Stripped headbolt

[HarryL]

Help me here !!!!
Got to 90# and the thread in the block gave out !
You guessed it-one of the deep ones !
I know of Helicoil; but how can I get way down in
there to do the repairs ?
This is the freakin pits.
Harry

 

[HarryL]

More info-
It's on a tr4a block; the long bolt by 3/4 pistons on the
intake/exhaust side. Do you think I can helicoil a
short bolt like the others ?
Harry

 

[DougF]

Been there.
I pulled the head back off and was able to drill out the hole with a borrowed mag drill and then retapped the hole. I used a Helicoil but would have preferred to use a keysert. I couldn't find the proper size on short notice.
I would strongly recommend using a keysert.

 

[HarryL]

Doug,
Thanks for replying. This bolt is one of the long ones that goes way down in the block- how did you reach it with the tap,etc. ?
Harry

 

[DougF]

Are you referring to a stud holding the head?

 

[HarryL]

Yes I am.

 

[DougF]

Extra long drill bits measuring 9" & 12" are available, as are pipe extensions for taps. I don't know if McMaster Carr carries them, but I would check there first.
Not knowing how much metal can be removed in this area, I would use a Heli Coil which require less removal than keyserts.

 

[HarryL]

Great !
The hole bottoms out at about 5 1/2 inches so the drill bits
and taps would do fine. Have a helicoil in one of the race engines;
but never put one in. Can you get it down that far and set it ?

 

[DougF]

Yes, that shouldn't be a problem. There is a straight wire end to the inside of the Heli Coil that should allow you to run it to the bottom with a spade screw driver as long as it isn't boken off.
You can check, there may be a 6" length drill.
Good luck!

 

[KVH]

Here's my question, scary as it sounds:

Is the best and safest course of action to remove the engine and transmission from the vehicle, remove the head from the block, and take the block to a machine shop?

I can't imagine messing up the drilling, ruining the block or negatively impacting head torque, but I'm a worrier.

 

[DougF]

The mag drill is key to getting things right. Once everything is set up, the magnetic base is locked it into place and it won't move.
If I were to take it to a shop, I'd probably trailer the car and let them do the work with the engine in place.

 

[Got_All_4]

I'm with KVH. That's the safest and best way. However many machine shops would install a Time Sert. A Time Sert is a full insert that is pressed fitted inside the hole you drilled and tap. In fact TS uses the same drill and tap sizes that a Heli-coil uses but you can torque to original specs.

The problems with Heli-Coil and Time serts or any inserts is that you are going to have to be perfectly square. If not, you'll never get the studs screwed in and you'll have bigger troubles. So something as critical as your head, leave it to the professionals.

 

[HarryL]

Sounds great guys !
Will call the machine shop today.
Engine's on a stand,so will strip it down and take it to
him. On to the next part.
Again- thanks
Harry

 

[MDCanaday]

I try the easy way out( first) myself.In this same fix once it was found that you can thread the stud further up the shaft with the correct die. Then after cleaning the threads in the block,running a tap as far down as possible,the stud found enough new threads to work.You can also buy some sleeve sealer which is a locktite product to glue in a steel sleeve to a block.It will help too.If then this should fail too , I would let a machine shop set keysert....
MD(mad dog)

 

[HarryL]

Ok guys,
Talked to my machine shop and we're
concerned about getting the helicoil down into the
block(about 5 1/2") and resting perfectly.
Talking about using a short head stud and fitting a
keysert. I'm wondering what effect this would have
on the head/block. This is strictly a road car so
performance is not that much improved over stock.
Thoughts on this action anyone ?
Harry

 

[TR4nut]

I'm not a mechanical engineer type, but I think you could torque the head with that fix - but my guess is what you would loose is that the block itself below the fix would not be in compression like it was with that deeper stud. I have no idea though if that is a fatal issue or not.

 

[HarryL]

Hey Randy-
Give ya a call am.
Are you going on the Ok.Run ?
Out in the bay 35knot winds with 1/2-1 mile visibility
Later
Harry

 

[TR4nut]

Sorry Harry -

Missed this note and your call - our internet was out at the house and just now got fixed. I'll try to catch up with you via landline.

Randy

 

[Tr4dude]

you could try a diesel machine shop, i worked at one and have done this repair several times. the depth of the repair on diesel blocks are deeper than automotive and they may be able to match something up for you.

 

[HarryL]

It worked !!!!!!!!!!!!!!!
Got the machine shop to put in a helicoil
like Doug said. Torqued down to 100#'s and held.
On to the next dilema.
Have a great weekend everyone,
Harry