Rocker Arm Failure - Would Like Opinions
 

I have never seen this happen. Engine is a 400 w/48 heads running a Crower 60243 cam with Ferrea valves and new springs/keepers, ARP rocker studs, etc. installed a couple years ago. Switched to stock rockers due to Pure Stock requirements and used the Hand adjusting method with poly locks. This was done a couple months ago and car had been driven many times since then.

This happened a couple weekends ago. I had been out on a nice (sometimes spirited) drive through horse farm country. Probably close to 60 miles. Was sitting at a stop light idling fine when engine developed a miss. No noise, just a miss. I thought since it was warm maybe the carb had loaded up. Tried to clear it but no change - had a dead cylinder. Drove the car home and this is what I discovered. Pushrod was fine and lifter still in bore. Installed another rocker arm and readjusted and started up and running strong as ever now.

So what caused the failure? Rocker was old and failed or incorrect adjustment. I did not have an excessive amount of valve train noise at anytime prior or after the failure.

Thanks,

Tom

Maybe the rocker arm slot does not have enough travel for the lift of your cam.

The stock rockers were not long slot and probably did not have enough travel to cover the cam you running. I've seen this happen to someones SBC when they used stock rockers with a performance cam. In thier case it also snapped off the 3/8's rocker studs...

Are they GM rockers or aftermarket replacements?
The aftermarket ones are junk.

Happened to me way back in the 70's...a couple of times...always bent pushrods along with it though...and always at high rpm's. Nice "bang" sound too. Performance cams w/stock rockers...risky

X 2

Spring pressure, cam lift, slot length for cam lift, 50 year old USED rocker, to name a few.

I had Sealed Power brand do that to me back in the late 70's, early 80's. Engine was 400 w/ Lunanti Ram Air III cam, 1.50 ratio. I had three or four fail on me back then. Not sure if it were brand related or not. Went to Harland Sharp full rollers and never experienced another negative valve train issue. Street engine builds, nothing agressive (High 13 to low 14 second 1/4 mile stuff).

Tim john---

Lifter pumped up, due to "Spirited Driving", valve is open and when piston comes up (with the lifter not bled down, it smacks the valve. There is no "give" therefore the thin metal of the rocker pulls apart.

So how did you adjust these rockers with your set-up?

Tom Vaught

I dont see any bluing or such,so the failure almost certainly was'nt heat related.

Next most likely culprits are uneven wear or mechanical interference.

If those stamped rockers were run with any other cam than what your running now,then uneven wear becomes a very likely possibility,often that manifests itself more @ the pushrod cup (PR punches thru the cup),but it can manifest in the fulcrum area as well.

Stamped rockers really are'nt interchangeable/re-useable like roller rockers are,new builds should always get new rockers,and if you change cams,you should also change the stamped rockers as well,as the wear patterns in those stamped rockers tend to take a "set" and they dont always fare that well if those wear patterns change.

Some may also blame those grooved rocker balls too,but I dont think those are what caused this failure,not unless the rockers were used,and the grooved balls were new,as that would be the same deal as mentioned ^^^^ above.

I also agree with those that said to check the rocker slot travel too,especially if using a higher than OE lift cam or such (and of course the Crower #60243 cam is).

Would help to what valve springs ya'll are using on this?

Also,were they new rockers,if so what brand were they?

:confused2

Bret P.

Thanks for the information. The rockers were used, stock items. Valve springs were new with everything else - came from Kaufman and matched to the cam.

Valves were adjusted by tightening the poly lock until the pushrod just stopped spinning by hand then almost a 1/2 turn, lock down the hex nut and then tighten the poly lock.

Didn't consider the lift of the cam causing the rocker slot to have too much travel. There were no marks on the rocker stud. Will have to take a look at that aspect.

I found a set of new Sealed Power rocker arms on my shelf. Maybe time to replace them all with the new ones. Now I need to find a set of the grooved balls.

Tom

I think what you meant to say was that you did'nt consider that there may not be enough rocker slot clearance for that lift cam.

That comment was kinda confusing the way you stated that.

Anyhow,there may not always be witness marks on that sorta deal,those ARP studs are pretty tough (read:hard) material compared to those stamped rockers,so it's entirely possible that the rocker would've been the piece that took any/all of the punishment of said contact.

Nothing inherently wrong with the smooth rocker balls,as a matter of fact some folks actually prefer the smooth rocker balls over the grooved ones.

Me personally,I really dont have a preference one way or the other,I'll use whatever comes with the rockers themselves.

But that's often one of those deals some feel pretty strongly about,so that topic might indeed get some pro & con comments here.

Without knowing exactly what springs & pressures were used it'll be hard to have much of an opinion on that as a possible contributing factor for that failure.

But yeah,used stamped rocker arms are always sort of a crapshoot in terms of if they'll hold up well or not,sometimes they do OK,sometimes they dont last very long at all.

:-ohwell:

Good luck with it.

Bret P.

How used?? I had one rocker do that to me back in the 70's on a fairly high mileage SBC. Spherical bottom just split open. Just old age I guess. I simply went to driveway and got another rocjker from the Corvette builder I hadn't started work on yet and kept on driving.

Bret,

Yes, that is what I meant to say - thanks for clarifying it.

Appreciate your help/insight.

