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The XPAG Core Plug: a Temporary Solution

4 Mar

The subject of core plugs is seldom on the T-Type owner’s mind until things go wrong; then the consequences can be nasty if you lose one or suffer a slow leak of anti-freeze from a corroded core plug disc – especially if it happens to be in the worst place possible for replacement in situ and you do not relish the thought of an engine out job.

First we refer to the large 48mm diameter core plug at the rear of the engine block on practically all T-Types. Solutions have been mooted over the years in the past in our journals etc and some with moderate success, but is there a solution which, given a little D.I.Y. time and tools, could result in a temporary remedy and get you going on your journey say within the hour when you are in the middle of nowhere!! and, of course, if you carry extra water?

I remember reading an article in the Octagon Bulletin some years ago on this subject; the idea was to use two core plugs bolted together and as you tightened the centre bolt it expanded the core plug to make a temporary seal. This got me thinking about a similar method and one which could be accessible to fix in situ.

The problem, as many owners will be aware, is that there is very little room in which to work on all the core plugs, least the rear large one. As luck would have it, Peter Harrington, a very good friend of mine and M.G. owner of three T-Types had an engine waiting for overhaul in his workshop. I was therefore able to bench test a device in principle which would solve the problem and be an easy to fix as a kit.

This was done by first making a special core plug 48 mm diameter (1 7/8”) which was domed but with a flat outer rim 5/32” width with a centre hole 3/8” diameter (photos 1 and 2).


Photos 1 & 2: on the left, the domed side of the special (brass) core plug; on the right, the dished side.

Next a steel bar was designed which has a central set screw welded and reduced head thickness which can be domed, the bar radius at the ends so that the bar would then fit inside the water jacket of the block.


Photo 3 – steel bar with welded central set screw

Finally a special aluminium disc was made with a threaded centre hole 3/8” diameter Whitworth or B.S.F. and also domed to suit the profile of the special core plug; its width was 1 1/16ths inch and on its outer diameter was drilled four tommy bar holes 3/16ths inch diameter (photos 4 & 5).


Photos 4 & 5 – showing both sides of the special aluminium disc


Photo 6 – the complete assembly. Not previously mentioned in the text is a cork gasket (located between the special brass core plug and the steel bar – later referred to in the text as the metal anchor plate) and a rubber grommet which is located between the cork gasket and the steel bar.

The outer diameter of the aluminium is only about five to ten thousands of an inch smaller than the core plug diameter, so to fit the kit in place, first we have a good quality sealant which is used on the gasket to core plug and engine block aperture, the steel bar, a rubber grommet 3/8ths bore to fit over the centre set screw, cork or paper gasket with a centre hole 3/8ths and outside diameter the same size as the core plug, then fit the special core plug in its rightful place in the engine block. In most cases the metal anchor plate will only fit correctly in one position for example the rear 48 mm core plug the anchor plate will only fit at five to five (as on a clock face), so you line up the slot cut in the threaded pin to this position and spin on the threaded aluminium disc and moderately tighten to give a leak proof joint.

A small lock nut can be used as security if required but generally if you apply plumber’s PTFE Tape to the threads things should be O.K. Also I did apply sealant to each side of the rubber grommet which would help to seal the threaded centre screw and grommet to gasket centre. Now in an extreme case you may be able to use the standard 48mm core plug with a good gasket, preferably cork or steam gasket also a different profile threaded Aluminium disc is required which is more simpler to make for which a drawing has been produced, and if needed the same set up can be used on the smaller diameter core plugs but in both cases a centre hole 3/8ths inch diameter has to drilled accurately finally using a good quality sealant.

Ed’s note: At this point, I think a few photos will help to explain the set up and how it is fixed.


Photo 7 – the complete assembly as descibed in the text. Note the rubber grommet on the steel bar and the special spanner which locates in the 3/16” tommy bar holes on the face of the aluminium disc (shown in photo 5)


Photo 8 – steel bar with welded central set screw ready to be inserted in back of block


Photo 9 – steel bar with welded central set screw now inserted in back of block


Photo 10 – cork gasket fitted


Photo 11 – special brass core plug fitted


Photo 12 – aluminium disc being tightened using a tommy bar engaged in 3/16” holes

Coming on to the M.G.TF which is the most awkward car to work on in this respect some American owners have cut the bonnet side to the same profile as the outer wing and made the bonnet sides removable with the aid of M.G.A. large washers, in all about six bolts in order to make work on them a little easier. For the smaller core plugs of 1.3/8ths inch diameter a similar system can be employed, but replacing the core plug, which is the rear one in the water channel (which also has a small drain hole which must be clear) which you should check when replacing the core plug, is difficult because it is in direct line with the steering column.

