2Heavy4Fast

As the title says, I keep breaking springs, but only on the passenger side, and only 10 or so miles after cam and valvetrain upgrades. Platform is an '02 4.8 ex cab 4dr 2wd, BTR Truck Norris cam (.552 lift), BTR trunnion upgraded rockers, 7.4" chromoly pushrods(BTR recommended), BTR .560 valve springs, LS7 lifters w/ new OEM trays, moderately-ported and milled 862 heads (10.4:1), port-matched stock truck intake, dual CAI at the corners after battery relocation, electric fan conversion, fresh rebuilt 4l60e (bone stock other than cheap corvette servo), BTR "truck yea" converter. 1.75" long tube headers into 20" long 3" collectors then equal length true duals into x pipe then into 2.5" equal lengths to dual 2.5" spintech 6000s turned down in front of rear axle (the drone at 2000 rpm will make your eyes water .) Pre-loaded lifters all between 3/4 - 1 turn past zero lash. Professionally-tuned (his hptuners showed combined over 900 credits but was my first time using him and I have no data logs from the tune but could likely get a copy tomorrow, if needed). Probably more info than needed, but better than too little I guess.

Let the engine reach operating temp then cool completely down twice (sub 2500ish rpm each time), drove it roughly 4-5 miles then made one WOT hit to about 4800rpm and could immediately tell I lost at least one cylinder. Popped the valve covers and had 2 broken intake springs, 1 exhaust spring, all on the passenger side. No valve slap and push rods were fine. Got a P0106 Manifold Absolute Pressure/Barometric Pressure Circucit Range/Performance code so I pulled the map sensor and the o-ring look dry-rotted, replaced it, pulled the pcv valve to also check it as well and when I shook it, it rattled but not like it should have(sounded/felt gunked up) so replaced it, and then replaced the 3 broken springs. Rinse, repeat, then again at about 4-5 miles made an identical hit as before and broke the other 2 intake springs and another exhaust spring, again all on the passenger side, and now again throwing the P0106 code after making sure it was cleared from before, and now that's where I'm currently at and I've been scratching my head until I'm almost to bare skull, since. Now I'm no rocket surgeon or mathmagician, but I'm smart enough to know that I'm not smart enough to diagnose this one on my own because I have no clue what's causing this and I'm really hoping one of you rockstars can give me a reason to dress up like you on hero day. I'm at a complete loss. Going to replace the 3 broken springs tomorrow after work, and tempted to pull the intake off and then go through the torque sequence again just to make sure I don't have a leak somewhere that's rearing its head and becoming an issue with the increase in pressure at WOT. If that is what's throwing the code, if hypothetically a leak be on that bank 2 side could that alone cause enough disruption or anything to domino into an issue serious enough to break springs? Again, I'm just sorta grasping at straws here because I'm at a loss. In advance, many thanks!

Wade

TurboBuick6

iTrader: (2)

You need to check installed height on a few valves and might as well verify lift at the valve. Without that info we can speculate all day. Valve train doesn't care about the tune.

stockA4

I thinki your pushrods are too short for your lifters, but I've been wrong before. There could be somehow some variance in thickness in the block or cylinder head or even the head gasket that's getting the rockers close enough on one side to run on the ragged edge of preload and just not enough on the other side. Again I could be wrong and so much more likely than that, I here that there is often a whole lot of variance in replacement lifters as well for these engines and so that is where I would start looking. some lifters may need significant amount more prelude and you just might need longer pushrods to keep it from falling apart. Many out there are running bTR cams with no issues but they also have the original lifters in there still as well

2Heavy4Fast

What's the best way to verify that? Just cycle it through by hand and use a caliper to measure the difference in spring height?

2Heavy4Fast

I hadn't really considered the lifters being my issue, and the thought of pulling the head back off doesn't exactly make my sticker peck out with excitement, but I do still have the lifters that came out of it and when I took them out I went ahead and sealed them in a bag with some oil just in case something unexpected happened and I needed them again. The top end of the motor has been pleasantly quiet so far with no lifter noise at all so I haven't felt like the pushrods needed to be longer, but starting fresh with the preload again isn't a bad idea considering I'm already right there anyhow. I may just end up pulling the head this weekend and taking a look at the lifters and cam lobes for peace of mind if nothing else. I appreciate the response.

95maroz28

iTrader: (21)

Maybe the btr small .550.560 springs he sells with the smaller cam kits? He told me hes never had one break or reported as broken. Elgin told me to try to leave some extra room say a .595 lift cam and pac 1218s .600 max lift would work but pac 1219s be better before coil bind. I run .625 pac1219s with a .575 lift cam for future cam upgrades.

Full Power

Possibility that some countefeit Xhinese steel inadvertantly "Leaked" into your valve springs ?

TurboBuick6

iTrader: (2)

Should use a spring Micrometer for installed height. For lift, best to use a low force checking spring, dial indicator on retainer and sweep through lift.

2Heavy4Fast

This is actually a pretty good idea and I already have a new set of Melling vs-2257 springs laying around that I was going to use on a different project but changed directions on. I believe they're good for around .600 lift but I'll need to make sure. If I'm having this much trouble so soon, I definitely need to be swapping all of the springs anyhow. Thanks for the idea, I appreciate it.

LilJayV10

iTrader: (39)

That makes absolutely no sense....at all.

Che70velle

iTrader: (6)

You need to figure out your installed height before you go farther. You can throw parts at it if you want, but knowing your IH, combined with your cam specs, will tell you exactly what spring you need.

LilJayV10

iTrader: (39)

OP,

You need to measure your spring install height. After that do the math and figure out how close you are to coil bind.

That's a pretty serious failure with in such a short time span.

I would think you are either in coil bind or got a very bad batch of springs out of the box.

I'm not familiar with those springs. What type of valve seals are you using?

Do they use a factory type valve seal with the locator or does it use an aftermarket PC style seal?

2Heavy4Fast

People have been known to do things a lot dirtier than sell Chinese springs in a BTR box before, so I sure wouldn't rule that out!

2Heavy4Fast

The springs I'm using are the ones that BTR recommended for this cam, but they're spec'd so close together that I should've measured when I installed them just to make certain. Will definitely be doing so this evening when I make it in."

2Heavy4Fast

The cam, pushrods, and springs are spec'd to go together according to BTR, and the springs came with a set of OEM-style top hat seals. I ordered the cam from a BTR dealer/vendor, and then per BTR support's recommendation, both these particular springs and pushrods, albeit from a different BTR source than the cam. I feel like you and as a couple others have mentioned, are right, and I'm probably getting into coil bind. Just weird that it's happened all on the same side, and I still have no clue wtf this P0106 code is fr9m but it only pops up after the WOT hits. Could it just be a byproduct of the broken springs backing pressure up the runners into the intake? I appreciate you taking the time to respond to my post. All of you seem to be in agreement which is what I was hoping for!

stockA4

Hey op wrote a story so I did too 🤣

2Heavy4Fast

Haha this is my first post but not my first rodeo and I didn't want to be one of "those guys" that's like, "Dis truck ain't actin' right, whatchu reckons wrong wit it??" So I wanted to be thorough in my description ha

2Heavy4Fast

UPDATE: I was, in fact, getting into coil bind. After measuring install height I was on average 1-one thousandths out from it, so safe to say that's my issue. To everyone that responded, thank you!!

Che70velle

iTrader: (6)

Thanks for updating this thread.

CattleAc

iTrader: (7)

Ditto.