Defender V8 - fitting 3.9 exhaust manifolds

[Ranger 6]

I've got some 3.9 manifolds for my 90 V8.

The 3.9 downpipes/Y pipe appear to go straight into the crossmember, however the 3.5 efi parts would seem to go over the crossmember.

Any thoughts on what's the best solution?

[100SRV]

Build one with Jetex parts? My Downpipes have been on since I fitted the 3.9 some eighteen years ago so the effort won't be wasted. Also you can build a better two to one transition than factory parts.

[300bhp/ton]

The RV8 responds well to long tube style tubular manifolds (IMO). If you could fab up something it would be worthwhile.

Using any of the factory log style manifolds are all going to be pretty much the same in performance terms. So if not going for performance, go with what fits the best and/or easiest.

Edited by 300bhp/ton on Sunday 8th March 11:35

[CAPP0]

If you want to use them you need a Disco 1 V8 x-member. I have them on mine, including the cats, they fit fine. The Disco x-member is kinked up at each side. I can try and take a pic later if that helps.

Edited by CAPP0 on Sunday 8th March 15:28

[Olas]

with your chosen manifolds fitted, you'll have to decide which route you want the exhaust to take.

If the only issue is the cross member then buy some bends and some straights off ebay, and get under the car. it's effectively a jogsaw, but if you only have one obstacle then a selection of 45degree bends should see you right.

is it possible to bodge the 3.5 Y onto the 3.9 manifolds? if not you need to order some 45 bends.

[CAPP0]

Olas said:

with your chosen manifolds fitted, you'll have to decide which route you want the exhaust to take.

If the only issue is the cross member then buy some bends and some straights off ebay, and get under the car. it's effectively a jogsaw, but if you only have one obstacle then a selection of 45degree bends should see you right.

is it possible to bodge the 3.5 Y onto the 3.9 manifolds? if not you need to order some 45 bends.

Depends on where the manifolds came from but it's unlikely to be as simple as that. See below, this is my 90 with Disco 1 manifolds/Y piece (all in one) with the cats still in place. If the manifolds you have have the cats on, and you wanted to keep the existing x-member you would have to cut the cats out, there's zero space after them to be adding extra pipework. As above, this is the Disco x-member, you can see how it kinks up at each side whereas the original 90 one is straight right through and that's why the OP can see that it interferes with the manifolds/y-piece.






I can't imagine it would be difficult to get a Disco x-member and the chassis rails are the same distance apart so its a straight swap.

Here you go:

Third from the right is the one you need.

Edited by CAPP0 on Monday 9th March 06:57

[Ranger 6]

Thanks, that’s the pipes I’ve got

It was this RRC 3.5 EFI that made me think it’s an alternative.

[CAPP0]

Ranger 6 said:

Thanks, that’s the pipes I’ve got

It was this RRC 3.5 EFI that made me think it’s an alternative.

I had a 3.5 in mine previously (now 3.9) and yes, the headers were similar to your pic. They are a much smaller diameter tho, and also they have those slip joints onto the Y piece which wear and are a bugger to seal up, which the Disco ones don't have. The output flange/diameter on the 3.9 headers is (iirc) 2.5". I had exactly the same thought when I installed the headers onto my 3.9 until I remembered that the Disco x-member is different. Although they are only cast manifolds, I'm sure I once read somewhere that the Disco headers do flow the exhaust gases quite well.

[Ranger 6]

Interesting - I'd prefer the larger bore pipes to enhance the noise (and power?)

I've managed to win a TD5 exhaust on eBay quite reasonably so will see if I can join the pipes I've got. I'm watching for a crossmember so the whole;e thing is coming together slowly.

[Ranger 6]

I've now got the fanny-molds, the downpipes, system and D1 cross member. The next stage is all the nuts, bolts and sundries to actually fit all this. There will be some extra welding to get the cross member to fit.

[Ranger 6]

After some time here's a lockdown update.....

It's all on - the last piece is going to be the hanger for the middle box which will be the last piece.

There was a bit of fettling to be done to get it to fit properly.