So to aid the installation of this core plug the Aluminium threaded centre disc has four peg holes 3/16ths diameter drilled on its surface so that a special “C” Spanner or circlip spanner can be used (see photo 7) and it’s a system which can be used for the core plugs on the side of the engine block after you have removed the old core plug and cleaned its aperture before fitting this temporary kit. When fitting standard core plugs it is always best to make sure that they are a tight fit in the engine block aperture before you use force to seal them, and to do this place the core plug on a flat steel surface gently tap the radius surface around halfway towards the centre of the plug until you get a good fit, finally fitting using force to seal, avoid flattening the centre of the plug to much because in extreme cases you can actually reduce the diameter of the core plug.

A set of drawings is available for members wishing to make this core plug kit if so desired. Finally I would like thank Peter Harrington for his patience, practical knowledge and advice in fitting this temporary core plug to the XPAG and XPAW engine blocks.

I hope this article is of interest to our members which may create sufficient need that manufacture of a limited number of these kits should be possible.

A. Atkins

Ed’s further note: Whilst we are on the subject of core plugs (sometimes referred to as “freeze plugs”) the correct sizes for the XPAG are 6 x 35mm (1 3/8” will fit), 2 x 48mm (1 7/8” is too small), 1 x 45mm (for the cam). I am indebted to Bob Grunau for this information.

Regarding corrosion, it helps to paint the inside of steel core plugs with red lead (if the ‘Elf’ and Safety brigade haven’t banned this) or a similar rust inhibitor.

A supplier of brass core plugs is TTT 2 member Tom Lange. Tom’s contact details are as follows – Website: www.mgtrepair.net E-mail: tlange’at’acadia.net

When fitting core plugs to the MPJG block, Brian Rainbow cautions to exercise extreme care as these blocks are notoriously weak and you may well end up cracking the block if you are not careful.

Supercharging the XPAG

2 Jan

I read with great interest the recent article by Colin Hooper in TTT2 # 7 on his experience of installing a supercharger on his 52 MG TD. What captivated me about the article was not the supercharger system, but rather his opinion of it, as I am the guy who designed and built it.

Supercharging a MG T-Series today is nothing new; in fact when our cars were in current production there were over half a dozen different manufacturers that were making kits. The enthusiast driven aftermarket quickly saw the limits of the mighty XPAG and jumped on the opportunity to add some sorely missing “grunt” to Abingdon’s meagre effort. English companies such as Shorrock, Marshal-Nordec, Arnott and Wade made superchargers, as well as the Italians with SCoT and Itel-Meccancia.

Even we colonials got into the act with our American home-grown effort from Judson. Most MG T owners nowadays tremble at the thought of supercharging their cars as they all have heard the dark tales of destroyed engines, broken crankshafts and mushroom clouds of lost money. In these stories the teller usually has forgotten to mention that when the alleged engine failure occurred, he was p*s*ed out of his mind, running 7,000+ RPM and fitted it to a worn-out old lump with millions of miles flogged on it. The truth is a properly set up supercharged engine is every bit as reliable as a normally aspirated one, maybe even more so.

How? A supercharged engine is able to make more power at a lower RPM than an atmospheric induced one due to better intake charge distribution. Also the power impulses on the crank tend to be more equal in strength as the intake charge is under pressure.

How does it all work? In a perfect world (with our XPAGs being 100% efficient) when the intake valve of a XPAG engine opens, air and fuel fills the 312.5cc volume of each cylinder with the pressure of the atmosphere at around 14.7 psi. The net result of all this is around 50 horsepower produced at the crankshaft. Now if the pressure filling the cylinder were raised by 50%, you would now stuff 468cc’s. into the same volumes yielding a corresponding increase in power. So a supercharger adding an additional 7.5 psi pressure or “Boost” to the intake system, should now give you 75 horsepower.

The reality with our XPAGs is we really only see about a 40-45% increase due to the inherent inefficiencies of the engine. Still a 45% increase is wonderful improvement; remember that when you are pulling on to the motorway next time with your stock spec motor.

