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MG MGB Technical - oil filter housing conversion.

Can any member supply me with information regarding the conversion from the original upright paper type element filter as fitted to the early MG's to the original top loading metal cartidge housing, fitted to the later models. Does the housing have an anti-drain system or is that fitted to the cartidge itself? Are there any problems with start up, the time lag it takes for the cartridge to fill from empty? or is there any way to pre fill. Peter
p j mayo

If you have an earlier engine, obtain the top-loading oil filter stand (BMC Part # 12H 3273) and its rubber O-ring (BMC Part # 8G 619) that fits to the engine block, the machine bolt and copper seal that attaches the adapter to the engine block, and the copper washer and adapter for the oil hose (flexible pipe) that goes in front. This last item may not be needed, as there are two types of oil hose (flexible pipe) adapter fittings: one that uses a large banjo bolt (BMC Part # 1K 2142) along with an inner copper washer (BMC Part # 1H 898) as well as an outer copper washer (BMC Part # 6K 501), and one that uses a screw-on adapter fitting (BMC Part # AHH 6701) with a gasket (BMC Part # 6K 431). You will need the oil hose (flexible pipe) adapter fitting only if yours does not use the banjo fitting.

Make sure that the oil filter stand still has the anti-drain tube fitted in the stanchion. Avoid using oil filters that are taller than necessary, otherwise when the engine is shut off any oil above the anti-drain tube will drain out of the oil filter into the engine, leaving an air pocket that must be filled before oil pressure can be achieved, an event that can take place only after the then-displaced air enters the system of oiling passages (not a good thing!). Also, beware of short oil filters that are about the same height as the length of the anti-drain tube. These can cause the anti-drain tube to come into contact with an internal support inside of the oil filter, causing it to bend. This is sure to damage the combination anti-drain-back and by-pass valve. A difference of 1/8 (3.175mm) in the height of the internal construction from what is correct could give normal performance at low engine speeds, yet produce total disaster at full throttle. Consequently, any oil filter should be examined to be certain that all of the internal components of the oil filter should be at a minimum a full diameter of the anti-drain tube away from the anti-drain tube when fully tightened. Do not attempt to avoid this by cutting down the anti-drain tube by (12.7mm). This will allow more oil to drain out of the oil filter, thus requiring it to be refilled before proper oil pressure can be achieved, just as if you had installed an oil filter that is taller than is necessary.

Unfortunately, the filter mounting threads on the stanchion of the oil filter stand occasionally become cross-threaded as a result of the clumsy installation of a new oil filter. So, here's an old Tool & Diemaker's tip: you can do a reasonable job of repairing the bunged-up threads with a purpose-made thread file. Be very conservative with that thread file. Once you remove the metal, you can't put it back on. After you finish with the file, run a -16 sizing die over the threads to form them up properly.

The choices of quality oil filters available are almost endless, the best of these including those from Mann (Part # W917), Purolator Pure One (Part # PL20081), AC Delco (Part # PF13C), Motorcraft (Part # FL300), Volvo 3517857, Wix 51362, and NAPA 1068, but the most effective is also the easiest to install: the K&N Performance Gold Oil Filter (K&N Part # HP2004). They all use the same mounting thread of "-16 threads per inch (SAE). Note that even with a good quality oil filter, you can have a bit of a hassle getting the oil filter to screw on. If you attempt to simply spin it on, you risk cross-threading with the result of damage to the threads on the stanchion of the mount. Instead, lubricate the sealing ring with clean oil and then try turning it in the opposite direction, with a little downwards pressure, and you will feel where the threads meet. At that point, turn it down onto the oil filter stand. It is all a bit of a learning experience, one that many of us have gone through. If the only oil filter that you can get for the B Series engine is the K&N oil filter, then you have definitely lucked out. Its resin-impregnated filtration element filters down to both 2 and 3 microns and its construction is as rugged as it can be. That makes it unique as all of the other filtration elements only filter in one size only. It even has a spring-loaded bypass valve in case of a clogged filtration element instead of a simple flap-type plastic bypass valve. Even then, it can handle up 550PSI before the reinforced filtration element collapses under the pressure. A high-pressure oil pump in a B Series engine can only attain a bit more than 100 PSI, so you are quite safe there. The 1" nut on top makes it a snap to get off when the swollen seal of other filters would cause it to refuse to budge. Needless to say, it is the oil filter that I always use, even if it does cost more (you get what you pay for).

