Jaguar Mark IV Air Cleaner Filter

Hello Everyone,

I’m thinking about replacing my current air cleaner filter set which currently looks:

with original air filter cleaner which I will have to restore.

I’ve recently came across these two air filter cleaners - they seem to be from Mark V but they differ from each other:

Which one is the right one?

I do know that I would have to acquire another part:

Do You know the source for this part?


First off, there were three different air cleaners for Mark V.
The 2.5 Litre used C.1808 (AC1579005).
The 3.5 Litre first used C.2594 (AC.3755) and later C.4507 (AC.3873).

Your second filter, the one missing the mesh, appears to be the same as mine for my 3.5 Litre, but I don’t know which mine is. It looks like they took a short one and made it a bit longer by adding a section, so maybe this might be the difference? Is one of yours longer?
Here is mine:

The part you need is called Air Intake Pipe. Some people call it a plenum.
The 2.5 Litre used C.2817 and the 3.5 Litre used C.2818.
I imagine the difference is how they fit with the H3 carbs vs the H4 carbs, and possibly the inlet diameter to fit the different air cleaners.

Here is mine for my 3.5 Litre:

Notice the angle on the bottom rear corner. This is to clear the steering column on LHD Mark V. These things collect oil from the rocker cover breather so there is a tiny drain hole in the bottom.

The Mark IV parts book lists air cleaner pipes C.1789 and C.1790 for both RHD and LHD cars. I wonder is that a mistake, or did they make a further change for Mark V?

Finally, as you are shopping the used parts market, be sure not to buy one for a Mark VII, as they will not fit. The carbs center to center spacing is different.
Here is one for a Mark VII:

Notice the extra breather holes for the H6 carbs.

There are at least two silencers typically found on Mark V cars (which are similar to what you picture). One has a feed hole from the rocker cover and one does not. While some places refer to these as cleaners and silencers, my impression is the only cleaning these do is to prevent boulders and birds from entering the engine. However, they do a great job at reducing the high frequency carb air hiss heard when inside the car. These were called the “Sphinx” model by A.C., presumably to emphasize that the carbs appear unheard when used.

The manifold (also called a plenum, among other names) from the silencer to the carbs can be sourced via eBay or similar, with some patience. These manifolds vary with model, as do the silencers (there were several similar silencer varieties in use on other cars, not just on Mark V cars), so use care to find the one which will work for your purposes. Also, it has been my experience gathering a few of these manifolds for Mark V cars that the manifolds have significant variations in their dimensions and bolt positions. Maybe there is some variation for RHD and LHD? They seem to have been chosen or fettled to the car, similar to individual fitment of the rear wheel spats.

Two quite different plenums offered presently on eBay are:
Jaguar 1940-50’s Plenum and Two Carburetors , eBay item number 282360248571
Jaguar 1950’s Mk 7 3.5L Carburetors and Intake OEM , eBay item number 191907306946

Rob, in spare parts catalogue which I have the parts numbers are as follows:

The 2.5 Litre MARK IV used C.1808 - which is the same as You wrote :slight_smile:

but then… 3.5 Litre MARK IV used C.1809

The question is are the parts C.1809 and C.2594 the same?

We are talking about LHD cars.

Thank You Roger,

the first eBay item is not the one I need. As in my first post - the bottom part of plenum should be flat not curved.

eBay item number 191907306946 seems to be the part but I can’t see inside.

Rob, have You got part number written anywhere on Your silencer?

If you search for “images” using “Jaguar Mark iv engine” you will see many types of silencers which have been used. A lot of Mark IV cars have plenums similar to, or perhaps from, Mark V cars. There are Mark IV cars with dual silencers hanging downwards from plenum, RHD cars. There are Mark IV cars with LHD and corner-cut plenum and also no corner-cut plenums. Lots of choices.

Guys ,

to make things more difficult here is the scan of illustration of Mark IV engine bay during Road test - 1948.

No Air Filter silencer. May it be that this shows SS and not Mark IV?

This picture looks to me to show a plenum with two silencers hanging below (with only the top of one silencer visible). Such an arrangement can be seen in some of the photographs of Mark IV car engines which can be found on the web as well. The car shown in your Autocar picture looks to be a RHD.

Yes, my understanding is that the air cleaners hung down like the Autocar picture until they began doing LHD cars. Then for LHD they needed one that goes above the engine.
Looking at 537001 and 637014 on saloondata, these plenums do not have the angle shape on the lower rear, and it appears the steering column is lower than for Mark V. I think that clears up that mystery, the angle was only needed on Mark V.