XPAG Dyno Results Graph
Note: All dyno measurements taken at the rear wheels.

Marshall-Nordec Supercharger
One of the more popular Marshall-Nordec superchargers as fitted to a TD. Photo: author unknown, but thank you!

Arnott Supercharger
An Arnott installed on a TC. Photo: author unknown, but thank you!

The superchargers originally offered for the XPAG engines fell into two basic categories: “Roots” pump type superchargers such as Marshall- Nordec, Wade and SCoT and concentric compressors, such as the Shorrock, Arnott and Judson. These two different type superchargers achieve the same result of pressurizing the intake system of the engine, but go about in two different manners. The Roots design is an air pump; it makes no pressure internally in the supercharger, but pumps the manifold with fuel and air faster than the engine can ordinarily consume it, creating pressure in the intake tract. The concentric superchargers trap a volume of air and then internally compress it before releasing it into the inlet tract. The German word for supercharger is “Kompressor” and Mercedes proudly emblazes the sides of their product with it, though in reality, they actually use a “Roots pump” type supercharger!

For years I have fooled with superchargers on MG T-Types; this initially involved rebuilding old units and in many cases, making new parts for them as well. The problem is that the original units that crop up for sale on Ebay and at the autojumble, are 50+ years old, expensive, often need rebuilding and lord help you if you need replacement parts!

After years of supercharging MGs, I became involved in supercharging current production vehicles as a vocation. I was supercharging new cars during the day and old ones (MGs) at night. It was bound to happen, and it eventually did; the two crossed and a new XPAG supercharger system was born. I was working for Moss Motors at the time developing Mazda and Honda superchargers for their Jackson Racing division. For the T-Series, I chose to use an older design “Magnacharger” M60 as it had the right flow characteristics and a vintage look and these units sold well until the manufacturer decided to discontinue the unit. I think Moss sold around 200 of these units over a 4 year period. During this same time I left Moss for greener pastures in the supercharger field, but not before I designed their MGB supercharger system as well.

Moss Supercharger
One of my ”Moss” systems installed on a TF 1500. Photo by author.

Even after I left Moss, my MG brethren continued to hound me for a new XPAG blower as Moss’s supply had now dried up. By this time I was working for a major OEM supercharger supplier and was supercharging tens of thousands of TRD Toyotas and new English vehicles as well; the current Lotus Elise SC and Exige. I built a handful of new systems for the T series using an Eaton based MP45 supercharger built by my current employer with parts based on the old Moss system. By happy coincidence, those parts ran out at the same time as the supply of the appropriate blower to fit them dried up. This forced me to start from the beginning for the third time with a clean sheet of paper. This new system was inspired by the vintage predecessors but uses modern technology to achieve a better result. I also added all the improvements I had learned from the earlier iterations. This Supercharger is designed to fit the XPAG and XPEG engines fitted to MG TB-TC-TD- TF sports cars from 1939-1955, providing a boost pressure of 6-10 psi depending on engine configuration. Higher boost levels are possible and this supercharger under racing conditions is capable of supporting an engine to over 150 bhp with the correct modifications as necessary.

MG TA Hill Climb
Jakob Vigselo at the Skilborg, Sweden hill climb in his 150+HP Mirage Garage supercharged XPAG engined TA. Note all four wheels are off the ground! Photo by Nils Millar

With my new system, I felt I needed it was time to give it a proper name other than “just another one of Terry’s blowers”. Years ago one of my MG mates, Craig Cody dubbed my home garage “Mirage Garage” as I was always working on MG projects there. Well the name stuck as I now had a product for a business that does not exist. (hence the Mirage aspect) The new Mirage Garage supercharger is the result of over thirty years of supercharger experience and development. It utilizes the latest Eaton 5th generation MP45 supercharger technology as used on the Lotus sports cars and In fact the internals of my blower are directly interchangeable with these cars. The standard kit will deliver 5-7 pounds of boost which is good for about a 45% increase in rear wheel horse power. The big boost kit that makes 8-10 psi is available too.

The supercharger unit is completely self contained with no need for external oil supply or drain lines, with the first recommended service at 100,000 miles, or in XPAG years, about the time your grandchildren will seek their pensions. The kit comes with everything necessary for installation except the carb. It uses a SU H4 (1-1/2”) carb with some minor mods explained in the installation instructions. The supercharger installation requires no cutting or drilling and is completely reversible.

