Lucky Breathes Easy

That looks a much better bet than the P6 originals. But I'd still be more comfortable with a conical filter in that space to give acceptable changes of direction in the air flow. Just pop down the local motor shop and try a few K&N's and similar until you can find one that fits. Interesting that for the SD1 Rover acknowkedged the problem with the P6 system.

Chris
 
Hello Barten,

That air cannister is off an early SD1 in the region of circa 1976 - 1977. The reason it is so much larger in terms of the inlet is that air was supplied directly via the exhaust manifolds. That is hot air was taken via ducted pipes from either side of the engine, brought up into a large 't' piece and then attached via a rubber tube onto the end of the air cannister. In effect the engine was breathing nothing but hot air, which is not nearly as efficient in terms of making power as cold air. So the engine would require a lot more air to make the same power as if it were being fed with colder air. For that reason the filters within the air box are larger.

Now it is also my understanding that the aluminium alloy elbows that link the air cannister to the carburettors are actually smaller in cross sectional area than those fitted to the P6B as standard.

If you use that air cannister and fit cone shaped K & N filters within or another brand of filter of similar design, you will need to fit richer needles. With HIF6 carburettors,..BAK or slightly richer BAF should see you keeping out of trouble in terms of a lean running engine.

Ron.
 
SydneyRoverP6B said:
That air cannister is off an early SD1 in the region of circa 1976 - 1977. The reason it is so much larger in terms of the inlet is that air was supplied directly via the exhaust manifolds. That is hot air was taken via ducted pipes from either side of the engine, brought up into a large 't' piece and then attached via a rubber tube onto the end of the air cannister. In effect the engine was breathing nothing but hot air, which is not nearly as efficient in terms of making power as cold air. So the engine would require a lot more air to make the same power as if it were being fed with colder air. For that reason the filters within the air box are larger.

Ron.
Click to expand...

It is off an early SD1 but the set up is not as you suggest. On the front of the air cleaner box was a thermostatically controlled flap, one side of which was piped to an exhaust manifold to draw hot air for when the engine was cold, and the other side piped to the front of the car to draw cold air for when the engine was at normal working temperature.
 
Thanks for the Interesting information you guys have. I have never seen the set-up with this filter box in an SD1, and no trace of these ducts/flaps in my car anyway. Tomorrow I will measure the elbows and compare them with the originals I have in the 1971 3500. As for the K&N filters I guess they will be less restrictive and probably a lot easier and cheaper to get hold off here.
Regards, Barten
 
roverengine.jpg
 
harveyp6 wrote,...
It is off an early SD1 but the set up is not as you suggest. On the front of the air cleaner box was a thermostatically controlled flap, one side of which was piped to an exhaust manifold to draw hot air for when the engine was cold, and the other side piped to the front of the car to draw cold air for when the engine was at normal working temperature.
Click to expand...

Arrrr thanks for that Harvey. I based my interpretation on a black and white photo in a book taken from the driver's side, so the destination of the feed drawing air from the front of the car could not be seen, so I assumed incorrectly that it too came up from the exhaust manifold.

The SD1 with that arrangement was never officially imported into Australia as the SU carburettors (the one in your photo has Stombergs) no longer met the emission requirements which had been imposed by the Australian Government. The first SD1s were imported in 1978, and they were fitted with twin Zenith-Stromberg 175 CD carburettors. The air cannister arrangement was completely different with each carburettor having it's own little rectangular air box.

Ron.
 
I've not seen that SD1 arrangement before, was it just for export cars?

Looks like quite a good system though maybe it could be transplanted on to a P6 to get a decent cold air feed instead of sucking in air that's been through the radiator.
 
testrider wrote,...
I've not seen that SD1 arrangement before, was it just for export cars?

Looks like quite a good system though maybe it could be transplanted on to a P6 to get a decent cold air feed instead of sucking in air that's been through the radiator.
Click to expand...

Hello testrider,

According to my Rover SD1 book, that air intake system was fitted to cars produced for the UK market. It certainly was never fitted to cars sold in Australia. As to whether it appeared on SD1s sold to other countries, I cannot say.

Obtaining a direct feed of air at ambient temperature is certainly beneficial in terms of increasing power. The real problem that follows though is if the feed has direct access to a good steam of outside air, it can also have direct access to water when it rains. If a large splash of water is ingested by the engine by what ever means, then the engine will be literally destroyed with bent connecting rods at the very least... :shock: Personally I feel happier with the air intake well inside even at the expense of a few horsepower.

