289 HiPo Rocker Stud Torque

[Jbrooks]

Rebuilding my 289 HiPo, and I'm finding different information for the rocker stud torque. Can someone please confirm that I should torque them to 70 ft-lbf. Thanks!

[The Going Thing]

It's 70 FT LBS.  BE sure to use PTFE sealer on the threads.

[6s1640]

According to the Ford Maintenance Manual, the "Valve Rocker Arm Stud to Cylinder Head - 289 High Performance is 60-70 ft-lbs.  The PTFE sealer may act as a lubricant.  I'd recommend setting the torque wrench to 65 ft-lbs.  Give your self a little margin for not over stretching the threads.  Torquing is all about stretching the fastener and leaving it with a specified preload, measured with a torque.

Best of luck

Cory

[Jbrooks]

Thank you guys for the feedback. I'm having issues finding information specific to the k code, as the 289 book I bought doesn't single out the special K code components.

[pbf777]

     I would suggest 55 ft. lbs. as a minimum requirement, and 65 ft. lbs. as a maximum advisable (and probably the preferred), this with the use of Loctite (not quite as slick as the PTFE) as both a sealer and for additional effort in retention, as we have witnessed the stud bosses being split (cracked), not always immediately but perhaps after being put into service, when using the greater torquing sums.       

     I'm not knowledgeable of the grade of material used in the original O.E.M. stud fastener, but if similar to the head or main bolt fastener @ 7/16" x 14T engaging a like cast iron material, that specification being listed as 68-72 ft.lbs. or if using a later aftermarket example, these often being of 190, 000 p.s.i. or more intention which would indicate something even greater in a torque specification, then one if following my recommendation would not be establishing a fastener intended "stretch" value for proper retention, hence the recommendation of the Loctite (I prefer "RED" here), but the concern is for failure of the head casting.             

     Scott.

[KR Convertible]

If you have any questionable threads or just want to feel more confidant torquing the studs, install Heli-Coils.  They are much better than the original threads in cast iron.

[pbf777]

If you have any questionable threads or just want to feel more confidant torquing the studs, install Heli-Coils.  They are much better than the original threads in cast iron.

      I agree with all that is said, but for thought, my posting is of the concern that the stud boss of the casting, which I don't believe was originally intended for this 7/16" screw and the greater force acting upon torquing and also the perhaps increased loading due to a more modern camshaft profile being instituted, with the increased spring pressures and R.P.M., may split.  Although the Heli-Coil product is an excellent choice for the reasons indicated above, one relevant concern is that the function of the Heli-Coil which aids in providing the claimed increased load capacity resisting thread pulling is that it redirects a greater sum of the upward (in this instance) thread pull into an outward push this creating an increased force attempting to expand the casting boss.  Now this is not to imply that the use of Heli-Coils will automatically cause split stud bosses, but it is something for consideration, if the boss is perhaps of already questionable capability in this realm.           

      Scott.

[pbf777]

       B.T.W.  Don't use Loc-Tite in holes with Heli-Coils!   You'll be sorry!         

       And this can also complicate the ability for successful sealing as one has double the number of parted surfaces, and concern for sealers which might not attempt to drag the Heli-Coil out with removal of the fastener.       

       And this seemed like such a simple inquiry by the O.P.!                

       Scott.

[The Going Thing]

The sealer is because some weep coolant, not a lubricant.   You need a thread sealant.  If not, you might wind up with the dreaded "milk shake", or worse.
Ford Service calls for 70 LBS. It's not about stretch, they come loose.

[6s1640]

The sealer is because some weep coolant, not a lubricant.   You need a thread sealant.  If not, you might wind up with the dreaded "milk shake", or worse.
Ford Service calls for 70 LBS. It's not about stretch, they come loose.

Hi The Going Thing,

I am confused about your statement "Its not about stretch, they come loose."  Please explain to me how you can torque these stud bolts to 70 ft-lbs and not stretch the threaded area and put a preload or compression load between the head and the shoulder of the bolt.   The below first image illustrates why a clean and lubricated thread will give you a more tension in the bolt or preload and a dirty or rusty thread will provide a lower load.  That is why care is needed when using a lubrication.  The same torque value for a lucubrated thread will provide a high preload or tension than a dry thread.  This creates the risk of over stretching the bolt and braking the bolt.  Please help me understand what you are trying to say.