In Colin’s article, he added an additional fuel pump, but unless you are going hard-core racing, your single, standard S.U. fuel pump will work just fine. Installation time is four to eight hours depending on the vehicle and your beer consumption. To date I have over 50 successful installations.

Mirage Garage Supercharger
The latest offering from Mirage Garage fitted on a TC. Photo by author.

Mirage Garage Supercharger
The “Mirage Garage” Supercharger kit. Photo by author.

Driving a stock MGT in modern traffic can be a harrowing experience. You have a limited amount of power and must struggle just to keep up and not get run over. So to answer the big question: “What is it like to drive a supercharged MGT?” Here is a real world example: In the course of my testing there is a hill in my home town that is quite long and steep with an eight percent grade. When climbing it in my absolutely stock ’53 TD, I found myself crawling up in 2nd gear while winding the engine at very high RPM just to try to stay up with traffic. Supercharging the same car, I can now blast up the hill quickly in 3rd with modest RPM. It is a good feeling to know you are able to run with modern traffic, and that you have reserve power to get you out of a tight spot. Distribution of my new Mirage Garage Supercharger kit is handled in the UK by Steve Baker at Steve Baker MGs steve ‘at’ stevebakermg.co.uk and in the USA by Tom Lange at MGT Repair and by myself tpeddicord ‘at’ rocketmail.com for the rest of the world and the USA.

Once you try a supercharged XPAG, you will never want to go back to a normally aspirated engine again. It is true what they say about power, it really does corrupt you!

Terry Peddicord

Ed’s Note: Thank you Terry for an interesting article with some great photos.

Crankshaft Rear Oil Seal

1 Mar

Roger Wilson has written a comprehensive article on the infamous engine leak at the rear of the block in the May 2010 edition of “Totally T-Type”. This excellent article prompted me to look at a spare ‘Gold Seal’ reconditioned engine block, which has revealed an additional problem and also paved the way for trying out an old remedy. In this article, the term “oil scroll housing” is used to describe that part of the “main bearing cap” that surrounds the oil scroll on the crankshaft.

The first step was to make up the setting gauge (Photo 0) detailed by Roger in the September 2010 edition of TTT.


Photo 0 – making up the setting gauge

This revealed that Roger may have been optimistic when he suggested that “The oil scroll housing on the rear main bearing cap will have a uniform clearance all round as it was bored in line with all the main bearing housings”. In this particular block I measured 0.006” clearance on one side, gradually diminishing to less than 0.001” on the other (Photo 1).


Photo 1 – Feeler gauge inserted between housing and setting gauge

My first thought was that the setting gauge was not seating properly, so to eliminate the gauge, the rear main bearing cap was mounted on a mill table and a Dial Test Indicator mounted in the chuck was then used to check the concentricity between the oil scroll housing and the shell bearing housing (Photo 2) This confirmed the 0.006” misalignment.


Photo 2 – checking the housing with a DTI

A magnified inspection of the oil scroll housing’s surface suggested that some rubbing against the crankshaft’s oil scroll had taken place. This leads me to believe that wear in the main bearings could have been considerable, thus allowing the crank’s oil scroll to contact the housing.

But why double the wear on one side compared with the wear on the bottom of the shell bearing?

This might be explained by the tendency of a rotating shaft to climb up the bearing’s side. The location of the excess wear on the near side of the engine seems to support such an idea.

Rather than have the main bearing cap line bored, I chose to machine the oil scroll housing to be concentric with the bearing housing (Photo 3) and set up a uniform gap of between 0.01” and 0.015”.


Photo 3 – Machining the housing

The object of this slightly alarming approach was to make use of a suggestion by the late Ray Sales, some 15 years ago.

He ensured concentricity between the crank’s oil scroll and the housing by wrapping a single layer of sellotape around the crank’s oil scroll and spreading a thin layer of JB Weld on the oil scroll housing. The crank, bearings and bearing housings are then assembled, torqued down and the JB Weld allowed to harden.

On dismantling, the sellotape is removed along with any excess JB Weld. Such an approach should set up a truly concentric gap of about 0.002” (0.05mm). The extra clearance machined on the oil scroll’s housing allows a thicker, more robust layer of JB Weld and to improve adhesion a groove was also machined into the scroll’s housing (Photo 4) with a slitting saw.


