Exhaust to manifold joint

[johnmann]

Hi,

I'm after tips from anyone who has worked on this.

The exhaust is blowing from the joint. Normally I would take apart, check and re-assemble. But stuck in my mind is a previous one point five back in 1985. I remember spending a whole day with my friends Steven and David repeatedly trying to get the joint to seal. There was Gun Gum everywhere. We did it in the end but I vowed never to take that joint apart again!  So, has anyone got any advice from experience?  The parts book just shows the external clamp and no other sealing parts.

John.

[canuck]

Hi John,

I sympathize with you. Access to this to do a proper mend is of course carburetors off etc. On my LHD car I also have the clutch/brake master cylinders in my way!

For the record this has to be the most inefficient type of clamp known to man.   However when using OE parts/design, (exhaust manifold and pipe) there is not many options unfortunately.

I had a new front pipe made locally, (in Canada), naturally none available and of course carriage for this part from UK would have bankrupt me. 

The fabricator flared the pipe too big and I needed to grind the circumference of the pipe to just a tad smaller than the cast exhaust manifold receiver flange.  I was able to achieve a tight fit but some kilometers later I started to hear a leak.  Once again off everything came and no issues other than the clamp had come loose. 

I then renewed the clamp as my one was missing washers on the bolts. I tried regular washers on my original clamp but 100% failure. The proper washer, (shown) holds the clamp so much better.

I also determined that the engine moved excessively, (I have since renewed the engine mounts) and the pipe moved about this flange bringing the clamp out of alignment. I put everything back together but this time I installed a clamp around the pipe and used a stiff strap, (bent sort of funky like) between the pipe clamp and fastened it to one of the transmission bell housing bolts.  (like shown below)  

I originally used plumber strapping but a miserable failure so don't be tempted.

My thinking is fixing the pipe to the motor keeps the pipe aligned with the exhaust manifold and free from movement of the motor. A great many thousand kilometres later still quiet.

I didn't use any muffler cement or the like.

This reads as if you will need to break your vow,   I suspect a grinder/Dremel or the like will be needed to clean the interfaces of manifold/pipe.

I hope this helps, best of luck, let us know how you make out.

Bruce  

[tjt77]

so yes..this is a common and irksome problem.. Bruce addresses some of the common issues above.. there are a few 'alternative' design clamps.. some (as made for Ford motor company)  are cast iron with a an enhanced profile that do the job much better..

It cannot be stressed loudly enough that the bracket assy for attatching downpipe to engine backplate is ESSENTIAL..  its also important to check to condition of the flange on the downpipe..if run for even short length of time with a leak, it will often damage that flange, making a complete gas tight seal challenging.... commonly they have cracks and sometimes parts missing ..in which case the only cure is to have a new flared flange and front section fabricated.. most exhaust shops can do this in USA and Canada however..  and may be possible in Uk as well at this time.. 

[johnmann]

Here's a very belated update.

Of the two clamp screws, the outer one came undone easily. The inner one was completely seized, but luckily it had never been properly tightened in the first place! Therefore the clamp could still be removed.  On inspection, it was found to have some rust holes in it. A new clamp of different design (only one screw) was obtained from NTG (see photo). The tube and manifold ends were in good condition, the new clamp was easily fitted and the leak is now cured.

John.

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