thread repair, metal glue

Hi

I've been having problems with my mufflet mount bolts comming loose.
This on on a Taipan 2.5cc rear exhaust BB High performance motor.
The muffler design does not mount straight back but at an angle
to clear tank and wings etc when mounted inverted. It is secured only at the cylinder and has always been prone to vibration.

It appears that in a few crashes, the muffler has cantered forward
and distorted the mount faces resulting in the bolts comming loose in flight. I have done my best to lap the surfaces flat and intend to
install a paper gasket as well.

There was a lot of dirty oil on the wing the last time so metal
has been worn off the mount faces and possably the threads.
The threads looks OK and the bolts can be done up good and tight.
I would however like to take up any slop in the threads.

What is the best product to use?

I looked at an epoxy "for a thread" designed for automotive
applications to 150 degrees C, about 310 F.
Is this a suitable product?

What temperatures do our motors run at?

Glue wont wont work. Too hot, well you may as well try, but when you want it fixed right then call All-Weld 805 526-9074 Scott Dinger

Scott has done these before, The customer posted Scotts work here on the forum for all to see and it looked real good.

You could also use a helicoil thread insert, or just go up by one screw size.
Pat MacKenzie

>What is the best product to use?
>
>I looked at an epoxy "for a thread" designed for automotive
>applications to 150 degrees C, about 310 F.
>Is this a suitable product?
>
>What temperatures do our motors run at?
>
>Regards,
>Ken

Ron B.
F4Fguy

Epoxy will NOT work(please,spare me the lecture on JB Weld). Even if the temp didn't exceed 310 F(which it does)and even if the epoxy doesn't melt or burn,it will have,essentially no strength. The only truly effective cure is to machine both surfaces flat and either tap oversize or install a thread repair insert such as a Helicoil(my favorite is Timesert,since it is swaged in place). A soft gasket will only make matters worse.

No "one-upmanship" intended here, but machining both surfaces is essential, prior to getting the fasteners to stay tight. While vibration tends to be amplified at the end of the extremity, the bolts will 'wallow' in their threadbores, loosening as bolt-stretch is relaxed. A 'one step further' would be to change the bolts to studs, (longer-thread bolts chopped off, red loctited into the case, and nutted at the exhaust manifold.)
BMW automobiles have no problem with exhaust manifolds loosening up,(they use studs/nuts) compared to Domestic makes with bolts securing manifolds. Use metal 'crimp' nuts rather than Nylocs.

LAST EDITED ON Aug-08-04 AT 04:11 PM (CDT)
 
Hi Ken,
I would not dare to consider myself an expert in the matter of glues than many here are, but I have experienced your problem.
as you say, "the bolts can be done up good and tight", so you are looking for something to help "lock" them.
I did use JB weld at Brodak's this summer on my header bolts and the problem is still solved. When it cured, it seemed to lock them in well. I am not talking about stripped threads, just bolts working loose as you refer to.
We always put lock tite on our pipe header bolts (like everyone else around here).
Can't hurt to try the JB Weld, worse that can happen is what you have now.
Bill <><