Yes .. i started with a 34ich that causes me a lot of trouble.
Then i found a dmtl from a 2.5 defender and things went better , but still some trouble when the moisture is high . This winter i 've put an aluminum pipe beetween the airbox intake (90/110/Range dry airbox) and the exhaust manifold , now she goes better than ever ..

Oh Yes - I still get occasional problems with the 34ICH- so your solution to the exhaust is bigger is better- did you use any maths to locate the position of the first expansion point- (the first box)? or did you just put them where they fitted best?

ciderman said:

Oh Yes - I still get occasional problems with the 34ICH- so your solution to the exhaust is bigger is better- did you use any maths to locate the position of the first expansion point- (the first box)? or did you just put them where they fitted best?

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LOL the second ... i did'nt any calculation but i eat engines and drink petrol : lol in my experience a 2300/2500cc 100 hp + o - must have an ehaust pipe at least of 50-55mm , the more long is better for torque , two absorption silencers to have a good noise reduction at low speeds and at idle , with a good flow and even better exhaust sound . in fact, now it is very satisfying , while remaining discreet in slow driving. . At some point i realized that my spanish "gordoverdrive" and the 55mm pipe culdn't stay in the same place , so i 've gently sqeezed the pipe in an oval shape for a good 30cm long . This counterpressure caused a new strange rattling noise at idle and very low speed , that can remember the citroen ax exhaust note , and a further increase in low speeds torqe !

As has already been mentioned, a well designed exhaust works on a scavenging effect as the pulses from each cylinder work through. What seems to be missing is the importance of how long the primary pipes are and in what order they combine otherwise the cylinders can interfere with each other. Very few older production vehicles (and particularly Land Rovers) do anything with the exhausts except try to get the waste gas and heat out of the engine bay whilst often being tuned to keep noise and irritating vibrations low, so in theory there is plenty of power to be found. However, get it wrong and you'll get noise, more noise, lots of noise, and maybe less useful power (a torque vs horsepower trade-off).

Having said that, the best power gains are always to be found in removing restrictions and sharp angles in the manifold as has already been alluded to. Be careful not to increase potential heat transfer though, particularly near the footwells.

Personally I now spend a lot of time with text books and Bernoulli before I start looking at how to keep the exhaust as bend free as possible. The problem with this is that by removing the restrictions and improving the flow you always end up with more noise which in an uninsulated metal box of a series might become intolerable.

Seems it's made by Ashley
Part ALRM 30 Used to make these in Stainless. ACR make one too.

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My Perkins has a truly terrible exhaust manifold - 3 right angle welded bends. Now its coming to the end of its life, its a fabrication and its getting thin. I've now seen a neat 2 branch home made one on a web picture. I've printed it off and I'm planning to take it to a local exhaust farbicators. They have laser cutting kit for the flange. I've no idea what the price will be but it could pay for itself as my plan is to make it to mate with the standard Series downpipe. At the moment the down pipe is a special and it too is on its last legs and is sure to cost a lot to replace.

I've had several goes at this, I started with an ACR manifold, but the fit was very poor. Not any more I'm afraid but back then I had more money than time, thus I paid others to fit. By the time I'd worked out what was going on, under stress, the ACR system was ruined. I then spent much the same again trying to sort the issues with custom link pipes. This worked for a few months, then the ACR pipe finally gave in. The ACR is mild-steel thus I should have known better. My total bill must be £1400 plus 3-4 days messing about putting stuff on and off. It's not easy to get the 'fit' right, I've now got a stock 2.5 cast-iron exhaust manifold with ACR heated inlet & SU etc on there. It's a common problem, even stock S3 pipes, going to stock manifolds, ordered from the usual culprits don't fit. Ask me how I know.

