nmccann

iTrader: (1)

Guys,

Figured I'd throw this out to get your opinions here.

370" LQ4 based engine
Edelbrock E-cnc 215 heads
Speed inc TU1.5 cam (.571/.571, 228/228, 112LSA)
BTR .660" platinum springs (steel retainers), 155lb on seat ~380lb @.571"
5/16" comp push rods
1.72 Comp Ultra-gold rockers (pedestal mount)
Billet wheel PT-7675

That's all the important stuff I think. One of the rockers failed a couple of days ago. As you can see in the pic the tail broke right off. This isn't a new build, there are a few thousand miles at least and I've revved this thing to 7k more times than I can count.

Springs appear to be fine. I can get the valve off the seat pushing on it, super stiff, feels the same as the rest, as empirical a test as that is lol. Swapped a good rocker in place of it and compression is fine, same as the rest. Spark plug is fine, push rod is straight still as well.

What do you think? Isolated incident or should I be looking at replacing these with a different type/brand? I've always had great luck with comp cams stuff.

svede1212

iTrader: (3)

Everything else may be fine. I've seen failures with every rocker but Yella Terra seems to be the go-to in the mid-priced range roller. Have you checked all of your push rod lengths and what lifter do you use?

nmccann

iTrader: (1)

All of the push rods look fine, aside from the one that bit the end off that rocker, it's a little scuffed up but still straight. They're 7.400" long. I'm not positive what lifters are in it, I didn't build this engine, a shop did. I do remember them saying they were comp as well, they still use the stock buckets.

JakeFusion

iTrader: (7)

Aluminum fatigues over time. Depending on how many miles/heat cycles were on the rockers, it could just be age.

Or, it could be an out-of-control valvetrain that beat up the rockers over time as the lifter lofted and the pushrod cup of the rocker took the brunt of the force. Those springs are probably too light for the weight of the rockers. Tooley sells a max pressure version with a 450lbs open pressure to control the aluminum roller rockers.

Exidous

iTrader: (11)

I would consider thicker pushrods with almost 400lb open pressure. The pushrods pole vaulting could strain a rocker. 3/8" if you can fit them as the are pretty cheap. 11/32" if you can't.

vettenuts

iTrader: (4)

I would also ditch the wimp 5/16" pushrods for a larger OD. Also, as stated, aluminum has a much lower fatigue life than steel. Revving to that RPM, in my opinion, would require new rockers whenever you refresh the springs.

HioSSilver

iTrader: (8)

That sucks.....I've seen hs rockers fail. I attributed that to the springs because i have run hs rockers for probably near 40k miles......and i spin to 7k to. I have run stock ls6 springs with them and psi beehive springs. The ones i seen fail was on a double spring. To me if you gonna improve these engines you don't back up to a double spring. Use beehives or better yet conical and ti retainers.

redbird555

iTrader: (14)

I don't think the springs being too spring here caused the failure Hio, the springs may be heavier than a beehive but as long as the keep the valvetrain in control there shouldn't be issues. They have roughly the same open pressure as a psi but more seat preesure which should help control quite a bit.

I'm inclined to go with the pushrod pole vaulting at 7k and aggressive cam lobe beating up the rockers

Darth_V8r

iTrader: (4)

I agree with red. Pole vaulting is much higher strain because it adds to the spring pressure, and it's on the short side so multiply be 1.7.

Makes you glad you went larger PR doesn't it?

HioSSilver

iTrader: (8)

I can agree with that.....and that was my point. Less control in that valve train set up. My friend broke up a set of harland sharp rockers i had run for years with similar springs. When you spring needs a dampner spring something is wrong imo.

The rating on op's springs are similar to my psi springs.

JakeFusion

iTrader: (7)

I don't know what the engine was exposed to, how well the Comp rockers are made, or anything. But he doesn't have stock cam lobes. He has pushrods that look like noodles on a spintron. He has a spring not designed for the weight of the rocker on an aftermarket lobe. There's lots of possible issues.

I would move to an 11/32 pushrod and stock rockers with BTR upgraded trunions on the rebuild.

69-chvl

iTrader: (11)

Could just be a defective rocker. Doubt a push rod would have anything to do with that. How's the piston/valve clearance? How far from coil bind are the springs set up to?

But IMO I suspect the rocker had too many voids/casting issues in the alum and let go. Maybe Comp can look them over for you.

nmccann

iTrader: (1)

I suspect you are right. Springs are installed at 1.78" to get 155 on the seat, coil bind is at 1.13", tons of PV clearance .150"+. Chatting to my engine guy as well and he seems to be of the same opinion, told me he wouldn't sweat this much and to just change the rocker. I do appreciate everyone's replies on the matter as well. I am going to see about a warranty rocker but rather than wait a few weeks and let the summer pass I went out and bought another set to get the car mobile again. Based on the revised design of the new ones I suspect I'm not the only person that's had trouble with these... Those of out there with YT rockers, how similar is this to what you have?

Also, I had to grind the hell out of my valve covers to get enough clearance for these. Everything else remained the same, wipe pattern is good, no shimming req'd and the same pushrod length still works.

Exidous

iTrader: (11)

That's a huge difference in material. Are they the same party number just a diff rev?

Darth_V8r

iTrader: (4)

Regarding the covers, I used a really thick gasket to gain space. FWIW

HioSSilver

iTrader: (8)

Wow....i thought they made them lighter. That don't look lighter.

A.R. Shale Targa

iTrader: (2)

I just noticed this application has one of those snail shaped muffler thingys...
I'm guessing the rocker that broke is from an exhaust valve, trying to open against all that insane cylinder pressure

Exidous

iTrader: (11)

15lb of boost on an intake valve @ 2.1" reduces open pressure avail by 52psi roughly. So at 15lb of boost you are essentially running a 330lb spring.

nmccann

iTrader: (1)

Same part number. There isn't anything in the literature on comp's site about a revision and there's nothing in the paperwork that came with the rockers. The first set are a few years old, this engine sat a long time before I got my hands on it. They sure don't look any lighter, that's for sure.

The rocker that broke was on an exhaust valve. Funny thing is that it let go putting down the road in front of my house. I figured for sure it had dropped a valve by all that banging and clanging that started, pretty scary.

Thanks for the info about the thicker gaskets, didn't know they were out there at the time.

TurboBuick6

iTrader: (2)

nope.