Proper thread repair?

[BigT]

     I need to repair a striped 5/16-18 thread that secures the rocker base to the aluminum head. Apparently the last person in the motor didn't use a torque wrench! What type of repair insert should be used to do the repair?

[jsachs1]

Heli - Coil will work fine. Part # 5401.
John

[Panzer]

  

[RTMike]

 

[kd]

   X3

[BigT]

Thanks! A friend had told me to use a Keensert because of the heat. I've never used one or have even heard of them until now.

[les]

These are the kits I've been using for years.  The 1/4"x20 requires you to have a 17/64" drill.  The 5/16"x18 requires you to have a 21/64" drill.

[les]

Picture is a bit fuzzy.

1/4"x20 (part number 1208-104)
5/16"x18 (part number 1208-105)

[FLFBRider]

Helicoil or a Timesert.

Timesert's are expensive though. The tools needed to do the repair are 3x the cost of the Helicoil kit.

[BigT]

The bolt had previously engaged about 3/4" to an inch of threads. Do they make longer helicoils?   

[rigidthumper]

I was taught rule of thumb for thread engagement is 2 to 3 times the bolt diameter, so a coil for a 1/4-20 bolt should be 1/2-3/4" deep, a 5/16-18 coil should be 5/8-7/8" deep, etc. Local auto supply houses, Amazon, or Fastenal should have what you need.

[BigT]

 Thanks!

[kd]

   The depth increases as the material strength decreases (ie steel fasteners into aluminum). Steel fasteners into steel, the depth will be the thickness of the fastener between the valleys in the threads.  Steel nuts, unless for special reason will generally be as long as the width of the bolt between the thread valleys.

[Scooterfish]

I`m familiar with the use of a helicoil. I`m not that familiar with a timesert. Would someone explain the major differences and what application a timesert might be preferred and worth the additional cost over a helicoil?  thanks

[PoorUB]

Helicoils are ok for most applications, but for high torque or fasteners that are removed often there are better choices, Timesert, Keensert for example.

Helicoils will "unwind" where the other inserts are sold piece, a small tube with thread inside and out.

https://www.clarendonsf.com/products/inserts/keensert-inserts

https://www.timesert.com/

[Ajayrk]

Timeserts come with a special thread that is usually smaller than the helicoil size pilot hole.
The kit comes with a drill and tap and an insertion tool and a counter sink tool.  In either case; is there room above
the head for drilling and taping?

[les]

  The depth increases as the material strength decreases (ie steel fasteners into aluminum). Steel fasteners into steel, the depth will be the thickness of the fastener between the valleys in the threads.  Steel nuts, unless for special reason will generally be as long as the width of the bolt between the thread valleys.

Just note that you won't need that 3/4" complete thread depth, as mentioned above.  Steel into aluminum, you need more thread depth because of the butter soft aluminum of that head.  The depth of the perma-coils is more than enough the make that torque wrench go "click" in a split second even set to the maximum torque spec.  So, if you have trouble finding that extra long coil, those perma-coils will work just fine.  Also, the rocker housing bolts are not a load bearing situation.  Six bolts torqued at spec is holds that housing down like a brick s#!t house.

[JW113]

Also, the rocker housing bolts are not a load bearing situation. 

Um, isn't the bolts holding the rocker box to the head what the rocker arms are pushing against when the valves open? i.e., they are working against the force of the valve springs, no?

-JW

[cheech]

Also, the rocker housing bolts are not a load bearing situation. 

Um, isn't the bolts holding the rocker box to the head what the rocker arms are pushing against when the valves open? i.e., they are working against the force of the valve springs, no?

-JW

Jw, yes you beat me to it. I agree. On a Twin cam or a Evo, since this is in general. The 4) 5/16-18 threads/bolts do have a great load as you stated. The remainder on a Twin Cam which are 1/4-20, are "cosmetic" so to speak. Hold the lower rocker box in place. They can be tight and the 5/16-18 can come loose/rip out if compromised by being stripped.
On a Evo the 1/4-20 do share some of the load by the way the lower rocker box is designed. No rocker bridge like a Twin Cam.

[PoorUB]

One more comment!

On a TC the rocker arm support bolts go through the lower cover and into the head, the cover doesn't do squat, other than function as a cover.

[cheech]

One more comment!

On a TC the rocker arm support bolts go through the lower cover and into the head, the cover doesn't do squat, other than function as a cover.

Aye, cosmetic.

[les]

One more comment!

On a TC the rocker arm support bolts go through the lower cover and into the head, the cover doesn't do squat, other than function as a cover.

Exactly.  The rocker support bracket is what supports the rocker arms.  That rocker support bracket is bolted directly into the heads.  The rocker housing is exactly that.  A housing to cover all the stuff up.

[les]

So, if you're trying to get 3/4" steel the steel threads on a 5/16" bolt, this means you're trying to lift a car with it.

[cheech]

Some one should of called me out on this.  Hate erroneous info.
The 7/16" external, 3/16" internal hex headed screws Harley uses had me thinking they were 1/4-20 from memory. But in fact all the rocker screws on the Twin cam, bridge and housing alike are 5/16-18 except the breather. Corrected in red.

Jw, yes you beat me to it. I agree. On a Twin cam or a Evo, since this is in general. The 4) 5/16-18 threads/bolts do have a great load as you stated. The remainder on a Twin Cam which are 1/4-20, are "cosmetic" so to speak. Hold the lower rocker box in place. They can be tight and the 5/16-18 can come loose/rip out if compromised by being stripped.
On a Evo the 1/4-20 do share some of the load by the way the lower rocker box is designed. No rocker bridge like a Twin Cam.

Jw, yes you beat me to it. I agree. On a Twin cam or a Evo, since this is in general. There are 4) 5/16-18 threads/bolts do have a great load as you stated. The remaining 5/16-18 on a Twin Cam  are "cosmetic" so to speak. Hold the lower rocker box in place. They can be tight and the 5/16-18 can come loose/rip out if compromised by being stripped.
On a Evo the 1/4-20 do share some of the load by the way the lower rocker box is designed. No rocker bridge like a Twin Cam.