Ron.
 
Hadn't thought about water ingestion Ron, thanks for pointing that out.

Ah well, back to the drawing board.....
 
Hi, that is a long way for the water to go before it gets into the cylinder.
It has to go up a pipe of at least 18" and then opens out into the filter
housing and then through a filter. I think the water would have fallen out
of the air by then and what little remains will aid combustion. Colin
 
And of course, it would be a suitable arrangement for the UK as opposed to Australia, as it never rains here..... :?
 
harveyp6 wrote,...
And of course, it would be a suitable arrangement for the UK as opposed to Australia, as it never rains here.....
Click to expand...

Funny you should mention that Harvey. The average annual rainfall here in Sydney is a touch over 1200mm, whilst in London and much of East Anglia it is no more than 700mm.. :shock: I was very surprised to say the least. The wettest part of England is in the Lakes District which sees on average 3000mm per year. Same with the highlands of Scotland and Snowdonia in Wales. The wettest town in Australia is Tully in far north Queensland which sees on average 4500mm per year.

Ron.
 
I have now measured the elbows, and the SD1 elbows has an outer diameter of 66 mm, vs 72 mm for the original P6 3500 elbows.

regards, Barten
 
Hi Gents

I was interested to read your comments about using an SDI aif filter housing. I too have introduced an SD1 Cylindrical housing (as opposed to the elliptical shape) into my P6 but retained the P6 elbows. My set up looks similar to the car shown in this P6 (photos attached).

The problem I currently have is obtaining the correct air filter spec. All SD1 user manuals and mator factors list a different size filter size which is too long for the filter housing which was donated from a 1977 SD1. They need to be about 160mm in length, otherwise they are visible from the intake mouth.


I found that using the P6 elbows (which may be slightly lomger than the original SD1 elbows) causes the air inlet mouth to point upwards too much requiring the holes at the filter mounting positions to be opened out (into a slot) to allow the filter to be 'rotated' slightly on its mountings.

Any information on the correct filters would be much appreciated.

At present a rolling road awaits to confirm needle sizing.

Regards
Eggbert68b
air_filter_2.jpg

air_filter_1.jpg
 
Hello Eggbert,

The photos that you posted with your above post are of my Rover... :D

The original SD1 filters for that SD1 air cannister are indeed long enough so they can be seen through the inlet. However, with the orignal 't' piece fitted onto the end of the inlet supporting hoses running off to duct hot or cold air as the situation required, it made no difference as the filters could never be seen.

As you will be running the cannister as it appears in the photos of my engine, then the filters that you would like would need to be somewhat shorter. I use K & N filters in mine, but they too can be seen when looking into the inlet. My engine being a 4.6 draws over 30% more air than a 3.5, so they needed to be large enough to supply all the necessary air without being restrictive.

The P6B elbows are indeed longer and as Barten has confirmed, larger in diameter too when compared to SD1 elbows. The air cannister is in fact a smaller diameter when compared to the P6B issue, but the inlet significantly larger thereby allowing almost 3 times the volume of air to enter per minute. Of course the engine won't draw any more air than it needs to, so paper filters in the order of 60mm in height will provide a surface area more than sufficient to meet the flow requirments of the 3.5 litre engine. You can of course choose larger filters without detriment.

Ron.
 
Hi Ron,

It occurred to me just after posting my reply that it was your Rover I was using as the illustration given the Sydney link - I actually discovered your pictures on the V8 Forum which I also review regularly and follow your comments on other V8 related posts. You've got a motor to be proud of there.

My P6 has a 3.9 block and SD1 heads and so initially I strove to draw more air in, however in reality I would expect that the OEM cannister and filters could draw enough air to supply a 3.9. But it looks good and somewhat understated, albeit mine as a daily driver is far from being as pristine as your car (particularly with our weather).

Your comments about the SD1 OEM filter length are interesting as I forgot that the housng assembly included a T piece and the inlet would not be visible. However the filters I currently have do not fit the housing internal mounting bracket whithout using a longer length securing screw. With the filters I sources (which I thought were OEM) there is little clearence between the filter edges and the canister walls (and are much longer than the P6 filters) - was this tight clearence meant to be the case - your comments on the effect of this would be welcome.

From experience I chose not to use the K&N filters given the engine roar which I felt 'droned' somewhat to my taste - hence the preference for the OEM filters.

