Just looking for opinions on why a dual valve spring broke on my LS3 setup - bad luck, too aggressive a cam, something else.
Here is my NA setup:
419 ci LS3, brand new block, CNC blueprinted, all forged internals. 9 years old now, about 12,000 miles on it
TrickFlow LS3 255 heads
Texas Speed Stage 3 Cam - 231/246, .640/.615", 111 LSA
Crower Shaft Rockers
Morel 5315 Lifters
COMP 3/8"/.080" pushrods

This setup has worked perfectly for years with many hundred runs up to 7000 or even 7200 RPM.
Shortly after doing some recent tuning (Holley Dominator) and revving fine to 7000, while driving on the highway, the sound changed dramatically and the engine had no power. I limped it home. Removed plugs and compression test showed Zero in cylinder 1.
Removing valve cover showed that both intake valve springs were broken and valve was somewhat stuck in open position. Removing the head revealed that the intake valve was bent; fortunately only tiny scratch in the valve recess of the piston.
All pushrods are perfect as are the lifters. IIRC, I originally adjusted the rockers for 1/2 turn pre-load which might be on the low side.

Since a common reason for spring breakage is coil bind, I was curious how much the TrickFlow heads supported; they claim up to .650 cam lift. I place the head in my hydraulic press, mounted a dial gauge and measured that coil bind occurred at .790" of valve movement, so plenty to support my .640" lift cam.
Overall the damage is minor and plan on only buying new valves, springs and seals from TrickFlow, and replacing all springs. (I moved a good intake valve into the broken position and it sealed perfectly.)
I already have another cam on order from Brian Tooley - their "BTR 400+NA" with specs of 236/25X, .636"/.636", 114 LSA. Yes, I know another aggressive cam/lobes.

Maybe 12,000 miles is all I should expect from a set of spring with such aggressive cams; if true I can live with that.
TrickFlow lists the springs as 160lb closed and 450lb/inch.
Are their suggestions for better springs?
Should I replace the lifters too? Even though they look brand new?
Or do you think there is hidden head damage and I should replace it? (I don't have time for a machine shop to schedule it.)
Or am I missing something?
Thanks.

 

pac makes good springs.
id probably go with psi springs if i wanted an even better one.
not sure what spring trick flow uses in their assembled heads but it would be useful to find out.

 

Actual if you are .150 from coil bind (.790-.640 = .150) that is actually a little too much cushion. I would look for something in the .100 coil bind range. Of course you have had many miles and high rpm on it and stuff can happen.

 

Thank you for the comments so far.
Granted I have never thought about valve springs, much less claim to know anything about them, but I don't understand the comment above about "actually a little too much cushion" as extra cushion sounds longer lasting to me.
Talking to TrickFlow this morning, I learned that they have an optional stiffer set of springs.
The "regular" ones have these specs:
150 lbs at 1.800, installed height
400 lbs at 1.200, open (.600" lift)
370 lbs/inch.
I calculate 385 lbs at .635 lift
Hmmm, they are rated at only .625 max lift.

Their optional ones (by PAC) have these specs:
155 lbs at 1.800, installed height
465 lbs at 1.200 open (.600 lift)
448 lbs/inch.
However, I calculate only 424 lbs at .600 lift and 440 lbs at .635 lift.
They are rated at .650 max lift.

From the recommendation of PAC springs by @TrendSetter above, the higher max lift and the recommendation from the TrickFlow representative, I will order the Optional springs.

NOW the question is: Are my Morel 5315 lifters adequate for 440/465 lbs springs?

Perhaps the GM Performance "Caddie Race Lifters" rated to 8000 RPM would be better; at the RPM they gotta handle stiffer springs. ($535).

Again, all thoughts or suggestions are super welcome.
Thanks all.

 

id have to dig around in some of my old books but the jist of the topic is for a spring to be in ideal conditions, your max lift should be quite close to coil bind. i think its 020-050 range. its been quite some time since i did that sort of combo, so the exact numbers are a little fuzzy for me.

 

See what your actual spring pressures are on your current springs. They could have simply fatigued.

When you measured coil bind, what was the starting valve spring height that you measured from and does that height match your installed height?

 

Darn, after looking up my 9 year old invoices, I discovered that my Trick Flow heads came with the optional stiffer springs, AND I have Morel 5315 Lifters, not LS7.
I already ordered the replacement springs, valve, guides, seals to repair my head.

 

9 years is a long time to have a coil under pressure.

 

Yeah, that's why I'm replacing all the springs.
Reading every more posts on this and other forums, it seems the Morel 5315 are similar to the LS7 lifter rating of 400lbs open spring pressure and 6800 RPM. Since I exceed both, I'm very inclined to go with the GM Performance Racing/GMPP "Caddy" lifters.

Also, reading that the recommended preload on the Morels is .060", I suspect I have much less. My Crower Shaft Rockers are adjustable; I can turn the pushrod when the valve is closed. I will check before I remove the 2nd head.

 

12k Miles is not much, 9 years I suppose even if just sitting.

As concerned as you are and understandably so, about which springs to use next, and you're gonna be using a BTR Cam, why not use the recommended BTR Springs for that BTR cam???