Mateusz, you did not say whether you are looking for a 2.5 or a 3.5 setup?

The ebay item 191907306946 is from a late Mark VII or VIII or IX. No good to us with pushrod engines.
The ebay item 302188529772 is from a Mark VII same as my last picture, no good to us.
The ebay item 282360248571 is from a Mark 1 or 2, no good to us with pushrods.

Mateusz, you asked if my Mark V air cleaner has a part number. Well, it has a part of one anyway.

The overall length is 18 inches or 45 cm. The port diameter is 2-3/4 inches or 70 mm.

My understanding of Mark V air cleaners was that the 3.5 has a small port for a rocker cover breather, but that the 2.5 did not.
Mark IV 3.5 did not have a rocker cover breather at all, just the one on the side tappet cover.
As always, please correct me if I’m wrong.

The LHD MK IV aircleaner is different in that it does not have a breather to the rocker cover.

I imagine they will be hard to source , But if careful , one could probably neatly fill that hole in a MK V ’ aircleaner. The alloy manifold will also be rare . If the Mk VII was otherwise the same except for the carb spacing One could possibly weld up the holes for the carb abd mill flat and redrill. I know I did that basically for an inlet manifold for a 2 1/2 litre SS engine/ blowwer and have done the same for a 3 1/2 litre .

I suspect a bit of tweaking will be necessary to get the aircleaner to sit in the correct spot.

This car is RHD and the air cleaner s hang down from the manifold. One for each carby , These smaller aircleaners were , with slight variations to mounting on a number of cars. You might have seen them on M G TC / TD .

The carb spacing center to center on the 3.5 pushrod engine is 7.5 inches or 190.5 mm.
The carb spacing center to center on the Mark VII XK engine is 8.125 inches or 206.375 mm.
I don’t know the spacing on the 2.5 engine.
If you can’t find the right Mark IV air intake pipe, the Mark V pipe is your next best choice. There ought to be some available in Australia.

The breather in the rocker cover is an early example of positive crankcase ventilation before it was discovered that the road tube was a primary source of smog. PCV became a requirement in California on 1961 model cars.

I noticed an interesting thing about the Mark VII air intake pipe plenum. Instead of four threaded studs, it has two threaded and two non-threaded. They apparently realized it is really hard to get to those two nuts in the middle as I found on my Mark V, so they decided two nuts was enough.


WE just welded alloy pieces in the holes and redrilled them

Of course a few other mods were done at the other end pic attached
The MK VII carbs have two holes as breathers for the carb.

The MK IV doesn’t

Here it is , inverted for the blower and a couple of blow off valve attached , but the prinicple is the same

Yesterday evening I went to my mummy true original car and have done these pictures:

So Rob - Your filter is the same like the one in my original car - so now I know which one I need :slight_smile:

When it comes to the plenum - I will start to search it - sooner or later there should be one somewhere.


since I have original plenum as a pattern I’m thinking about manufacturing one.

Are they made from 100% aluminium?

Well, they are cast aluminum, which typically has small percentages of alloying elements such as copper, magnesium, manganese, silicon, tin and zinc.
Sometimes castings have the material specification number on them, but my Mark V plenum does not have any numbers at all.
I noticed there are internal ribs and the material is thicker around the tapped holes and thinner elsewhere. That probably explains the need for a core plug; it must have been quite a complicated sand core which needed a support in the mold.

The MK IV and MK V filters aren’t the same

The MK V has the smaller breather hole into the rocker cover , the MK IV doesn’t

Thank You Ed I did not noticed that difference - it means that they are not exchangeable when one want to stick to originality. I could also cut this small pipe and close the hole with some metal part by welding, and then paint whole air filter.

When it comes to the plenum - I have a opportunity to make few cast aluminum plenums from my original part.
If I would do that - would anybody be interested in acquiring this from me as I presume the bigger quantity the smaller price per item?

Are the plenums for Mark IV and Mark V the same?

The MK V plenum is different in that I think it has a cut off on the rear quarter to clear the LHS steering column.

It is possible to cast them , Some SS plenums had been cast here a number of years ago , Early SS and not the same plenum , but the same basic idea.

Hi,. Realise this thread is old,.but did you ever find a plenum for your MKIV?, going through my late fathers things I have found one.