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Discovery V8 Cat downpipe differences?


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A little while ago i posted about the difficulty i was having sealing the manifold to downpipe joint.  It was always blowing out the same place and i can only assume the mating flange on the downpipe is warped.  I initially decided to bite the bullet and buy a new stainless steel downpipe from rimmer bros as i already have a stainless centre and rear section.  Unfortunately, as always seems to be the case, my car would appear to need the more expensive option.  My Discovery is a 1996 with a VA chassis number, which should have ESR3730:


However, ESR3063 is much cheaper:


Can anyone tell me what the differences are and whether they're likely to be interchangeable.  I should probably say, I'm fairly sure it actually currently has a downpipe from an earlier car on it anyway but i can't be sure of it's age because it came from a breaker I know but he was fairly confident it was off a late Range Rover classic, he says he's never broken a V8 Discovery.  He allowed me to take it away and return it if it didn't fit but it was identical to the original.



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Can't you have the warped face ground or milled flat ? There is plenty of material there,new gaskets,studs and nuts should seal it. If there is a crack where the flange is welded to the downpipe it can be welded very successfully using mild steel wire in an ordinary Mig welder.

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Earlier this year I had the Double S tubular manifolds off my RRC.

The state of the manifold to gasket face was shocking to say the least, badly pitted & areas of up to 1cm in length corroded away. The cylinder heads were entirely unaffected.

I did contemplate junking them but I don't like giving up & refaced them with 40 & 80 grit emery on a steel block. Took a while but got to the point where a new gasket & a smear of firegum on the pipes did the job, so might be worth the OP trying something similar.

Or find a local engineering company & get them to do it for you.

BTW leaks from an exhaust manifold can sound exactly the same as a faulty tappet so worth checking before stripping the engine.

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Thanks for the replies.  I did notice the slight change in length after the 2 pipes join but i wondered if the overall length was the same, obviously not, that's a shame.

I probably could get the mating face machined but i was hoping to minimise the time the downpipe was off the car and i did fancy a stainless downpipe to go with the rest of the system. I didn't think £270 was out of the way for a pair of cats but i don't want to spend near double that.

I have standard cast manifolds, i've changed the manifold to head gaskets for composite type ones with fire rings, i'm confident there's no leak there, every time i take the downpipe off, the right hand gasket has a witness mark where it's been blowing.  The noise is 100% from the exhaust.

I'll see what i've got to do this weekend but with any luck i might try and get the downpipe off again and see if i can sand it flat.

Thanks again


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