I personally run PSI ML 1516 Single Springs.

 

I perked up at the comment about many 100s of runs 7000+ rpm's. Me thinks just a bit tired.

 

Springs weaken with heat cycles only. Guy on the Chevelle forum has a set of springs clamped closed and stored for 20+ years without any pressure loss.l, or reduction in height. He checks them every few years and reports back on them.

 

I have heard the same thing relating to pistol and rifle magazines loaded vs unloaded....

 

I simply didn't know if BTR springs for stock LS heads would work properly on a TrickFlow head. And they seemed too cheap.
I really like your suggestion of the PSI ML 1516 springs as they are single beehive with a good 450lbs at .650" lift. I always wonder how much friction and heat is produced by dual springs. I see that BTR also sells them; as I plan to order lifters and head gaskets from BTR, I will ask them tomorrow about the PSI springs. So thank you for that!

 

Have you checked the rates of any of the springs that didn't break?

From what I have read over the years, it's actually better for the spring to be setup .060 to coil bind, IIRC it helps with harmonics.

TFS had problems several years ago with their heads. I can't remember if it was a valve or a spring issue that were killing engines.

I remember reading about it and a friend of mine had a problem with them on his racecar, but it's been so long I can't remember exactly what the problem was.

There's a member on this board who works for PAC, I can't remember who it is though.

I bought a set of TFS As Cast 220 heads last year and had questions if the springs that came on it where good enough for my application and he helped me out.

 

Thanks for chiming in @LilJayV10 .
I installed the TFS heads in 2015, which I think is shortly after they became available. Maybe they had troublesome springs then. Perhaps their replacements are better.

In any case, my higher priority now is selecting the correct lifters before the heads are reinstalled. Springs can be changed relatively easily later. I don't want link lifters because I change cams every few years if not sooner. I experiment a lot. I even have the Edelbrock 2-piece timing cover so that I don't have to remove the balancer and entire cover to swap cams.

 

The spring cares about installed height and coil bind. It does not care about the cylinder head's brand.

 

Thanks again for the many additional comments.
All the other valves tips were at exactly the same height - a straightedge over the valve tips showed less than .001" variation. TFS says the installed height is 1.800.
For the bind test, I placed the entire head into my hydraulic press, set the base at an angle so that the test valve was close to vertical, set a dial gauge on the hydraulic plate, zero'ed it when the hydraulic shaft just touched the top of the valve and pressed down until the spring was fully compressed and I felt extra resistance. That gave me the .790". TFS says coil bind is at 1.080 height or .720 compression. TFS thought I might have gone past basic bind to get my .790; certainly possible with a 12 Ton press.

I don't have a gauge to test spring rate or fatigue; don't care about the old springs as they will all be tossed. Haven't rebuilt that many engines in my life; always just bought new heads and sent them to a machine shop.

Yes, of course the springs don'tt care about the cylinder head brand, but I didn't know how to select a spring so that it has the desired compression at 1.8" height, the correct inner and outer diameter to match my retainers and so on. I see now that pretty much all LS springs have very similar dimensions, are rated at 1.8" height and so on. I have learned a lot in the past 2 days, thanks to the comments here which caused me to further research these topics.

 

It's almost impossible to diagnose a broken spring without seeing it. With that said, there will be too much post fracture damage to see the original failure and we wouldn't be able to give a proper assessment.

If I were to guess, you do not have enough spring, even with the upgraded springs from TFS. You are running a roller shaft rocker which what we have seen, usually needs in the 180 range for seat pressure to control the added weight of the rocker.

I would also high suggest upgrading pushrods to wither a 3/8 or 3/8-5/16 double taper. Install PAC-1222X, should use the same hardware as what you have now. If you are planning on going all new, then go with a PAC-1208X and -0.050 off set lock for a 1.750" installed height.

As much as I love the beehives, I do not believe you will have enough seat load for those rockers. If you swap back to OE rockers, go for the beehives, 100%.

 

Thank you @TurboBuick6 for your additional insights.
I hadn't thought of needing higher seat pressure to compensate for the additional mass of the shaft rockers. Maybe the rockers weren't a good investment after all - besides the $2000 price, I spent another $1K on different rocker covers before I found a pair that worked and didn't leak, and even those required internal clearing. (The shaft "spacers" that e.g. TFS sells leak like a sieve as they don't support their own gaskets and rely on ATF.) Still I like the idea of shaft rockers and have seen good Dyno results.

I do have Comp's HD 3/8"/.080 pushrods; they look like double taper.
I certainly will consider your PAC-1222X suggestion, but the only source having them in stock for immediate shipping is AMS Racing on ebay. Summit and others are 2-3 weeks out. (Update: AMS doesn't have them either.)
Looking at your suggested PAC0-1208X, are your suggesting the .050 offset lock to increase the seat pressure above 150Lbs? Of course you then loose .050 before bind, but they are rated for .750" lift. Didn't know that offset locks exist. I'm learning ever more.
Your signature lists PAC-1276X Beehives, which also look very good, but you don't think they have enough seat pressure for me?