289K cast-in pushrod guide issue

[Bossbill]

A few (4 or 5) of the cast in guides in my 289K heads have worn out and the slots are now oblong (sideways). The heads need to be gone through anyway.

From a 'keep this engine as stock as possible' point of view do I ask the machine shop to drill out just the pairs of pushrod guides on one cylinder (pair) and just run guide plates on that cylinder only?  Do them all? Or is there a fix of which I'm not aware (drill out and press in a newly machined guide).

I'm leaning toward a guide plate conversion.

[shlby66]

I'm leaning toward a guide plate conversion.

     +1 That's, what I did, on my HiPo 289 heads. No Problems.

      Doug

[roddster]

   If just a few wore oblong, how long do you figure the others might wear?  Might a well fix them all, permanently.

[pbf777]

I'm leaning toward a guide plate conversion.

     Yes, machine the heads to accept guide plates.           

     But now, particularly associated with the stud boss height, what would be the ideal sum (number) to be milled down from the stud boss?               

     Hint: for "ideal", the answer is not quite as simple as it may seem.   And the, "That's how we always dun-it", ain't the right answer, as remember, your now the new engineer, so think about it!                         

     And since I don't want to have to type in all the B.S. (maybe, I could just google it and copy/paste it?), I'm hoping someone else will!                

     Scott.

[gt350hr]

    Scott,
       On a HiPO head that is factory machined for studs , I have used the Ford ( now obsolete) C9OX plate. It is only .060 thick IIRC and has no affect on rocker geometry , nor will the rocker "bottom out" on the stud. A thicker "aftermarket" guide plate "could" require  machining I suppose.
    Randy

[pbf777]

    Scott,
       On a HiPO head that is factory machined for studs , I have used the Ford ( now obsolete) C9OX plate. It is only .060 thick IIRC and has no affect on rocker geometry , nor will the rocker "bottom out" on the stud. A thicker "aftermarket" guide plate "could" require  machining I suppose.
    Randy

      Hey Randy,

      Yep, I'm aware that the H.P. head is machined for the screw-in stud, and agreed the stud boss height does not affect valve-train geometry (in the typical sense), unless one chooses to adopt a poor set-up to allow for an interference issue of course.     

      And agreed, I never said one was required to, or even perhaps should, machine the stud bosses, as this is what one needs to determine, and as your fitment information provided are some of the relevant concerns.       

      This is the same consideration that should be given for the the 429/460, early C8, C9, & DOVE castings when choosing to "convert" to adjustable studs, as these are also already machined from the O.E. for a screw-in, but "bottle-neck" stud and addition of guide plate installation.           

      Scott.

[Bossbill]

I just pulled this stud out of my HiPo head.
The stud does not have normal threads (see tap).

What thread style is that?

[shelbydoug]

The FORD STUDS are not cut, they are rolled. That's what you have.

The AR's are too as I recall? I don't have a set in front of me to check right now to verify though.

Stock 289hp's are not highly stressed. There is more an issue of not stripping out the threads on the rocker arm side.

The rocker arms are going to wear through the tips before the studs ever fail.

[Bossbill]

I understand that most threads are rolled, not cut.
However it's the style of the thread that's interesting. V-shaped threads are easy enough to roll, so why this style? Less stress into the cast-iron boss?
An ARP stud will not go into the stud boss without re-tapping it. At least I didn't want to get too happy with my tap ...

[pbf777]

I just pulled this stud out of my HiPo head.
The stud does not have normal threads (see tap).

What thread style is that?

     I'm sure there is a proper and specific technical engineering name affixed to this thread profile, that is with the square minor or root profile, but as I stated previously, most of the O.E.M. examples are as such, an "interference" thread.  Also one may encounter a similar thread profile coupled to a triangular shaped O.D. of the stud's diameter. 

     In this application I feel there are a couple of intended benefits for this interference thread; first the obvious value of fastener retention as discussed previously, but also since the cylinder head is tapped for a different thread profile the softer cast iron material is then displaced as it engages the stud, this not only providing the mechanical locking feature, but also disruption of the clearance between the two thread surfaces which would otherwise act as a fluid channel (leak).  Oh, and since the minor diameter of the stud is increased, a probable increase in the stud strength as most often the fasteners failure begins in the root of the thread.               

     So yes, one should run a "thread forming" tap thru the holes before attempting to run the yes "rolled" but different thread of say an ARP fastener in.             

     Also for consideration is if in the operation of the placement of the O.E.s interference thread intention, with the require process of displacement of material accomplished, what effect is presented on the turning torque in order to acquire the same fastener preload sum, and that effect on the as specified by the O.E. torque specification, when installing a non-interference thread fastener such as the ARP, with something on the threads?           

     Think about it!                 

     Scott.

     

[gt350hr]

   It was /is my understanding that the special thread on the stud was designed to seal better and reduce water migration without copious amounts of sealer being used. Not as flowery as Scott's reply.

[pbf777]

    Is anyone truly aware of whether the original assembly by the O.E. involved any sealer?         

    "FLOWERY"............  I guess it's being suggested that I perhaps need to move to one of the horticulture forums!           

     Scott.

[gt350hr]

       In "my experience" the first design (3/4 wrench size) studs did not have sealer at all. "Some" of the second design ( 5/8ths wrench size) did , but not "all". I am talking about known "original" heads that had never had a stud out. Ford had some issues with pushrod alignment and many studs were cut into by the rocker arms or the guide in the head wore as in the OP's situation. Individual stud replacement was fairly common "in the day".

[pbf777]

    That is as I observed , no thread sealer material on units that I felt were unmolested, but was undecided on others which did have.             

    I attempted to make that as "UNFLOWERY " as possible!             

    Scott.

[gt350hr]

    Just keep the cats fed , nothing else is as important.
By flowery I meant I wasn't used to you using so many of those fancy words you used. All good.