Exhaust manifold removal

Engine Oily Bits, Ignition, Fuelling, Cooling, Exhaust, etc.
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simon.williams
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Exhaust manifold removal

#1 Post by simon.williams » Sat May 17, 2025 5:09 pm

Since I have managed to shear off the nuts on the downpipe where it connects to the manifold (with very little effort - the studs were not in good shape) I think I have no choice but to remove the entire manifold and replace if I can’t save it. I’m sure it will be tricky and the nuts will be solid.

Be grateful for any tips! Thank you

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Re: Exhaust manifold removal

#2 Post by simon.williams » Sat May 17, 2025 5:12 pm

Like would I be better off grinding the side of the nuts down if possible to do so without damaging the studs..

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Re: Exhaust manifold removal

#3 Post by johnnydog » Sat May 17, 2025 6:43 pm

The manifold to front /down pipe studs were generally prone to seizing / shearing off due to corrosion, especially if steel nuts were used rather than the original brass type.
I have removed many 2000 / 2500 manifolds during my 45 years (:shock:) of owning them, and never had a problem releasing the manifold to head stud nuts.
Sometimes it's worth just trying a very minor (and I mean minor) tightening tweak before attempting to release them - this can just loosen any corrosion on the threads; however, I have never found this necessary.
I've removed manifolds from engines that have been stored outside (although protected from the elements) with no problems, so personally I would be tempted to give it a go. Grinding a slot in the nuts without damaging the studs won't be easy!
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Re: Exhaust manifold removal

#4 Post by Dave B » Sat May 17, 2025 8:14 pm

In my experience over the years, I think you will find that some of the studs will come out with the nuts stuck on them, easily separated when off the head.
As for the downpipe studs, try welding nuts to any stumps that are remaining, and then get the flange as hot as you can before trying to unscrew the studs.
Good luck!
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Re: Exhaust manifold removal

#5 Post by simon.williams » Sat May 17, 2025 8:25 pm

Thank you both

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Re: Exhaust manifold removal

#6 Post by Mike Stevens » Mon Jun 02, 2025 10:07 pm

Hi Simon,

It was good to see your letter in the latest PC!

Good luck with all the work.
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Re: Exhaust manifold removal

#7 Post by simon.williams » Thu Jun 05, 2025 6:45 pm

Thanks Mike. Must have been a slow news month for them!

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Re: Exhaust manifold removal

#8 Post by Binny » Sun Jun 08, 2025 11:26 am

I’ve just removed the exhaust manifolds of both my P.I.s and both came off without issue despite not having been disturbed for more than thirty years.

However removing the three original studs from the down pipe flanges was a different matter. I had to weld an oversize nut on to the studs and managed to remove all but one which snapped flush and had to be carefully drilled until the remains of the stud could be fully removed. Be careful using force as the cast metal of the manifold can fracture without any warning.

Good luck.
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