My personal experience is with stretched head bolts.  Do not use a stretch head bolt as well as a rocker stud bolt.  If the bolt is torqued outside it elastic range, the stretch will be permanent.  This stretch can be seen with a thread gauge not fitting on the suspect threads.  The same can be seen on the rocker stud bolts if they are permanently stretched.

In the second image, you can see a 7/16 14 tpi bolt torqued to 52 ft- lb. with K = .15 has a huge preload of 9568 lbs.  So a rocker stud bolt torqued to 70 ft-lbs could easily have a preload over 10,000 lbs.  The clamping load is huge.  At these loads, there will be stretch.  This clamping load also creates the needed friction to keep the fastener from becoming loose.

I hope this helps.  Take care

Cory

[The Going Thing]

This isn't a rod bolt. It's designed to stay in place.  If you've ever used any ARP performance bolts that require stretch they use supplied lubricant. They don't loosen up because you use their moly paste.
I have seen a few rocker studs allow coolant seepage into the oil. 

Specification for FORD bolts is 70 LBS.  If you bought ARP or some performance fastener follow their directions.

[pbf777]

It's not about stretch, they come loose.

      It's all about "stretch", as that is the tension that induces the load to create the friction between the two surfaces which then resists the turning movement (loosening).  But just to muddy the water, most of the original O.E. studs, the 7/16" X 14T, is of an interference thread profile, and this is generally practiced when engineering is concerned for extreme situations, and/or that the proper "stretch" for proper retention may not be acquired.             


   

The sealer is because some weep coolant, not a lubricant.   You need a thread sealant.

     Absolutely, a "sealant" is require here (and Loc-Tite can also function as such) as the stud holes enter the coolant area of the cylinder head, but remember, most anything applied to the tread is going to have an effect on the friction value of torquing and should be considered for a proper torquing effect.

Specification for FORD bolts is 70 LBS. 

     Also realize that as not often specified, many torque values as listed are actually "dry" specifications as the engineers didn't have interest in establishing the effects of different substances, lubricants or sealants, on torquing values.  And although one should follow the O.E. directions and specifications, be cautious as more than once the values chosen seem to have been without the consideration of the big picture.             
     
     Scott.

[6s1640]

This isn't a rod bolt. It's designed to stay in place.  If you've ever used any ARP performance bolts that require stretch they use supplied lubricant. They don't loosen up because you use their moly paste.
I have seen a few rocker studs allow coolant seepage into the oil. 

Specification for FORD bolts is 70 LBS.  If you bought ARP or some performance fastener follow their directions.

Hi The Going Thing,

Its okay the rocker stud is not a rod bolt.  It has the same job to perform, holding things together with cyclic loading.  The rocker stud sees a cyclic loading with every rotation of the cam.   The heal/toe action of the push rod and the valve spring put a very large load on the rocker stud to pull it out.  Low performance engines typically use press in rocker studs, but for high performance applications, the loads to pull the rocker studs out are much much higher and need more capability to stay in place.  The enormous preload is also needed to combat fatigue on the rocker stud.  The fatigue strength of a bolt is actually increased with preload.  If the rocker stud preload were in the neighborhood of the applied load for the push rod and valve spring, these rocker stud bolts would be breaking left and right from fatigue.  That is why it is very important to get the right preload, achieved through torquing the rocker stud.  If the threads are dirty or rusty, all the torqued is used to overcome the friction of the poor threads and very little preload is obtained.  This can be seen in the above chart illustrating Torque VS. Preload.

Below is an excerpt from a report by the National Bureau of Standard dated 1962 that had the exact description I wanted to find and share with you.  The report is actually on aircraft bolts that see cyclic loading, but applies equally to all bolts that see cyclic loading, i.e head bolts, rod bolts, main cap bolts and even rocker arm studs.  I found other articles, but this one was right to the point.

I hope this helps.

Cory

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