friggin exhaust manifold studs!

[Ben Swann]

I usually find getting the manifold off without a few stud snapping off inside the hole is rare.  But usually only 2 or 3 are in need of removal and repair via helicoil/threaded inserts.  

There should be nothing wrong with the threaded inserts, if they were installed correctly.  I would ascertain the nature of the problem.  If the small tab used for installation was not broken off on this, do that - take a small chisel (even a screwdriver should work) and break off the tab.  The tab will cause a sutd to just keep scrwing the coil in deeper.   If the correct size coils were used, they should be stronger than the original aluminum.  NASA does this regularaly with aluminum parts  - they'll take a perfectly good aluminum part fastened with studs, disassemble and Heli-coil them for added strength.

It is possible the installer used the wrong size drill bit to install the coils.  I this case you'll have to extract them and install another size coil and go up to another size stud, or?.  Let us know what you find.   Perhaps we'll have some suggestion to getting it right, probably extracting the coils that are in there and installing a larger size and/or?.

Ben

[Ameer Antar wrote:

> Ya, it looked like steel coiled inserts. They were all like that. When 
> I was tightening the studs in, I was a little worried about going too 
> deep as I didn't want to go too far and hit a water passage or 
> something. Each stud seemed to tighten a little differently.. 
> depth-wise. So if the inserts are spinning that means they've come 
> undone, or what? What's the solution? Bigger thread? I don't think the 
> holes in the manifold will handle bigger bolts. What else? Can these 
> things be welded??? Man this is sounding scary!! HELP!!
>
> -Ameer
>
> ----Original Message----
> From: Eric Sanborn <eric_audi.ql at mindspring.com>
> Date: 7/1/04 11:01:18 PM
> Subject: Re: friggin exhaust manifold studs!
>
> Ameer Antar wrote:
>
>> The threads in the head all looked like spiral-locks, but I figured 
>> that must be the design since it's an aluminum head, and all of em 
>> had it. Hope someone can offer some help... TIA.
>>
> Do you mean like helicols in each bolt hole?  I have never seen a VW 
> head with them.  I would guess it was a repair, but it would be 
> strange to have all of them that way.  Both my I-5 (KH, JT) are just 
> aluminum threads and my countless VW 4-cylinder heads are all just 
> aluminum.
>

The threaded inserts I have seen in the past require tapping to a 
special larger diameter and then installing the insert into the hole.  
The bottom of the insert has a small cross piece to it that the driver 
uses to install the insert.  Once the insert is fully seated this piece 
breaks off.  This allows you to thread your fastener deeper than the 
insert and I believe it locks the insert in place.

When you turn the studs in the head to the inserts rotate also?  If so 
do they translate or thread into the and out of the head or just spin?  
If they just spin you have a problem.  If they translate in and out you 
might be able to work them out some and then loctite them back in.  Just 
don't go overboard on the amount of loctite or it will work to the ID of 
the helicoil and you will also be locking in your studs. 

If they just spin then they sound like they are stripped.  This is a 
problem since if they spin they will likely pull out during the first 
heat cycle of the exhaust manifold.  Remind me are the studs M8?  If so 
you would have to jump to M10 which is quite a jump.  I know it would be 
sad to mix and match, but maybe switching to 3/8" helicoils would work.  
A 3/8" bolt is 0.060" bigger in diameter where as M10 is 0.078".  
Remember that if you do you will have to insure that all the holes 
clearances remain unchanged.  The center two holes are fairly close 
fitting as they locate the manifold.  Every other hole has a loose fit 
to allow for thermal expansion.  Of course you would also have to find 
appropriate heavy washers.  I don't know if it can be done with the 
space allowed.

I guess the most expensive option would be to weld the holes shut and 
then get them redrilled and tapped, but this would require the head off 
the block which would be I sure the last thing you want to do.

One more option and this one would be classified as serious project 
scope creap.  Make your own manifold that can accept M10 studs.  Of 
course this means the CIS has to go in the garbage (where I wish mine was).

Keep me posted.  I feel for you.  These 11 hour problems on a big 
project can be disheartening.

-- 
Eric Sanborn
'85 4ktq

http://sofadog.net/4ktq/]