The final piece has been to fit some new needles so the engine breathes properly. After some considerable online research I chose BBW. With a check on mintylamb's tool http://www.mintylamb.co.uk/suneedle/ the comparison with the standard BGC suggested the should be an improvement. The other suggestion I looked at was BDR (100SRV on another thread), but that looked a bit rich at the top end.



From a run round the block just to check things it really does seem to have transformed the car. The deeper breathing enabled by the manifolds has given the car greater 'legs'. It pulls now in fifth gear, which used to be just a breathless overdrive and low rev pickup has been improved with the needle change.

The next step is to get the timing/mixture etc checked...... and all the other maintenance that a 33 year old Land Rover needs

[CAPP0]

Ranger 6 said:

I've now got the fanny-molds, the downpipes, system and D1 cross member. The next stage is all the nuts, bolts and sundries to actually fit all this. There will be some extra welding to get the cross member to fit.

Can I just confirm there, you have Disco 3.9 manifolds and a TD5 exhaust from the cats/flange backwards? And it fits? What diameter is the TD5 system?

I did what 100SRV above did and built a system from Jetex parts, I have messed around with silencers etc but whilst it sounds good when you start it, the buzzing and droning at motorway speed is really starting to grate on me (plus I can't hear any other ominous noises if I need to!). My next step was to order a TD5 system as it looks like that might go straight on? I can experiment with the front silencer delete afterwards.

The TD5 front silencer has a 2-bolt flange, I believe? To mate to the headers, assuming the sizing is in fact correct?

Edited by CAPP0 on Sunday 7th March 14:12

[Ranger 6]

Basically yes, the manifolds are 3.9 either RRC or disco. The down pipes are RRC not discovery and no cats. Then the system is a TD5. The joint to the down pipes is the two bolt connection as the picture. I can take more photos if it would help.

The down pipe to system joint isn’t perfect and needed some tweaking. The hangers and cross member also need ‘adjusting’.

The sound is good, light throttle/cruising is quiet and when you’re pushing on it’s nicely ‘throaty’ without being excessive.

Drop me a PM as I think you may be close enough to meet (I’m in Surrey) I’ve got a 3.9 which is in pieces ready for crack testing etc before a rebuild.

[100SRV]

CAPP0 said:

Ranger 6 said:

I've now got the fanny-molds, the downpipes, system and D1 cross member. The next stage is all the nuts, bolts and sundries to actually fit all this. There will be some extra welding to get the cross member to fit.

Can I just confirm there, you have Disco 3.9 manifolds and a TD5 exhaust from the cats/flange backwards? And it fits? What diameter is the TD5 system?

I did what 100SRV above did and built a system from Jetex parts, I have messed around with silencers etc but whilst it sounds good when you start it, the buzzing and droning at motorway speed is really starting to grate on me (plus I can't hear any other ominous noises if I need to!). My next step was to order a TD5 system as it looks like that might go straight on? I can experiment with the front silencer delete afterwards.

The TD5 front silencer has a 2-bolt flange, I believe? To mate to the headers, assuming the sizing is in fact correct?

Edited by CAPP0 on Sunday 7th March 14:12

Use Jetex silencers too. I have no annoying droning or buzzing noises on my 100" which uses 3.9 Manifolds, downpipes then all 2.5" Jetex parts. Oval silencer in the middle and cylindrical one near the tailpipe.

[CAPP0]

100SRV said:

Use Jetex silencers too. I have no annoying droning or buzzing noises on my 100" which uses 3.9 Manifolds, downpipes then all 2.5" Jetex parts. Oval silencer in the middle and cylindrical one near the tailpipe.

Interestingly that's exactly what I have, as we discussed before. I remember you kindly sent me picture of the underside of yours. I've also experimented with deleting the rear cylindrical one, but there's a constant droning buzz, which feels like it's at the front, probably the front silencer, and having used the car on the motorway several times recently, it's really wearing after a while. I'm sure it's the exhaust, it stops instantly when you lift off the accelerator, and only does it under load, and varies with the pedal too.

