just a side effect of using a "larger" lobe in the same design series, the way that the Comp XE or Lunati Voodoo series do. Typically they want about 8 - 10° more duration on the exh side than the int with about the same max lift. I would urge you to reconsider.

Orr89RocZ

iTrader: (20)

Pc 1218 and the summit listed are basically the same spring. Summit doesn’t make springs, so it potentially could be a pac spring rebranded or maybe someone else like associated or psi. Idk whos making beehives these days. The specs are the same tho

and back to the beehive vs conventional spring. Yes you can use less pressure with beehive and maintain control. Howards recommended loads depend on a lot of variables they need to define, such as spring mass, frequency, valve mass, pushrod diameter and rocker arm type and mass. It possible they assumed a typical mass of a sbc valve and typical rocker arms used. They came up with 120/350 considering that spring type and mass. Different springs may come up with different rates. A beehive being a different design is likely a lighter spring of a different frequency and thus behaves differently and may need less pressure overall. A spring has to control that valve and rocker tip mass as well as some mass of its self. Beehives do it well. In short it will work fine.

sbcvortec

Wow! awesome reply!

For a while I was considering a lunati cam but I could not find a smallish cam with a 108 LSA. From what I've seen, tighter LSA always make stronger torque curves, So that was my primary factor for a cam. I did not want to much duration. The vortec exhaust port should flow around 170-180 cfm at 0.500'' lift. Which is pretty close the some aluminium heads available out there.

For the springs, the PAC 1218 have 130# seat pressure vs 120# for the comp 26918. So this should be ''better'' to prevent valve bouncing off the seat and the open.
But the open pressure is around 45# less for the PAC 1218 vs Comp...

So would you guys run the Comp or the Pac and why?

Once again, Thank you very much for your time. This is my first build and I'm experiencing with the combination I've choosen. I trust DV (I know he's super theorical) and want to try his science.

Orr89RocZ

iTrader: (20)

They both will do the job. Check the install height, both are advertised around 1.800” height, if you are less than that seat pressure will be more. Comp i seen advertised as 125 seat so its not that much different but that is plenty of pressure

sbcvortec

With the 0.050'' offset locks and 787 retainers, I'll be at 1.800'' Installed height... Just have to check rockers/retainer clearance. Push rod geometry will be measured and the correct length will be ordered.

I think I'm leaning towards the PAC spring to have less open pressure (less wear) but if ever I go 383 in the future, the stronger springs might be helpfull with a bigger cam.

Haha sh*t I hate making decisions like this.

Feel free anyone to chime in!

Thanks guy for your time! I know you must get a lot of noobs in here.

P.S. I'm a high school shop teacher. I teach welding, machining and engines. I have a lot of knowledge but not a lot of experience. So your expertise here is really helping. And I'm using this forum as an exemple to the kids to show them how helpful they are and how important it is to match engine combination.

Cheers,

Nick

sbcvortec

Thank you! I missed your reply!

sofakingdom

iTrader: (1)

To Orr's point about how spring "recommendations" are created: one of the cam mfr's main "spec" concerns is, the expected mass of the portion of the valve train on the valve side of the rocker pivot; which includes of course that part of the rocker, the mass of the spring itself integrated from the part that doesn't move (the spring seat) up to the part that moves the most (the retainer end), and that of the retainer. It is often argued that the retainer is the single most critical piece of mass in the entire valve train in this respect other than the valve itself.

The Comp 787 adapter weighs only something around half of a typical steel 1.25" spring retainer such as would be used with the springs Howards built the recommendation around; and of course the part of the beehive spring that's moving, is the small part, which also weighs less than a straight 1.25" spring. Altogether a FAR BETTER recipe for improved valve train stability compared to the straight spring.

sbcvortec

That makes so much sense! I will go with the Pac springs.

Thanks again for your time!

89fast5oh

I was running the comp 26918 springs on a sbf way back in 2004. At the time people were telling me they are junk and to use a heavy double/triple spring. I ran them with a xe lobe roller cam with near .600" and never had a problem. I guess I was just ahead of the times, lol.

sbcvortec

Hahaha right on!

sbcvortec

*Update*

Well turns out one of the heads is cracked... it was magnafluxed prior to porting but I guess it was too dirty. Anyways thats down the drain... Sooooo I ordered some Brodix IK180 setup for roller. Price wise was 400 cnd more than the vortec all said and done (intake etc.). I think that cam will like the extra flow. I'll disasemble the heads clean up the bowls a bit and that will be it.