Mark IX Oil Filter

I am rebuilding a Mark IX 3.8 engine using some parts from a Mark VII 3.4 engine. I removed the oil filter housing from the 3.4 and it bolted directly to the 3.8. Do any of you experts know if this filter assembly will work on the 3.8.? Personally, I don’t see why it won’t but wanted to check with you guys.
Pat H.

Don’t know anything about the car but it looks like it hangs to low could get hit ?

Not entirely sure, can’t see why it wouldn’t but just make sure you are using the correct oil filter head gasket and that none or the oil passages are blocked.

The oil sump is lower

It should work just fine. Make sure it has all the proper pieces and rubber seals.

There are two types of filter mounts. The early mounts bypassed excess pressure/flow directly back into the area above the sump via a hole in the block. Engines that used that mount have 3 holes in the block skirt behind the filter mount. The second type used an external hose that ran to the side of the sump below the normal oil level. Blocks that used that type had only 2 holes in the skirt.

Your photo shows a sump with a provision for the external bypass, but the earlier Mk7 mount, which vented through the block skirt. You need to verify that you have the third hole in the block skirt that accommodates that style mount.

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I do not think this will ever work.
There is no oil pressure relief overflow out of the filter to the sump.
I have a XK140 that does have that same oil filter housing.
But on my block there are 3 holes, on that latest picture there are only 2 holes.
There is one for the pickup of oil, one for the oil gallery and a 3e one for the pressure relief.

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Yes sir, that is correct… That’s what I was saying. The last two photos are of an engine I built, not Pat, who posed the original question. They show a two hole block that was used with the external bypass filter mount from an XJ6.

Mine is different from the one you are showing. The filter housing has three passageways. My question remains “Will this work?”
Pat H


Only if the block has 3 matching holes.

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If the photo you just posted is the block you intend to use, the answer is yes, it will work. You have to have all three holes to use the early mounts with the internal bypass.

Thanks. Now to find the correct filter element. Failing that I’ll probably use a spin on conversion.

The mk9 was fitted with 2 types of oil filter. Early models were fitted with the same type as the 7s and 8s and later models with the same as on the MK2 etc. My mk9 is a 1959 and has exactly the same set up as your picture shows so I think you’re good to go, especially if your block is an early one.
If you find 2 sealing rings in the oil filter box you need to use the thinner of the two. It is a square section ring, not an O ring.
There are posts on the sealing ring business. Many leaks are because the so called specialists haven’t supplied the correct one.

Thank you. Have you found a reliable supplier for the filter?
Pat H

I live in UK and NOS still turns up at autojumbles fortunately.
I think Barratt’s were selling them, but the sealing ring might have to be purchased from them separately.
I have posted the dimensions of the correct sealing ring on this site a couple of years ago, along with the dimensions of the one which is sometimes used but doesn’t fit properly! One sealing ring lasts 2 or 3 oil changes. It’s often easier to fit the filter at the workbench with the complete assembly removed from the car.

All XK blocks have the same 2 main oil feeds and outlets , any oil filter will bolt on , some have 5 bolts some have 4 , just look at all the diffrent models of oil filter housings they made , long as you use the right gasket , cant see there being a problem !

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Not so simple, you cant match a 2 hole filter head to a 3 hole block. The bypass will not be able to bypass, resulting in excess oil pressure when cold, it could damage something, probably the oil pump.

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A very relevant post by Ian

Do you, (or anyone else), have a MK9 filter head to compare against the MK7 one ?

I went thru this when I had to install a 420G filter head on a S2 XJ motor

Yep. Won’t hurt the pump, though. You would blow out the seal on the filter housing first. Gear and rotor pumps are very tough. Virtually immune to back pressure, they pump the same volume per revolution whether they are pumping into an open bucket or a 1,000 psi process. If they turn, they pump until you run out of horsepower to turn them.

Don’t underestimate the hydraulic power, it can blow seals, split casings, strip teeth - - -