pesky rocker arm bolts

[hce]

Broke an exhuast rocker arm bot, driver side, week ago. Extracted the remains with a left hand drill bit. Today another one broke on the passenger side intake. Remains came out with a screwdriver. All the bolts were on the loose side, 15ftlbs. Not sure whats going on, all bolts were torqued to spec last spring when engine was rebuilt. hopefully the new bolts will prevent further breakage.

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[Thewespaul]

How long since your torque wrench was calibrated?

 

[hce]

I compare it with an electronic one each time, so it would take two being off. Actually 3 including the 3/8 torque wrench.

 

[Thewespaul]

I wonder if they were just stressed from being over torqued by a previous owner? I usually only have issues with them rattling loose with high rpms never had one break on me.

 

[RDieselKid84]

Wes, how often should you check the rocker bolts torque.

 

[frankenwrench]

I had several break on my 6.9 when I was building it a few years ago just after I studded it cause I had also just broke a head bolt! Not sure about why my bolts were breaking either. Only thing I can think of is maybe my block had been overheated badly before I got it.

 

[hce]

I'm leaning towards the bolts were stressed. I should have noted that the second one was in three pieces. When screwing out the remains got one short chunk about a 3/16" long followed be another pieces. The two pieces are in the picture. Maybe the 910 valve springs over the worn stockers was a tipping point on 30 year old bolts. I should pull the valve cover again and check rocker arm slot, and valve travel, due to new rockers and a different cam grind.

 

[Thewespaul]

I install them with blue locktite now and don’t have any issues with them coming loose now

 

[hce]

I install them with blue locktite now and don’t have any issues with them coming loose now

The thought entered my mind.

 

[Thewespaul]

The thought entered my mind.

What lifters did you use when you rebuilt it?

 

[hce]

What lifters did you use when you rebuilt it?

I believe sealed power. Checked preload at the time, seemed reasonable, can't recall the numbers though.

 

[Thewespaul]

I’ve seen the enginetech Chinesium lifters stay stuck and not compress like they should, that compounded with an aftermarket cam I could see that working against the rocker bolts and breaking them, but haven’t had any issues like that with sealed power lifters... if you continue to have them break I would replace all the bolts and take a peak at the lifters to make sure that’s not causing issues.

 

[icanfixall]

May want to check spring height and possible spring binding seeing you replaced old springs for new 910.

 

[YJMike92]

Seems to me heavier springs and a reground cam will exert different pressure and stress on the old retaining bolts. I would suggest all new bolts at a minimum. Then I would turn the engine over by hand and make sure rocker and valve operation appear normal. I would think there would be some specs somewhere for maximum spring compression. Frankly, I would be wary of the reground cam. If all the bolts were loose maybe they are all stretched

 

[hce]

Not coil binding. Possibly retainer bottoming on valve seal. Checked cam specs valve lift and it is only .030. Failed to explain in original post the new bolts meant 16 new bolts.