Removing Exhaust Nuts

[R0B]

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[maxstu]

Some have bolts. Some have nuts. You have the worst of the two. Heavily corroded bolts.

I would run a cutting disc between top of bolt and exhaust flange. Get the exhaust out the way. Then much heat and use a stud extractor to remove what's left.

If that fails. Cut thread flush with head and drill bits going no deeper than 25mm.

Start with 3mm and move up a a couple of millimeters each drill. Finishing with a 6.5mm or maybe a 7mm. Then M8 tap.

[Dueller]

I see your into it now with loads of great advice

At best its always a 50/50 if you succeed on getting the nut off, then to find the stud thread is gone beyond repair

Get some cobalt drill bits as maxstu says and be ready

I rebuild the Aircooled engines and have done a DJ wasserboxer and it's the same problem on all

Try and save it then get medieval on it

Sometimes a heli coil or plastic metal will be needed

[Robsey]

I have used heli-coils to make permanent repairs to several alloy castings.
Motorcycle (Honda CB500SW) handle bar switches,
Vectra-C EGR mountings, and many others.
So far, I have been lucky with the wbx engine.

For info, the nearest off-the-shelf drill size for a standard M8 bolt hole is 6.8mm. (Not the heli-coil, as that is obviously a bigger drill size).

Overall, start by taking it slowly and gently,
Then if all $#!t happens, take a deep breath and get a bit more brutal.

[joshmc]

Alrighty well once again thank you for all the helpful advice. The exhaust pipes are now off. Leaving 4 nubs of studs/bolts for me to tackle. As suspected a few the threads are trashed, one isn't too bad but still not great.

I think stud extractor and heat will be the next plan of attack- if things go south I'm also going to ring a few engineering companies just to see what it would cost to have them drill them out. If the price isn't terrible I may save myself the headache. If anyone knows of people based around Bristol that handle that type of work I'm all ears.

The good news is that the 16 head studs came off without a problem, so big win there. Going to check the condition of the heads before I decide if its work fixing up. Low compression and oil pressure started this rebuild, so some inspection work to do.

Thanks a ton for all the advice- more to come I'm sure  

[joshmc]

Forgot to add pics (thank you Rob for showing me how)

[maxstu]

Well done. Heads off too! Crack a celebratory beer.

Now you are at a crossroads. It may well be more economical to buy new heads. Valve guides/stems, valves, cracks in the head, corrosion on mating surfaces, getting out the exhaust studs will all cost moocho money if you farm it out.

Some more photos of valves to see how recessed they are, please.

[Dueller]

Maybe weld a 17mm m10 nut and see if the heat and a good hammer helps, you've some metal to work with there so I'd give it a try

Can't remember if you had a welder or not, sorry

[joshmc]

I dont have a welder, a mate does though so thats an option.

Celebratory beers were drunk and a late start on it today.

Trying to get the heads off without the cylinder liner is proving tricky. Is it ok the pull the liner out with it stuck to the head?

[maxstu]

Yes, it is okay. However it means the pistons will need removing from their conrods for rebuilding.

They require reinserting into their appropriate sleeves before slipping back on conrods. Cylinder one sleeve should go back on piston one. Cylinder two with piston two etc.

And each piston has an arrow on it's crown to show which way round it should go.

[joshmc]

Managed to slide the cylinders back in, so heads are off and had a clean up.

The reason for the rebuild was low oil pressure and compression. It was low across all cylinders but particularly bad on cylinder 3 at about 60 psi.

Having had a look at the heads I think (in my 0 years of experience doing this) they look really good. No cracks, pitting etc and still very flat.

Cylinder 3 is the head with the light brown colouring on the valve, not sure if this could indicate a reason for the low compression?

Either way I'd appreciate someone with a more experienced eye having a look and offering an opinion on the head conditions. Going to be taking the cylinder liners and pistons out either way, so if its seals etc I will get it them.

Cheers max and others for the thoughts as always! Wouldnt be able to do this without the guidance so thank you all!