Defender V8 - fitting 3.9 exhaust manifolds

[camel_landy]

CAPP0 said:

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).

Don't rule out the induction noise as it can be very pronounced when under load (as I found out when I fitted a raised air intake to a RR Classic).

M

[Ranger 6]

Funnily enough I stripped the system off the other week as the V8 downpipe to system joint was leaking.

Now waiting for the clutch to start slipping as the pedal is really high.

[CAPP0]

100SRV said:

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

I’ll have to check that, I don’t know. It’s got a bog standard TD5 exhaust system on there, with the centre silencer the size of a London bus. Thing is, it was doing this with the Jetex custom exhaust and changing it hasn’t altered anything at all.

camel_landy said:

Don't rule out the induction noise as it can be very pronounced when under load (as I found out when I fitted a raised air intake to a RR Classic).

M

I’m definitely leaning towards it being related to that now. Removing the cone filter made no difference. If you have your head under the bonnet on tickover, there is what I can only describe as an occasional “mooing” coming from the intake area. This has the 90 degree rubber (?) intake pipe on it - can those break down? I have a vague recollection of reading that they can/do? Might that be the source?

The only other thing that I can (unhelpfully) add is that when I bought the donor, it was MOTd and running and I drove it home and didn’t experience any of this. I don’t think I would be able to wedge the original air filter in, even temporarily (and I also have a feeling I binned it anyway) but I can’t think how else to test it?

[camel_landy]

CAPP0 said:

camel_landy said:

Don't rule out the induction noise as it can be very pronounced when under load (as I found out when I fitted a raised air intake to a RR Classic).

I’m definitely leaning towards it being related to that now. Removing the cone filter made no difference. If you have your head under the bonnet on tickover, there is what I can only describe as an occasional “mooing” coming from the intake area. This has the 90 degree rubber (?) intake pipe on it - can those break down? I have a vague recollection of reading that they can/do? Might that be the source?

The only other thing that I can (unhelpfully) add is that when I bought the donor, it was MOTd and running and I drove it home and didn’t experience any of this. I don’t think I would be able to wedge the original air filter in, even temporarily (and I also have a feeling I binned it anyway) but I can’t think how else to test it?

You could try taking the bonnet off and jerry-rig something?

As for the rubber intake, it's not unknown for that sort of thing to lose its structural integrity and start to collapse under load. However, you'd probably also notice a lack of power as it would starve the engine of oxygen.

M

[CAPP0]

camel_landy said:

CAPP0 said:

camel_landy said:

Don't rule out the induction noise as it can be very pronounced when under load (as I found out when I fitted a raised air intake to a RR Classic).

I’m definitely leaning towards it being related to that now. Removing the cone filter made no difference. If you have your head under the bonnet on tickover, there is what I can only describe as an occasional “mooing” coming from the intake area. This has the 90 degree rubber (?) intake pipe on it - can those break down? I have a vague recollection of reading that they can/do? Might that be the source?

The only other thing that I can (unhelpfully) add is that when I bought the donor, it was MOTd and running and I drove it home and didn’t experience any of this. I don’t think I would be able to wedge the original air filter in, even temporarily (and I also have a feeling I binned it anyway) but I can’t think how else to test it?

You could try taking the bonnet off and jerry-rig something?

As for the rubber intake, it's not unknown for that sort of thing to lose its structural integrity and start to collapse under load. However, you'd probably also notice a lack of power as it would starve the engine of oxygen.

M

Can't be collapsing then, the engine is still very perky, although I guess there could be an air leak somewhere. Do you know what the correct name for that part (the intake pipe) is so that I can search one out to try? I've hunted eBay with no luck so far.

[camel_landy]

CAPP0 said:

Do you know what the correct name for that part (the intake pipe) is so that I can search one out to try?

Pass...

FWIW - It might be worth trying to see if you can get hold of a parts list / diagram for the Defender 50th or the NAS, as that will probably have what you need.

M

[CAPP0]

Thanks, good call, I'll look into that.