To my knowledge, there is no way to prefill the filter cartridge prior to installation. However, you can prefill the system before firing the engine by disconnecting the ignition and cranking the engine until you get an oil pressure reading on the gauge on the dashboard. When the ignition system is turned on, voltage is applied to the positive (+) contact of the ignition coil, or the negative (-) contact on positive (+) ground (earth) cars. However, the current cannot flow unless the circuit is completed. The low side of the ignition coil is grounded, and thus completes the circuit, by the action of the distributor to which it is connected at the contact that is marked Input from Coil. If you want, a separate switch for the fuel pump can be installed in order to allow the engine to crank and thus build up oil pressure without drawing fuel into the engine in order to consequently protect the bearings prior to cold starting the engine. When shutting down the engine, the fuel pump can be switched off prior to switching off the ignition system, and the vacuum created by the fuel induction system is then permitted to draw the fuel out from the carburetor float bowls until the engine stalls. This permits the engine to be cranked in order to build oil pressure without flooding the engine.
Stephen Strange

Mr Mayo, this conversion is very easy to do and can be done in about the same amount of time as it has taken Mr Strange to type out his reply. I did this to mine sometime ago, I only use mine about once a week in the summer, and after standing all week it would take quite a while for the oil pressure to build up, now it is instant once it has been initially primed, the correct filter can be obtained from the MGOC stores, A.T
andy tilney

The metal oil filter has an anti drain-back valve (or should have, they vary in quality and effectiveness) and the housing should have an anti drain-back tube sticking up the middle of the filter. If you have the tube make sure your filter is long enough to give plenty of clearance to the top of the tube.
Paul Hunt 2010

Paul, the filter housing that your talking about, is that the OE spec that was fitted to the later MG's? and is that the type with the anti-drain tube?........
"should have an anti drain-back tube sticking up the middle of the filter. If you have the tube make sure your filter is long enough to give plenty of clearance to the top of the tube."

.....If so does the tube stick up thro the threaded portion where the filter screws on. The one I'm looking at has the bolt to engine on one side and a threaded spindle on the other, should you be able to see the tube? I'm looking to install a K&N HP2004 FILTER. Any one got a picture of the housing and tube please. Peter
p j mayo

Mr Mayo, if you go onto the MGOC website and look under spares, there is a full discription of every thing you need, first go to MGB engine, then oil/ filtering (mgb) and its there part number 12H3273, you can buy the housing for about 10-00 from most MG second hand parts dealers, A.T

andy tilney

Andy I do appreciate your comments but I rang the MGOC on Thursday and the part no 12H3273, is no available and the adaptor sold by Moss has had reports of filter bolt failure. I do have the option of a second handtop loading filter housing but cannot be sure that it is the one with the anti drain tube as I dont have a picture of it to show you. There is a picture of one on Watford Classic Cars,,in UNDER THE BONNET item FCK1 Suffice to say its the same configuration as the uright canister type that holds a paper element, the housing bolts to the engine block inclined at about 45 degrees and the filter housing has a raised threaded portion about 1.5 inches high that the filter screws down on. What I want to know is where is the anti drain tube? People say that you must make sure that the filter that you fit has enough height so as not to bend the top of the tube. the one that I am looking at only seems to have a threaded portion for the filter. Peter
p j mayo

Peter. The anti-drain tube is an upright, standing tube made out of steel, which comes out of the threaded portion of the 18V oil filter adapter. The Mann W917 oil filter, used on Volvos, fits this application quite well and I have been using it for about ten years since it was recommended here. This filter has an excellent anti-drain back valve in it which works with the tube to keep the filter full of oil when the engine is not running. Average time from starting to full oil pressure is under three seconds when the engine is in regular use. Takes about five seconds on cars that are only driven occasionally. There should be thousands of these adapters available on the used market in the UK.

Check to make sure the threaded section that the oil filter screws onto is in good condition and has not been damaged by cross threading or over tightening. Beyond that, "No worries, Mate" as they say in Oz.

Les Bengtson

Mr Mayo, I am sorry but my reply my not have been very clear, yes that part is no longer available,that is why i said you can get one for 10-00 secondhand, i do not have a photo to send you, that is why i said look in the MGOC parts list, in the picture you can clearly see the anti drain tube, which is part of 12H3273, if you still have no luck i have a few of these parts,one of which i may be willing to part with, A.T
andy tilney

Andy,many thanks for your info, I couldn'd say too much at the time as I was bidding on Ebay for one of these units. I won the bid and am awaiting delivery. I checked the one on the MGOC website and it does look as if the one I have purchased does not have the anti drain tube in it but I wont know till it arrives. If not maybe You will let me contact you again with a view to a possible purchase. Regards Peter
p j mayo


Your description of the unit you have purchased is very like that I fitted to my 69, replacing the original cartridge unit as you are seeking to do.