Tom

I'm surprised no one mentioned checking for coil bind. The amount of clearance at full lift varies depending on whom you ask. But everyone agrees that it should be between .040"and .060". I lean toward the greater clearance for the street because our bigger valves are heavy and you're more apt to have lifter pump-up when the springs lose strength. I would never have less than .050.

The slots being too short can definitely cause the problem, as well. If you look at the stud, it should be readily apparent if that's your problem, or not. You can probably tell by looking at the remnants of the rocker, also.

The metal in the rockers is relatively brittle. If they're dropped it can start a crack which will run.

Like I said,without knowing exactly what springs were used,any discussion of those as a potential contributor would be pure speculation @ this point.

If a spring like the recommended Crower # 68404-16 springs were used with the "stock" length valves for those #48 heads and that Crower #60243 cams,one would almost certainly run into retainer to guide clearance problems long before they would ever run into any sorta coil bind issues with those Crower springs.

And the retainer to guide (or seal) clearance mostly depends on what guide bosses those heads have and what VS seals they are using,if they are using PC style seals with the "cut down" guide bosses (and they almost certainly are as the Ferrea valves usually dont come with the second groove in them for the OE style O-ring seals),then IMO there should be plenty of retainer to guide/seal clearance for that Crower #60243 cam's lift.

The only springs that really would have potential problems with coil bind would be a true "stock replacement" spring,and I seriously gotta doubt that KRE would be dumb enough to sell a spring like that to a guy that's using the Crower #60243 hydraulic cam.

So IMO that's probably not the problem.

But I could be wrong,,,I'm not the one that put it all together,,,so I dunno really...

Bret P.

Speculation? No need for speculation, at all. Realistically, it doesn't matter what springs were used or are supposed to have been used. It's very easy to check and one of the first things I would look at.

Thanks for the continued responses. Was out of town on business Monday and Tuesday. Dug out the receipts from Kauffman this morning which will answer the remaining questions from you guys.

Valves - Ferrea 5144 and 5143
Crower 68404 springs
Comp 740-16 retainers
Comp 611-16 locks
Crower 66056 lifters
ARP 135-7101 rocker studs

Tom

I'm surprised no one mentioned checking for coil bind.

X2-My old 409 with a big cam in high school would routinely break rockers(once sendoing a pushrod through the valve cover in the staging lanes and probably caused a dropped valve on a street race-drove it home never found the valve head. Machine shop setup the valve springs. Well fast forward 30 years when I have a vale srping tester pulled them off the shelf and they were in coil bind.

Sorry guys,but there is no way a #68404-16 spring is coil binding with that #60243 cam.

Like I said,with stock length valves the retainer would likely hit the guide boss before those springs would coil bind.

Coil bind for the #68404-16 springs is like .950",that means installed @ 1.600" IH you'd have an easy .600" lift clearance and still maintain a "safe" .050" spring clearance.

And yeah before anyone asks,I've had sets of these #68404-16 springs checked in the past,and they were pretty much spot on what the spring specs said they would be.

He can go ahead and check 'em if he really wants to,but IMO he'll be wasting his time doing that,as those are pretty much the best springs you can find for the 1.600" IH.

FWIW

Bret P.

Brett,

I try to listen to the experts and that is why I bought all new cylinder head parts and cam from Kauffman (based on Cliff's recommendation). He knew how I was going to run the car and matched everything up. I then took the parts and heads to a local cylinder head guy (all he does) and he performed a valve job, put everything together, checked spring rates and installed height and said no issues.

I drag race the car on occasion running 14.2's with terrible 60 foot times due to wheel spin. I keep the rpm's at 5,550 and have my rev limiter set at 5,800 rpm's. Feels like it would keep pulling through 6,000 rpm's!

Took the car out for about 45 minutes today and running great.

Thanks for all the input. I will keep an eye on the remaining rockers and go ahead and install the new Sealed Power set soon.

Tom

Everything that's been suggested suggested was speculation because we didn't have all the facts.

It's not as if you always get the right components in the box when you order something. There's a reason why you check for coil bind when you put an engine together, particularly with mix-matched components. You do do that, don't you? You degree a cam and you don't have as many components from different manufacturers in the mix as what he has with those springs.

It was just a suggestion, I wouldn't have my feelings hurt if he didn't check, and I don't understand why in the world this should be an issue? Particularly since it can be checked more easily than anything else and we're all trying to help someone, right? Unless you think there's something personal in pointing out that it should be done. It's not like we're in competition, or is it?

"Valves were adjusted by tightening the poly lock until the pushrod just stopped spinning by hand then almost a 1/2 turn, lock down the hex nut and then tighten the poly lock."

You need to tighten BOTH at the same time.....trust me it's way better that way. You may have inadvertantly overtightened it. After I get done, I always check the lash on every one once more just to be sure.

If you dont know the history behind te stock rocker arms, I would suspect that the rocker arm(s) may have been at one time overheated due to oil starvation at the ball surface.This may have caused the rocker to get "heat treated" resulting in a loss in ductility/strength. I saw this once on a funny car rocker arm from excessive grinding.

If there was contact with the valve to piston or spring collaspse, I would think the push rod (assuming the weaker component) should have bent, right? Of course, I'm not ruling out other theories, just my few cents worth.