Had a Rocker Fail
 

My luck - had a Rocker fail. 2.5 hour cruise home on one motor. Naturally, the motor with Power Steering.....

3600 RPM, just cruising along and BANG. Motors probably only have 25 hours on them. Any thoughts other than just pure bad luck?

(Actually, I feel pretty lucky since there doesn't appear to be any damages other that the clean break on the rocker)


https://cimg5.ibsrv.net/gimg/www.off...5bdff9ded.jpeg
https://cimg7.ibsrv.net/gimg/www.off...bc3b2a3fc.jpeg

Jesel's?

Yes.....

25 hrs on the rockers also? They do have a life span. Aluminum fatigues vs steel. I've seen a couple Jesel rockers broken like that, but they were pretty old and decent amount of spring pressure.

I've got to go back and double check the receipt, but I believe the rockers were brand new in the build......

solid cam?

Solid roller

Might want to check another cylinder to see if you’re getting into Coil bind or something stupid…

I'll have a look, but these are Sonny Leonard built motors so I can't imagine that's an issue. Not exactly a backyard mechanic......!

Wouldn't that have happened sooner than 25 hours? Those Jesel rockers just suck. I've had a bunch of them break on a previous boat... with hydraulic lifters. The other engine in the boat (new build) had the same cams and lifters and Crane Golds. No issues...

Great point/question.

If a/that valve stuck....., cam lobe still rotates, raises push rod (is it still straight?) and weak link expires.

Ugh. I don't like hearing that. Was that on your tiger with the big motors in it?

my thought was they are all on the edge and this spring is shimmed a little more or has a little shallower seat, causing this to fail first with more on the way. Engine guy building one after the next takes a shortcut and doesn’t check every single spring... Unlikely but an easy check

On another note, I am a steel rocker guy, aluminum is just not right for rockers IMO

it was a top gun. My buddy got a good deal on it because it had a broken rocker

LOL...broken rocker on a tired engine. I think both people involved in that transaction walked away happy. That's all that matters! ;):cool: :ernaehrung004:

he did get the rest of the season out of that motor so he was thrilled! Lol hope your doing well in retirement land.

At least it was a clean break right on the end. When they break and send needle bearings into the motor that can cause damage quickly.

I would look at all the geometry and pushrods. Lots of natural deflection in a big block. A new rocker shouldn’t fail that fast. Likely an underlying issue in the valve train

I called Jesel about the known and common failures on these arms prior to using them.
the engineer told me that they break at the adjuster when guys over tighten the adjuster locknut.

i believe the spec is 22 ft.lbs.

he was adamant that this was really important to avoid cracking them at the adjuster.

What's your valve stem to guide clearance? Most heads come delivered set up for the street, you need a bit more for hard marine use.

Just curious, whats your approximate seat pressure?

Is it an optical delusion or is the tip of that pushrod beat up or worn real bad ??

No sure. Ironically, that is the one thing not filled out on the spec sheet.

Optical illusion. I have it sitting on my desk and it is in perfect shape.....

This is good info for reassembly. Thank you. I'll double check this with Jesel, because I have their sheet and it says 26-28.

I also just realized while reviewing the receipts that the rockers weren't replaced. Just lifters, pushrods and springs. That certainly puts more time on these than I had initially thought. I checked to make sure it wasn't a stuck valve and it's not. Thinking I'll try to salvage the last weekend or two of Summer on this drivetrain and might dial them down this winter with hydraulic roller cam and lifters, new rockers etc...... I just don't need 800hp at 6,800 RPM. I need 650-700 at 5500.

this thread has me rethinking shaft rockers, thought they were the shizzle..............

I talked to a Jesel rep at the PRI show last winter.
they now make a retrofit, “sportsman” rocker arm that is steel and has the same architecture as the aluminum arms.
they were in the neighborhood of 100 buck each, if I remember correctly.

Yes. I just got off the phone with him. He confirmed, based on part number, that my rockers were older than the rest of the build. He said they had the sportsman in steel and that would be better for a marine endurance application and that these could be used with the existing stands so that would save a lot. He shipped a replacement for 80$ shipped. Definitely will pull motors this fall and switch to fill roller drivetrain.......

I’d replace them all now. I’m sure the others aren’t far behind.

Replace and run her, season is ending soon for most.
adjust all 32 rockers to specs!.
Good luck.
B38

I only have this weekend and Labor day weekend left. Weekend of Aug 22/23 is soccer tournament and as much as I want to we never seem to use the boat after Labor day so I'm going to replace and hope nothing else fails in the 2 hours I have left on the clock this season......

i visited jesel factory and they said do not screw the adjuster more than 2 turns down i think you could ask them but they did not want the adjuster cup away from the rocker very far i had to get longer push rods

Yes - says operating range is 1/4 turn to 2 turns and are factory set at 1 turn. If outside of that range you need to resize pushrods

A friend of mine broke a few in the same spot also .. seems like those are not the hot ticket I thought they were

You can see in the picture where the break started and "worked" a little, then it lead to the all at once catastrophic failure. Looks like a thin area with stress risers to me. Maybe I've been through too many failure analysis courses at work though.

I called Jesel today. $125 per rocker for the Sportsman Steel Rockers.

I think a set of 16 is about $1400. That's rough.......

A full set including stands is $2650

Just sucked it up and ordered the 200$ valve lash torque wrench. Going to check them all before I see out the season......

So thought I'd just throw this out there as an update in case anyone is ever searching, but quite a few of the adjuster nuts were WAY over-torqued by my estimation. Didn't see any other noticeable signs of damage on any other rockers. I did note that almost all of the adjusters we're about 2.5 turns out but the recommended range is 1/4 - 2 turns.

Anyways, back together and back on the lift, hopefully to see out the summer...... Little guy getting some driving time in......

https://cimg6.ibsrv.net/gimg/www.off...adaef8539.jpeg

Great picture--that is where I hope to be with the grand-kids someday

We Spun those same rockers 9800 in Cup Motors , But yes , we only set adjuster out max 1 Turn, or we changed pushrods , Also the lock nut is 22 FTLB .
If you ran the adjuster out 2 turns , the ****ers woudnt make it off the dyno. But we ran them 2500 miles in race engines . I forget the amount of cycles , Max Rpm 9600-9800.
and Yes we had those cool ass torque wrenches to adjust them with.