My unit is not the original MGB one which has the standpipe posters reference above, and, I believe, also has a pressure by-pass valve inbuilt. Rather mine is thought to have come from an Austin/Morris Major Elite, of the same early period.

This came with a 1/2" BSP filter thread. This is something you will need to take care with and check to avoid damaging threads forcing a wrong filter on. The single filter here for the 1/2"BSP thread is the Ryco Z23, an excellent filter but troublesome to obtain (special trips to a distribution centre or needing to be ordered in through motor chains)

Just this last week I changed that 1/2"BSP thread unit with a 3/4"UNF one a local club member machined for me. This change has opened up a wider range of filters I can use, each of which is also cheaper than the Ryco Z23.

A good local 3/4"UNF filter here is the Ryco Z38 - also fits some Ford Capri's of the period. That brand appears to be in NA (Purolator site) as Gudd, the name of the New Zealand manufacturer. Mann filters show both Ryco and Gudd as brands in their cross-referencing.

I have a Valvoline V067 (equivalent of the Ryco Z38)fitted at the moment and it appears to work very well, oil pressure needle at or past 40lb as the engine starts. Certainly appears to be as good as the Ryco brand I have used for 35 years.

The Valvoline and Ryco Z38 filters contain both the standpipe and pressure by-pass valve missing from my adaptor unit, as well as the anti-drain flap covering the oil feed holes in that ring around the face of the filter. A number of our local club members here are content to use filters without the standpipe, relying on the anti-drain valve to retain an acceptable volume of oil in the filter between runs.

Roger T

Here's one part of the problem solved:

N Dring

Many thanks Nick,see what you mean,re position of the anti drain tube.Wish I'd seen that ad before I bought the other one as mine does not show the anti drain tube. Im wondering if its a spare part that can be fitted later. Peter
p j mayo

I would think a standpipe could be pressed into the throat of the thread unit. Would need to be careful on the length relative to height of filter/s likely to be used, but that should be measurable from the sealing ring/sealing face points.
Roger T

The tube may well have been an afterthought, from what others have said theirs can be pulled out and pushed back. It is also said to be a steel tube in an alloy threaded boss.

I also use a Volvo/Mann filter because it had better anti-drainback performance over others I have tried, however I only noticed last year that it is significantly shorter than the recommended Unipart/Champion item, but haven't yet had the opportunity to measure the two. I'd also tried a K&N Gold, which gave equally good performance, but was double the price of the Champion/Unipart, 50% dearer than the Volvo, but was no better than the Volvo. It was also a pain to get hold of needing special order and a trek across Birmingham to collect, so I went back to the Volvo. Incidentally a Unipart GFE121F sold by some suppliers as being with an 'improved' valve is made by Fram and had a *worse* performance (on the gauge) than the Champion. I still use Champion on the V8 as they are hanging so anti-drainback is largely irrelevant, except for siphoning.

The Volvo has a spring extending downwards from the closed end of the filter, presumably the tube slots inside this, but will still allow oil to flow. The Champion just has a 'nub' at the end, both are presumably the bypass valves for if the filtration media becomes blocked, moved from being in the housing for replaceable element types.
Paul Hunt 2010

PS. *External* heights of the recommended Champion and Volvo are 4" and 3.25" respectively, internal clearance to the end of the bypass valve is 2.785" and 2.57" respectively, so not much internal difference given the significant external difference.
Paul Hunt 2010

Hi Andy/ Paul, this is the picture of the oil filter housing in question that has the tube fitted in the spin on section. Does that give you the anti drain properties or is there a valve within the housing below the tube? as the one I puchased looks to be the same minus the extension tube and its just hollow at the bottom. If I have got this completely wrong, and it wouldn't suprise me if I had is the anti drain valve in the filter and not the housing HELP. Peter

p j mayo

here is the images of the housing I have at the moment

p j mayo

second image, showing numbers on base. As you can see there is quite a difference between mine and the very oily one that has the inbuilt tube/drain valve whatever Peter.

p j mayo

The tube in the housing is one half of the anti-drain feature, there should also be a valve in each oil filter canister itself which provides the other half. One stops it draining out of the inlet, and the other out of the outlet. The only valve with the earlier suspended replaceable element i.e. the earlier housing was a *bypass* valve, for if the filtration material became blocked, and that was in the housing as the filter element was little more than filtration material. This bypass valve is part of the later canisters, as well as one of the anti-drain valves.

