Reparing a BBM head

[bsprowl]

This is not an April fools joke.

The rocker arm assembly hold down bolt insert over intake port 3 broke on my BBM head last week.  Part of the aluminum threads came out with it and the lower part of the insert is still in the head.  This port has the feed hole for the oil to the rocker arm assembly. 
Yesterday I took the head to the three local machine shops; two of them did not want the repair job.  The third wants $800 up front to fix it with no guarantee that it will stay fixed.  They outlined the repair as 1) measuring the angle and location of the oil feed hole before it is covered by the weld, 2) preheating the head to 1200 degrees before welding, 3) welding the pad, 4) machining the pad to the height of the others, 5) drilling and installing an insert and 6) drilling the oil feed hole.  If the head face (and/or other faces) needed to be resurfaced because they warped due to the preheating that would be extra.  I would have to remove the valve springs, etc., before I delivered the head.  They didn’t have the insert and I would have to supply or if they bought it, I would have to pay for the minimum quantity they would have to buy.  They are busy and it will be several weeks before they can get to it.

They suggested I plan on having the valve job redone as the pre-heating probably will warp some of the seats. 

Does any body have a better solution for me?

[e philpott]

I'd call BP and run that by him

[TJ]

Might be able to easy out the remaining insert piece.  I'm curious why the shop you visited wants to weld the area.   I'm not understanding why they don't just drill and tap for a key locking insert.  The key detail is to get the correct angles.

This is a very interesting topic for me because I don't know much about it and want to learn.  I like key locking inserts to repair threads in aluminum and thread locking inserts for iron or steel.  BBM didn't use either in their heads (unless they changed recently). Their inserts for the exhaust ports like to spin out when removing those bolts and I've seen trouble with the insert location you're talking about.  Due to the oiling hole, there is less meat to grip. 

Lot of folks like helicoils but I won't use them unless I feel I have absolutely no other choice. 



   

[bsprowl]

Yes, I can remove the remainder of the steel insert but the aluminum threads in the head holding the insert are paritaly gone and the head needs welding to restore the missing threads. I've got pictures on my phone but I can't get it to link to my computer so I can't show you the damage. 

[TJ]

Yes, I can remove the remainder of the steel insert but the aluminum threads in the head holding the insert are paritaly gone and the head needs welding to restore the missing threads. I've got pictures on my phone but I can't get it to link to my computer so I can't show you the damage.

Sounds like just the threads pulled out with no further peripheral damage.  I don't believe I'd want it restored to the way it was even if they did the work for free...especially if you're not planning to oil through that hole.  For your case, I'd at least investigate key locking inserts and/or find out why they weren't used in the first place.  Honestly may just be my lack of knowledge, but it's a mystery to me. 

[WConley]

Bob -  You shouldn't have to weld the head.  That could cause a whole raft of problems, like wrecking the heat-treat in the aluminum, warpage, etc.

They make oversized repair inserts just for this kind of issue.  Anybody with a good mill or heavy drill press, and some setup patience, should be able to fix that head.

https://www.timesert.com/html/bigsert.html

[jayb]

+1 on what Bill said, there is no need to weld the head.  I have often bored those holes bigger and installed inserts with a 1/2-13, 9/16-12 or 5/8-11 thread on the OD, and 3/8-16 thread on the ID.  See the link to EZ-Loks at McMaster Carr below.

https://www.mcmaster.com/products/ez-lock/threaded-inserts-3~/

If you use the 1/2-13 thread (or perhaps even the larger ones) you can do this repair yourself.  You will need the correct size drill and tap for the OD of the insert, along with a junk rocker shaft and a couple of rocker stands.  Drill one of the holes in the rocker shaft to the size needed for the drill bit, bolt the shaft and stands to the head, and use the hole as a guide to drill the oversize hole into the head.  You can also use it as a guide to start the tap.  This method is not super precise but it works if you are careful; I've done it. 

If you have access to a mill, the angle of the holes is 13 degrees off the deck, so if you fixture the head at that angle you can use the mill to get a nice straight hole, and then a nice straight tap into the hole. 

It surprises me that no machine shop would undertake this repair for a reasonable price, its just not that difficult of a project.

[bsprowl]

Thanks for all of the support. I will have to remove the remainder of the insert and check its diameter and depth which I will share here before buying the Ez-Lok insert to fix this.

[CaptCobrajet]

BP can fix it.  Bring it up here Bob, and we can heal it.

[TJ]

If you're taking the head to Blair, consider taking the other head with you as well and having a better insert installed into that stud hole with the oiling hole.  As an end use consumer, better inserts are my one suggestion for improvement on those BBM's. 

If you're going with do it yourself, when you get to the thread tapping stage, consider starting out with a regular tap and then finish with a bottoming tap to get the threads close to the hole's bottom.

[bsprowl]

I was thinking about changing all rocker arm hold down inserts on both of the heads.  I don't know what is the best insert.  The extra thick wall inserts sold by Master-Carr use 5/8-11 thread which, it seems to me, would be much stronger than the 3/8-16 insert BBM used.

[TJ]

I know Jay linked to the thread locking inserts and I like those for steel and iron.  I like the ones linked below for aluminum.  You'll have to go through the charts to choose the size and thread you need.  McMaster Carr tells you what drill and install tool to use.

If you live anywhere near Blair, I'd consider going there...since it's kinda important to do right the first time.


https://www.mcmaster.com/products/thread-repair-inserts/threaded-inserts-3~/18-8-stainless-steel-key-locking-inserts/https://www.mcmaster.com/products/thread-repair-inserts/threaded-inserts-3~/18-8-stainless-steel-key-locking-inserts/

[jayb]

I was thinking about changing all rocker arm hold down inserts on both of the heads.  I don't know what is the best insert.  The extra thick wall inserts sold by Master-Carr use 5/8-11 thread which, it seems to me, would be much stronger than the 3/8-16 insert BBM used.

For what it's worth I've used the 1/2" EZ Lok inserts in Edelbrock heads that have seen 640 pounds of valve spring pressure.  Bigger will be stronger though, assuming the material is thick enough around the insert.  Also those EZ-Loks have a thread locking compound coating them; they won't spin back out like a helicoil.  jThe thread locking compound is fully cured after 72 hours.  Getting them out requires an easy-out and heat.  I use them in all my cylinder heads.

[CaptCobrajet]

The new BBM heads have 1/2-13 to 3/8-16 EZ Locks.  We can change to whatever you want.  If we set up on the angle, it isn’t that big of a deal to locate each hole.

[bsprowl]

The existing hole is 0.481 in diameter.  There is a mininum of 0.812 inches from the top of the pad to the top of the port.  One E-Z Lok is  1 inch long so it is not a candidate for this repair.

1.  Thin wall:  3/8"-16 installed in a 1/2"-13 hole with a 1/2" installed height.
2.  Thick wall:  3/8"-16 installed in a 9/16"-12 hole with a 33/64 (0.515)" installed height.
3.  Extra thick wall: 3/8"-16 installed in a 5/8"-11 hole with a 21/32 (0.656)" installed height.

I was going to Blair's shop to pick up a set of his ProPort heads so I'll take this head with me and get it fixed.  I post here about what he did when its been done.