Morris Minor Owners Club

Why are exhaust manifolds always so rusted? Must be the extreme heat. Does manifold paint really work?
Thanks
Dave

Because of the heat/cold cycle - and unpainted metal be it cast iron or steel. Stainless don't 'rust' - but do dis-colour. And yes - proper high temperature paint correctly applied does work!

How about proper prep for paint? Do we like brush-on or spray can?
Obviously wire brush all rust and scale off...
Thanks!

I have shot blasted my Cavalier manifold and applied VHT aerosol paint which looked great for a year or so, now it's started to go rusty again. I think the best treatment is ti have it Vitreous Enamelled, I think Jaguar used to do this when you could still se the manifold but might not now that you need to start dismantling things before you even get a glimps!

I've never bothered myself. I've had three MOWOG manifolds and seen many other original items that have surface rust but are solid.
Theres not point painting it other than cosmetic reasons. The continual high heat keeps the rot at bay anyway.

Has anyone seen a rotten cast steel exhaust manifold? IME once some surface rust has built up they don't get any worse.

I've never tried it myself but believe the traditional black polish used for stoves is suitable to smarten up a manifold.
http://www.castironfires.com/detail.asp?id=905
Not a permanent solution, and just like a stove, needs reapplying every so often.

Paul Humphries

I throroughly wire brushed my manifold and then cleaned before giving several coats of matt black VHT paint. Its lasted a good while but there are a few spots of brown where the rust is coming back. I'd reccomend using using the electrlytic rust removal trick (there's a thread on here somewhere) to clean up the manifold before wire brushing and cleaning. Its lasted perfectly on my brothers car. I just wish I'd done the same.