300bhp/ton
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Bit harsh maybe?
Disco 2 Exhaust Headers
- Thread starter Richard Askew
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300bhp/ton
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JLR are pretty unhelpful even if you've just spanked £80k on a new vehicle with them. I bet an entire crate of Guiness that they will not give 2 chuffs about a question that is concerned with aftermarket modifications on a defunct model.Bit of a long shot i know but sometimes manufacturers can be very helpful. I used to find this with Ford in days past. So you could try ringing LR and asking them about this question.
Failing that, it depends on how handy you are with a welder etc.
You could fabricate your own headers, it isn't all that difficult and these sorts of people will provide you with the raw materials, https://dir.indiamart.com/impcat/automotive-exhaust-parts.html
But I wonder if you might not be quite happy with just changing the exhaust system without changing the headers. If the ehaders were the be all and end all of an improved system, they would all be making them.
300bhp/ton
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A sports exahust will alter the sound, but do almost nothing for power if you were to put it on a dyno.
Henry_b
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The cylinder heads changed slightly, they went from 14 bolt for the 3.5 to 10 bolt in around 1994 and in 1998 for the introduction of the Thor V8 the castings changed slightly again, not that that is of any of your concern the manifolds would fit,.
The main issue I can see is where is the header collector going to go?
The only disco do get the 3.5 was the D1 and it is a very different design chassis /inner arch wise so you'll find they fit on the engine but won't fit on the car lol..
300bhp/ton
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If it is these: https://www.hedman.com/product-detail/39800
Then I'd say, yes they look like a worthwhile mod. With an n/a engine what you actually want to promote is a thing called exhaust scavenging. Unless you are making 400-500hp it really isn't about flow. Long tube headers are the only type of manifold that will promote exhaust scavenging.
I reckon they should fit, but a 70-74 RR would have used a different gearbox/bellhousing, so there might be some clearance issues. Also a D2 chassis is not the same. But hopefully they can be made to fit. Long tube headers should make enough difference that you might need to get the engine mapped/tuned though. They will alter the fuelling. It'll probably run ok if not, but you won't be seeing all the gains. A cam swap would really compliment these headers too.
Henry_b
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A generic sports exhaust that is the same diameter as the outgoing unit, the only difference being missing mufflers would probably do nothing..
But a mandrel bent 2.5 to 3 inch exhaust with a proper set of cats would improve power along with a set of headers..
Only issue being on a D2 I doubt you'd notice any great improvement unless you added a Cam..
And then you might as well port the heads, then while your there you might as well fit go down the big valve route...
Then you can Tornado map it...
etc etc etc etc...
Don't see the point of a set of uber expensive headers on a 2 ton 4x4..
There is so much science/math that goes into an exhaust.
As OP is just after SS headers they would do the job. May need slight adjustment for chassis clearance but its a good base to start with aslong as he has a mech who can do slight mods.
But as a blanket statement " Long tube headers are the only type of manifold that will promote exhaust scavenging." is a bit broad and misleading. Should really at least start with equal length then work on length and dia as per engine characteristic's/use
J
300bhp/ton
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So we are in agreement that a sports exhaust on it's own is probably worth in the region of 0-0.5bhp gain
300bhp/ton
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Not at all. Firstly these headers are not stainless steel, so completely fail to fulfil that expectation.There is so much science/math that goes into an exhaust.
As OP is just after SS headers they would do the job. May need slight adjustment for chassis clearance but its a good base to start with aslong as he has a mech who can do slight mods.
But as a blanket statement " Long tube headers are the only type of manifold that will promote exhaust scavenging." is a bit broad and misleading. Should really at least start with equal length then work on length and dia as per engine characteristic's/use
J
Plus equal length headers means almost nothing.... equal to what for instance? Equal length means diddly squat in real terms and will not promote exhaust scavenging on its own.
Exhaust scavenging is about harnessing the exhaust pressure wave from one cylinder and using it to help draw air into another cylinder where the intake vale is currently open. This indeed does take science, because you need to have an exhaust that will do this. However short tube headers won't promote this kind of effect at revs lower than about 8000rpm. Which is frankly useless in a road going OHV V8 and barely usable on even a screaming DOHC 4 pot engine.