[100SRV]

CAPP0 said:

Interestingly that's exactly what I have, as we discussed before. I remember you kindly sent me picture of the underside of yours. I've also experimented with deleting the rear cylindrical one, but there's a constant droning buzz, which feels like it's at the front, probably the front silencer, and having used the car on the motorway several times recently, it's really wearing after a while. I'm sure it's the exhaust, it stops instantly when you lift off the accelerator, and only does it under load, and varies with the pedal too.

Sounds like mounting transmitted noise rather than it emanating from the actual system, i.e. vibration rather than accoustic. What mountings did you use? I have used Range-Rover classic mounts (572166 and related) having one at the either end of the centre silencer and one at either side of the rear silencer.

[CAPP0]

100SRV said:

Sounds like mounting transmitted noise rather than it emanating from the actual system, i.e. vibration rather than accoustic. What mountings did you use? I have used Range-Rover classic mounts (572166 and related) having one at the either end of the centre silencer and one at either side of the rear silencer.

That's an interesting thought. At the rear I have a couple of the ones with the clamp and metal strap joined by a rubber strip, and at the back of the front silencer I added a bracket to the silencer so that I could use the body mount with a rubber bobbin. I'll mess around with those a little then before committing to changing the whole exhaust!

Also since my last post on this thread I've picked up a little blow on the LH manifold somewhere. Haven't tracked it down yet but that's really annoying as nothing should have moved.

Thanks again for your input 100SRV.

Edited by CAPP0 on Tuesday 9th March 16:35

[CAPP0]

Ranger 6 said:

Drop me a PM as I think you may be close enough to meet (I’m in Surrey) I’ve got a 3.9 which is in pieces ready for crack testing etc before a rebuild.

I'll do that. I'm close to the "other end" of the M26 from you.

[CAPP0]

CAPP0 said:

100SRV said:

Sounds like mounting transmitted noise rather than it emanating from the actual system, i.e. vibration rather than accoustic. What mountings did you use? I have used Range-Rover classic mounts (572166 and related) having one at the either end of the centre silencer and one at either side of the rear silencer.

That's an interesting thought. At the rear I have a couple of the ones with the clamp and metal strap joined by a rubber strip, and at the back of the front silencer I added a bracket to the silencer so that I could use the body mount with a rubber bobbin. I'll mess around with those a little then before committing to changing the whole exhaust!

Also since my last post on this thread I've picked up a little blow on the LH manifold somewhere. Haven't tracked it down yet but that's really annoying as nothing should have moved.

Thanks again for your input 100SRV.

Edited by CAPP0 on Tuesday 9th March 16:35

Just revisiting this one again. I decided to change the exhaust anyway just to rule it out, as it was a cheap option, so I fitted a fully-silenced TD5 system. But, as 100SRV correctly deduced, that's not the issue. The symptoms are, if I accelerate gently, no resonance/booming, if I accelerate hard, then the noise is really quite loud, but as the revs rise, the higher the revs the quieter the noise gets. I might be able to get a sound recording of it, I'll post it up if so. I really don't know what is causing it.

I even wondered about the intake, but that's simply the MAF with a foam cone filter on it (due to space constraints).

The exhaust is all now on rubber mounts, mainly this type:



The cats sit quite close to the chassis rails, but they would have in the donor Disco anyway so it can't be that?

[100SRV]

CAPP0 said:

Just revisiting this one again. I decided to change the exhaust anyway just to rule it out, as it was a cheap option, so I fitted a fully-silenced TD5 system. But, as 100SRV correctly deduced, that's not the issue. The symptoms are, if I accelerate gently, no resonance/booming, if I accelerate hard, then the noise is really quite loud, but as the revs rise, the higher the revs the quieter the noise gets. I might be able to get a sound recording of it, I'll post it up if so. I really don't know what is causing it.

I even wondered about the intake, but that's simply the MAF with a foam cone filter on it (due to space constraints).

The exhaust is all now on rubber mounts, mainly this type:



The cats sit quite close to the chassis rails, but they would have in the donor Disco anyway so it can't be that?

Is the centre silencer equidistant from the tail pipe outlet and engine?
How close is the tail silencer to the tail pipe outlet?