Ashley (https://www.ashleycompetitionexhausts.com/manifolds.html) have just about the poorest reputation possible, go on the classic Ford sites and there's not a good word spoken. It has to be said, many come across with very unrealistic ideas of what 'low-production run' systems cost. Getting something to fit, which works, is going to take skill and R&D. Or, custom one-off works, and none of this will be cheap. The Ford crowd seem to think this costs no more than £300? Impossible. That's less than the labour bill. My problem is that I'm willing to pay, but still can't get stuff to fit. As shown by AlfaRomeoman it seems you'll be doing the job twice with anything Ashley. And a third time when it rots, because it's not stainless.

£300-400 is not realistic, you're asking for tosh. And ACR's system does work, producing low power, but won't fit either. In short, I've been down this road, and spent decent time and money. I've yet to find something that fits, works, and lasts.I want a S/S set-up. I have to report, it's not out there. Sorry.

I got prices for my one off Perkins manifold and really got the impression no one wanted to do it, they were making too much money doing Porsches and Ferraris. I've been looking at the component prices and they are very reasonable, £5-£10 per bend so I think I could build a manifold for around £200 compared to quotes of £2000. That's with gasless SS mig wire. I've found a local laser cutters who could make the flange. Its a job for next summer but my conclusion is its very viable to make it yourself.

Obviously a few inquiring minds have gnawed at this problem for a while but it seems like there is no commercial off the shelf (cots) solution to this- I suffer from an ACR manifold which fouls the chassis and prevents the spring shackle nut been fitted. also it is so pitted - it must fail soon and i would like to find a cots item.

Yes, my ACR item fouled there too, and on the gearbox mount. It's a difficult item to make, yours will require a different fit to mine etc etc.. I can't knock ACR minded to the issues. You can see why there's not much choice in off-the-shelf. There's no money in it, how many would anyone be expected to sell? And be it LR or Ford owners, few want to pay for such a thing. As a business-proposition, until you can find 30-40 buyers, the price can't be down at levels most want to pay. A one-off has to be £1500-2000 at a minimum, and that might be too cheap, and too much of a headache. It's a Catch-22.

Hence better to charge a Ferrari owner, stick him on for £7-8000 and be paid for the same headache, this over a small production-run to find 20-30 penny-pinching LR owners. Wheras an LR owner will truly believe £300 is a lot, when it's likely thru' no fault of any supplier, because they've not been paid to custom-fit on a ramp, one or two won't fit. To make it viable, there's a lot of R&D to get ALL to fit. Getting something to fit 30-40 different vehicles is whole heap away from doing one Porsche. And with more 'entitlement' than ever, today's buyers, will refuse to see it.

Our only hope is ACR, they already have their head/cam/2.8/carb etc. Likely to carry on finding buyers for a short-production-run - an improved stainless item of waht they sell now. Can't see it viable for much under say £500-700 and that'd be cheap. Sadly, can't see most able to see it that way, in which case it can't happen. Hence those that do this stuff queue to supply Porsche & Ferrari fanbois, not us.

SpringDon said:

It's more complicated than just bore size due to the fact that exhaust is not a flow but a series of pulses. So exhausts are designed so that bore restrictions reflect pressure that are timed to arrive at the valve at the right time to improve scavenging. But that only works at specific revs and at other Rev ranges can actually make it worse (megaphonitis). This is why cam timing is linked to exhaust design.

Having said that, I've no idea whether that's ever been applied to older landrover engines.

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You won't get much if any scavenging on any log style exhaust manifold. It'll be more about back pressure and A/F ratio. With a Land Rover they would have been promoting low end grunt, not high end revs.

rob1miles said:

My Perkins has a truly terrible exhaust manifold - 3 right angle welded bends. Now its coming to the end of its life, its a fabrication and its getting thin. .....At the moment the down pipe is a special and it too is on its last legs and is sure to cost a lot to replace.

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You've the same issue. Sounds like you're very aware of this, to be done right, unless you can find 4-5 others wanting the same thing, that comes very pricey. Which is why it was bodged in the past. That's always the issue with engine-swaps, "It'll just drop in mate!" It's the one-off add-ons, their time, and their cost that gets forgotten.