[Banditogto]

What would cause full Roller Rockers to break at the trunnion? I have one that completely came apart and upon inspection, I discovered several others that are cracked/split at the trunnion right by the stud hole. Anyone ever experienced this? The Rockers are 1.65 PRW's.


Engine:
488 CI
Bore: 4.155 Stroke: 4.500
Cam: Comp Int: 270 Exh: 279
Lift: .660 (1.65 Rockers)
Edelbrock RPM Heads Ported
Port Matched Victor Intake
850 Demon

[issach428]

i had one come appart on me and i thought it was a freak failure, upon very close inspection at full lift the pushrods were tapping againts the trunion alot. So that could be something to check. Oh and lack of oil could do the same thing.

[mechanickeith]

Valve Spring bind???

[screamingchief]

Incorrect rocker geometry/pushrod length that has the stud biased too far to in the rocker slot,thus as the rocker approaches full lift it runs out of slot in the rocker arm and consequently binds the rocker arm on the stud.

That or as mentioned valve spring coil bind,or some other mechanical interference (guide to retainer) issue.

A pic would help us understand the failure better.

Did it break on the underside of the rocker,or elsewhere?

Did it also bend the pushrods on those locations???

What springs are being used here?

What sorta seat/open pressures??

Fill us in and you'll get better feedback.

[Cliff R]

Are they aluminum or the steel ones?

I've seen some brands of aluminum rockers like snapping twigs, but always on really high rpm/high hp stuff with extremely aggressive lobes......Cliff

[Half-Inch Stud]

Perhaps:
0. Valve is hitting the Piston?
1. ValveRetainer is hitting the Valve Guide?
2. Outer Spring Coil Bind?
3. Inner Spring coil bind?
4. Exhaust Guides too tight?
5. Loose-Lash causing pushrod to hit off-spot in the Rocker cup?
5. Tight lash + lifter pump-up causing bind (see 1&2&3)?
5. genuine replacement rockers made from recycled BBQ grills?

[PONTIAC DUDE]

The PRW's are 6061-T6 extruded aluminum as listed in their catalog. I don't know if that means Cast or Forged, but can make a BIG difference. Also depending on your open pressure too.

Are the pushrod holes elongated as most E-head will have some interference in the hole with that ratio. This can put the tip of the pushrod in a bind under the rocker end. I don't see retianer to guide as an issue with e-heads and that lift as long as you use the std 2.213 long valve min.
I take it Piston to valve was checked with that 4.5 stroke?
Coilbind could be an issue depending on the spring and height used.

[Ron H]

Extruded is not cast or forged. It is extruded then tempered to T6. 6061 is a very strong aircraft grade alloy.

[Banditogto]

Well, I finally got around to taking some pics. Two of them completely came apart, three of them are split, the rest look fine.

[screamingchief]

I'm not much liking those guidplates,so for now I'm gonna blame them for this.

It looks like the guideplate either was'nt aligned properly @ set-up,or they may have shifted @ some point during running,and thus they loaded the roller axle unevenly and that caused the axles to fail.

Excessive lash may also be a contributor to that as well.

All/any of the times I've seen that style of guideplate used successfully,they are set-up and aligned first,then they get tack welded in that middle bar to keep them from shifting around afterwards.

[PONTIAC DUDE]

With the discoloration of the needle bearings and shaft. I would suspect 3 things.

Lubrication

Load

Too much spring pressure for the rocker make.


Did this have a stud girdle?

What springs, retainers & keepers are you using?

I would also recommend tack welding the guide plate after you set the proper geometry.
Ya need to mod the drain back holes.
A lot could have to do with the bearing itself and possible treating & clearance from the factory.

I have put roller rockers thru some severe use over the course of 40 plus years and most issues are at the tip end. And that over long term use.

[Banditogto]

Thanks for the responses guys. Here is some info on the valves and springs that are installed on the heads. I would also like to add that I'm also using a roller cam.

Manley custom 2.150 intake valves and Manley 1.6 ex valves, springs are Manley 22440-16 Nextecks and retainers&locks comp 741-16 and 613-16, spring seats are Comp 4770-16, installed hieght is 1.850 spring pressure is 250lbs on the seat and 660lbs open at 650 lift

[tiacguy]

6061 is not aircraft grade aluminum. 7000 series are. From what I can see its not the aluminum that failed. Its the steel fulcrums. Id say the rockers arent rated for your spring preasures.

[Overkillphil]

I have the same rockers on my new 462 which I haven't installed in the car yet. That little voice told me to go with the other choice at the time (Scorpions) but I let someone talk me into these.

I have no warm fuzzy feeling about these Chinese rockers at this point.

[PONTIAC DUDE]

Might cost a little more but have used H.S. for over 20 years and so far not one issue. Even healthy rollers with 700 lb open in my old nitrous 90's combos.
Current CV-1 solid roller is 693 open and will be using 1.7 H.S. with a stud girdle.

Yes I would look at a better rocker for your application. Thanks, for the info.

[Banditogto]

Ya know the sad part is, I was only able to make three passes with these on my new motor before they failed. Now I have to remove, and tear the entire motor down to see what kind of damage this has caused and try to recover all of the bits and pieces.

[Brian Baker]

Regarding the guide plates, once their alignment is set up, they should be tack-welded together (see pic where they "tab" into one another).

[PONTIAC DUDE]

Originally Posted by Brian Baker

Regarding the guide plates, once their alignment is set up, they should be tack-welded together (see pic where they "tab" into one another).

Dolp.


*********** Read Post #11 ************

[Skip Fix]

Those look like the Isky guide plates. Look CLOSE at full valve lift that the slot is deep enough for the pushrod not to hit the bottom of the guide plate. My RAIV heads with 3'8 pushrods would not work with them for that reason even just using a 1.6 rocker. In fact they hit I think even with no lift.

[455-4+1]

Good point Skip

I had to clearance the back of the slot with the Iskey adjustable guideplates to fit a 3/8" pushrod. When doing first assembly on a new valvetrain check all clearances to everything moving over several rotations., ant binding, pushrod clearance, rocker slot, retainer clearance, guideplate clearance / alignment etc etc

It may turn over by hand OK with minor issues but zing it to 7k and see what happens !!!

One of the little angle neck mirrors and a flashlight or even a non coated paper clip can be usefull