According to the Parts Catalogue the first canister housing was 12H3273, from March 70 to Sep 73, and inverted. It changed to suspended from Oct 73 to Jan 74, part number 12H4405, then back to inverted again From Feb 74, the previous part number. It's possible they changed to the inverted canister without the tube, noticed the drain-back problem, changed it to a suspended canister, forgetting why they had changed to inverted in the first place i.e. clearance issues with the new filter, and had to go back to inverted but this time with a tube pressed into the housing but didn't change the part number.

My 72-built, 73 model year roadster has the anti-drain tube, implying the first housing did have it. However that is on a Gold Seal engine i.e. fitted after the car was first used, but how long after I don't know. It is of the correct type for the year, but of course could have been fitted after the housing reverted to inverted again in Feb 74 and had been modified.

With the tubed housing make a note of how long it takes for the pressure to start rising after an oil and filter change, and compare that with normal starts. If you find that after a couple of days it takes as long, or even worse if that happens over-night, then the valve in the filter itself is either very weak or not working at all. If you find it starts creeping up towards that time overnight towards by the time the next oil and filter change is due then the filter isn't bad, but the valve is getting tired. Really the valve should continue to function fully for at least 3000 miles, that is what I find with the Volvo.
Paul Hunt 2010

Hi Andy, further to my problem re the oil filter housing I unfortunately missed out on the one on ebay that Nick kindly told me about,so I was wondering if your offer of a tube to fit the housing I have is still on. Regards Peter
p j mayo

Changed my filter this week, and measured the tube length at 2", so fine with the shorter Volvo filter. However for the second time out of three the new filter has spurted a bit of oil out past the seal on first start, which I have never had with any other make. I think this must be the seal distorting on being tightened, I thought I could feel it when tightening it, so backed right off and tightened it again but not so much, but still got this momentary burst of oil. There is no info on the can about how far to tighten it after the seal contacts like other filters have, I think anything beyond a quarter turn is risky.
Paul Hunt 2010

I've always "over tightened" spin on oil filters and never had one leak on me. Paul, I suspect the filter that you installed has a faulty seal. RAY
rjm RAY

OK, two out of three Volvo/Mann units then!
Paul Hunt 2010

Paul, you might want to inspect those filters a little closer. It sounds like the rubber seals may not have been properly fitted at the factory. RAY
rjm RAY

It's also two filters out of three over three years. If the rubber seals haven't been fitted properly, then I think Volvo service staff would have noticed by now! It has to be overtightening by me, the Volvo units obviously can't be tightened as much as I'm used to. Yes, the Volvo filters are different to Champion, for example, but they must also be intended to be that way or they would have been corrected by now. Unless I was just unlucky and got two bad ones? I don't think so.
Paul Hunt 2010

Paul, calm down. In the 40 years of changing oil filters I have never come across a seal leaking and then sealing itself on an oil filter. Do you really expect Volvo to call you up and tell you that they had a bad batch of oil filters? RAY
rjm RAY

My 1965 was re-engined by the PO some time ago with an 18V engine big valve. I have the hanging cartridge unit Paul H describes. It's a little hard to change the filter but that bad. I suppose they are out there somewhere used. The filter is pretty common so that's not an issue.

I assume a pre-engaged starter and alternator will work with this set up as it came from a 73-74 year model as Paul said. Originally it was without a cooler using a steel oil pipe.

Bob McCoy
Robert McCoy

Ray - of course not. Do you think Mann are going to make bad batches for Volvo for three years?
Paul Hunt 2010

Peter ,I am sorry i have not replyed to you, i have been stuck in Spain for the last 10 days,as i could not get a flight, my 7 day climbing trip turned into 17, and i have just got back, let me know what you need and i will send it to you, PS. let me have your email address, A.T
andy tilney

hi andy you were stuck out there and I am now out there on holiday,but not stuck at least not yet as we drove out here. we will be returning on may 19th. Ive managed to get a wi-fi connection out here so just got you BBS thread. the housing that Ive got has not got the tube for the anti drain,thats all thats missing I am presuming that one can just be pushed in as an interference fit? My email is, many thanks Andy. Peter
p j mayo

This thread was discussed between 05/04/2010 and 05/05/2010

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