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Stainless Steel Exhaust Manifold And Galvanic Corrosion


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#1 ac427

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Posted 17 April 2026 - 11:53 AM

The LCB on my car is possibly the wrong diameter for the RC40 exhaust. The manifold is also in a bit of a crusty state after the 30 thirty years.

 

I was thinking of getting a nice stainless steel LCB manifold from Mini Spares. Could corrosion be an issue where the stainless steel would meet the normal steel?



#2 Quinlan minor

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Posted 17 April 2026 - 11:56 AM

Cracking and increased noise in the cabin are the main disadvantages of stainless manifolds, IMO.



#3 nicklouse

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Posted 17 April 2026 - 12:40 PM

Not a fan of the stainless manifolds. If you do get one do not wrap it.

 

yes galvanic corrosion will happen where the two steels actualy touch and have something to act as a conductor.

 

would I worry? Nope.



#4 Ethel

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Posted 17 April 2026 - 01:34 PM

Stainless is a bugger for work hardening, it cracking through fatigue would be a bigger concern. There's so little metal to metal contact I don't think I'd be that worried about galvanic rot. If you go for it, a flexible joint and brackets to encourage any flexion to it would be sensible.



#5 imack

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Posted 17 April 2026 - 02:46 PM

Personally I'd stick with mild steel. My Maniflow 3:1 is 35 years old and still going strong. It'll probably out last me.

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#6 TristanMini

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Posted 04 June 2026 - 01:28 AM

In theory, galvanic corrosion can occur when stainless and mild steel are joined together, but on an exhaust system it's usually not a major concern. Most people run stainless LCBs with RC40 systems without issues. I'd be more concerned about getting the correct pipe diameter and a good sealing joint.



#7 stuart bowes

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Posted 04 June 2026 - 09:51 AM

To some extent the paste will isolate the two pieces from one another anyway, or the gasket, depending on the type of join

 

exhausts in general just rot and stick together anyway being bare metal (of any type) they're always a bugger to get off .  doesn't help that you're trying to do it upside down in a cramped space as well.  fun and games



#8 coopertaz

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Posted 05 June 2026 - 09:38 AM

had stainless lcb for years did worry when i got it about cracking but no issues, just make sure, like any lcb, that it is secure to the diff casing bracket. would also recommend the stainless rc40 (used to be called rc50) and use flat clamps for manifold connections not u bolts then no problem with exhaust rusting on.



#9 andyapanel

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Posted 05 June 2026 - 11:36 AM

I have run a stainless Cooper manifold for several years as the standard ones seemed to rust through every few years. I am very satisfied with it and do not notice a harsh noise.

My only concern is the office at Maniflow who would not reply to queries about the exhaust system support kit I had bought. Their exhausts are excellent.



#10 Midas Mk1

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Posted 05 June 2026 - 12:04 PM

Only LCB's that have ever fitted nice for me are Maniflow ones, and I've fitted a good few to Minis, personally thats the way i'd go.

In terms of stainless cracking, normal mild steel LCB's eventually crack at the join of branches 1/3, even with additional steadies. 






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