Cheers
Simon
 
Hello Simon,

With a 3.9 litre engine, the OEM P6B air cannister inlet is borderline at best, but on a hot day with hot air, the inlet would prove to be too small. The OEM P6B filters are too small right from the off to pass the volume of air that your 3.9 would require. So the SD1 cannister with its massive inlet is indeed the ticket for success.

The SD1 with that air cannister was never imported into Australia so it is my understanding, so the air cannister that I have and another I obtained for a friend came off cars that to my knowledge had been private imports or the engine breathing system had been changed once it was here. In any case, the filters that were within the cannisters when I purchased them were the correct length for the brackets within and did indeed run very close to the inside surface of the cannister...not much more than 1cm all round from memory. The filters are more than large enough to meet the flow requirements of your 3.9 when sitting in the open air, so their size when fitted within the cannister given their close proximity to the inside surface would make up for any reduction in access.

From you first post Simon I assume that your engine still has the original needles,..BBV or BBG? Once you have fitted the SD1 cannister and filters, try to limit your driving till you have been to the rolling road as your engine will almost certainly then be running lean, and depending on how severe, damage can result. The rolling road will certainly be the ticket, so either swapping those needles for richer ones or polishing those or a different pair will make such a difference!!

Ron.
 
This is very interesting. The net effect of the revised canister and filters must be very similar to the route I took. Bearing in mind the performance boost I got with a standard 3.5 emphasises how inadequate the original Rover design is.

Chris
 
Hi Ron,

Many thanks for your comments, and point taken about the restriction in use. Currently I do use the standard BBG needles given the SD1 heads (and 3.9 block). I look forward to the rolling road session and plan to spec. the needles for road use and variable rev range rather than for the higher end / speed use. The boy racer days are now replaced by 2 child seats in the back. The last thing I need is to blow the engine on the rolling road.

Would I be right in thinking that for the SD1, the large air intake due to the larger inlet size and filter surface area was compromisd by the restriction in air flow due to the long inlet ducts - otherwise with BBG needles the engine would have been running too lean (even with the smaller 3.5 block).

Once again, thanks for your coments
Regards
Simon
 
Whatever changes are made to an engine will affect the choice of needles. Whether it be valve size, compression ratio, restrictiveness or otherwise of the intake system, back presure of the exhaust etc etc. It is therefore a very brave man who guesses the profile of a needle without seeing that particular engine and ancilliaries on a rolling road. The best that Ron and I and all the web pages in the world can do is to make a stab at a likely solution which will allow your engine to run sufficiently well to tide you over until you see it on the rolling road. Once there don't try and second guess the outcome - you're likey to annoy the guys setting your up engine intensly!

The point of going to a rolling road is to be able to collect data that is not available to you under normal or even expert amateur circumstances. And to be able to do this under loaded conditions. Given this data, it is then possible to devise a new distributor advance curve, and needle profile - not necessarily from within the range sold to the public.

There is actually no need to ask for a particular bias towards racing, torque, fast road etc. Generally - although as with everything in engineering there are exceptions - the highest power / torque (they are the same thing: power = torque X engine speed) will also generate the best economy and responsiveness. The exceptions do though relate to petrol engines, where a fuel air ratio in excess of the stochiometric will generate slightly more power. but this effect is minor. For a diesel the relation is pretty well absolute, which is why the most powerfull diesels are also the most economical.

Ergo - don't spend too much effort choosing a needle to get you started. Concentrate on getting it to the rolling road as quick as possibe. They are surprisingly cheap, and I'm certain you will be astounded by the result. When we did Lucky we raised power at the back wheels from 62 to 112!

In the meantimne, concentrate on giving the engine the best chance to generate power. Free up the induction system, either by the method discussed here recently or by the method I used at the start of this thread. Take steps to reduce the exhaust back pressure. (in English, use a bigger diameter system, an extractor manifold, through flow silencers etc) Use the highest compression ratio you think you can get away with (compression ratio defines the maximum theoretical efficiency of an engine - the higher the more efficient and hence the most powerful). Choose your cam carefully for the character of engine you want - all revs? or all torque? Are the valve seats nicely angled? Have you had a go at cleaning up the inlet tracts? Are the ports of the inlet manifolds and exhaust manifolds properly aligned with the heads? Detail is everything in engine building.

If you need any recommendations for rolling roads that understand the engine, I've successfully used a place in the Cotswolds and Quattro has had good experiences with a place in Blackpool.

Best of luck

Chris
 
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