Long tube headers by contrast will promote exhaust scavenging at much lower rpms. And will therefore offer the biggest n/a gains. If you engine is boosted (turbo/supercharger), then it is a different game entirely, as the air intake is already above 1 atmosphere of pressure and exhaust scavenging will not be taking place.
On a traditional V8 you won't get a perfect system, due to the un-even firing order. Therefore you will have the intake valves open on the wrong bank for the pressure wave at some point during the cycle. With enough pipe work you can solve it, but is impractical on most installations.
Further downstream, the Y/H/X pipe is also performing the role of scavenging. Although between the banks, more than on an individual cylinder.
Unless you are making big bhp, the exhaust gas flow in cfm is unlikely to be all that restricted in most aftermarket exhaust. Not to the extent that you'll see radical power differences at any rate. Many stock systems are more restrictive, but on a 182bhp Rover V8, you'll never seem much of difference in this regard alone.
A full exhaust including LT headers and tuning to match, should make a noticeable difference however.
I had a modded 3.5 RV8 (not in a Landy) making 230bhp and 219ft-lb on the dyno.
Not at all. Firstly these headers are not stainless steel, so completely fail to fulfil that expectation.
Well thats a fail then
I just looked a the pic.J
Not at all. Firstly these headers are not stainless steel, so completely fail to fulfil that expectation.
Plus equal length headers means almost nothing.... equal to what for instance? Equal length means diddly squat in real terms and will not promote exhaust scavenging on its own.
Exhaust scavenging is about harnessing the exhaust pressure wave from one cylinder and using it to help draw air into another cylinder where the intake vale is currently open. This indeed does take science, because you need to have an exhaust that will do this. However short tube headers won't promote this kind of effect at revs lower than about 8000rpm. Which is frankly useless in a road going OHV V8 and barely usable on even a screaming DOHC 4 pot engine.
Long tube headers by contrast will promote exhaust scavenging at much lower rpms. And will therefore offer the biggest n/a gains. If you engine is boosted (turbo/supercharger), then it is a different game entirely, as the air intake is already above 1 atmosphere of pressure and exhaust scavenging will not be taking place.
On a traditional V8 you won't get a perfect system, due to the un-even firing order. Therefore you will have the intake valves open on the wrong bank for the pressure wave at some point during the cycle. With enough pipe work you can solve it, but is impractical on most installations.
Further downstream, the Y/H/X pipe is also performing the role of scavenging. Although between the banks, more than on an individual cylinder.
Unless you are making big bhp, the exhaust gas flow in cfm is unlikely to be all that restricted in most aftermarket exhaust. Not to the extent that you'll see radical power differences at any rate. Many stock systems are more restrictive, but on a 182bhp Rover V8, you'll never seem much of difference in this regard alone.
A full exhaust including LT headers and tuning to match, should make a noticeable difference however.
I had a modded 3.5 RV8 (not in a Landy) making 230bhp and 219ft-lb on the dyno.
I know exactly what goes into designing an exhaust (but it was long ago) Trying to discuss this on a thread where the OP is only after headers that fit (in SS
) Is not really any need. Boosted exhaust are easy "get it out of there"But i still standby my statement that EQUAL length should be a starting point. Different length/size primaries make a huge diff depending on what you want
J
ronsealdeath
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This is all explained quite well on Engine Masters. Always a good watch although most episodes now behind a paywall. I think the exhaust episode is on youtube though.
If you go for headers make sure you wrap them, I had terrible overheating problems with a 3.5 RR turned out that radiated heat from individual pipes overheated block. The cooling system was all brand new so it wasn't to do with that. I refitted original cast manifolds and no more problems so sold 8 branch as it didn't make a great deal of difference. I had fitted 4barrel holley on edelbrock manifold and sports exhaust.
Richard Askew
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My mechanic discussed wrapping them yesterday with me so that is what we are going to do.
