The V8 Owners Forum -

Hi

I was wondering if there were any gains to be had by working the original cast headers on my 3.9 disco? I'm stuck at the moment with stock setup, partly due to cost, partly due to to having to keep the cats. Is it worth opening up the headers at the flange face a little to create a reversion step? (I have used this mod to good effect on other engines in a higher state of tune) and I was thinking of replacing the original center muffler with a straight through one.

Any thoughts?

Brian

I would at least make sure there isn't a 'reversion step' facing inwards towards the valves!, the tolerances are pretty poor on the head to manifold interface.

Chris.

Hi Chris

The line up on the manifolds can be THAT BAD! lol O.k. will deffo take a look at them now. I will replace them later with some 4-2-1's and a better system, but for now just trying to get the best out of every penny spent!

Disco manifolds should be 4-2-1 anyway?

I thought only the defenders, stage ones and 101's had 4-1 manifolds....

sorry, I meant 'tuned tubular 4-2-1' manfolds and a better system

ah- gotcha!

I'd have thought the middle one is easy to work on, its the pesky rear one that needs getting out of the way?

Good studs are your first step in getting the cast manifolds to align, be very careful as 2/3 I have here had the flange bolt holes opened up to fit so they could be all over the place... For the Disco I just use 4 good studs per bank & the rest cheap socket set screws, but I have tubular manifolds on it now & did away with the heat shield added extension bits..

The bends are so tight in the cast manifolds take note where to put any step due to the shaping of the flow.