Photo 4 – machining the groove

The slinger cap or oil thrower is the die cast cover plate that sits directly above the crankshaft’s oil scroll and is meant to be located by two 4 mm dowel pins and secured by three M6 screws to the engine block. The dowel pins had been removed, perhaps confirming Roger’s comment about the Morris Engine Division (responsible for the Gold Seal reconditioned engines), having to remove the pins to help correct any misalignment.

Using the gauge, a gap of 0.004” at the top of the slinger cap and a tight fit at the sides was revealed, suggesting a new cap had been installed. A light skim of the cap’s flat edge on some 320 wet and dry (Photo 5) and some judicious scraping (Photo 6) set up a uniform 0.002” clearance with the gauge.


Photo 5 – skimming the cap’s flat edge

As Roger has advised, some semi-hardening sealant either side of the gasket would help fix the cap’s location in the absence of the pins once the cap has been secured by its three screws. The use of some 0.002” shim steel wrapped around the gauge would help true the fixing of the slinger cap to the block.


Photo 6 – scraping the cap’s surface

All the above procedures should secure a uniform 0.002” clearance around the crank’s oil scroll, and whilst some slight leakage may still occur, a well set up oil scroll system should be inherently effective.

My conclusions support Roger’s suggestion that the oil slinger’s dowel pins were not always able to set up the correct clearance and that some individual adjustment is needed with the aid of a setting gauge.

Although the scroll housing should be concentric with the bearing housing, excessive bearing wear can result in increased leakage as the crank’s scroll abrades away the scroll’s housing. This can be rectified by expensive line boring or by reducing the clearance with a film of JB Weld. For good adhesion of this film to the housing, some care in preparation is needed, such as the use of a ‘Dremmel’ to grind away and rough up the surface.

If main bearing wear can result in abrasion between the crank’s oil scroll and the housing, then the crank’s oil scroll diameter needs to be checked and the setting gauge dimension modified to be compatible.

When assembling the shell bearings, the ends should slightly protrude by a few thou. above the housing. This allows a slight degree of “bearing crush” to take place when the housing is torqued down.

I hope this article will give encouragement and the reassurance that paying attention to detail, although time consuming, is worthwhile.

Eric Worpe e.worpe(at)btinternet.com

Ed’s note: As always, Eric is willing to pass on the fruits of his labours and in doing so enables others to benefit from his experience.

Engine Rebuild on TD13030

4 Jan


MNE 4 at Brooklands

MNE 4 is quite a well known MG TD having completed the 1952 RAC Rally in atrocious weather in late March/early April 1952 driven by Reg Harris, better known for his exploits on 2 wheels rather than 4. After 3 further owners, MNE 4 was purchased by Harry Crutchley in 1969, the year ”H” formed the MG Octagon Car Club.

I purchased MNE 4, in September 2009 from a dealer. He assured me that the engine had just undergone an extensive refurbishment including new liners and unleaded head conversion. Just over 1000 miles later, in April last year, the engine failed, losing power and making a very “expensive” sounding internal mechanical noise.

After extensive research I approached Iain Rooney (now one of TT2’s listed suppliers) to repair or rebuild MNE 4’s engine to period Stage 2 tune as that was the car’s state of tune when it competed in the RAC Rally. I trailered MNE 4 to Iain’s premises, near Selby in Yorkshire in May (see photo below taken on departure from home).

Iain dismantled the engine that day so we could understand the nature of the failure and decide a way forward. As the engine was dismantled, the full extent of its problems became apparent. The list of issues is too long to record here but to give you a flavour, we noted that it had the wrong cylinder head gasket, no liners or unleaded head, impact marks on all pistons from contact with the cylinder head, failed small end bearing on number 3 cylinder etc etc etc!


Engine strip down (above) and rebuild (below)

Iain and I agreed that the engine would have to be completely rebuilt using the block and cylinder head as the basis of the rebuild. All the internal moving parts of the engine would have to be replaced apart from the flywheel. Over the following few months Iain and I exchanged many e mails and telephone calls, verifying correct period parts were to be used. I sourced a period NOS dynamo and starter motor from Charles Russell of The Electrical Parts Company Ltd. I also found Andrew Turner to rebuild the carburettors to MG TD Mark II specification 578 SU H4 standard.

The rebuild proceeded through the summer months with Iain cleaning, checking, machining and fabricating all the parts required and using his extensive network of contacts, built up through many years in the business. The flywheel was lightened, the cylinder head gas flowed and a camshaft of Iain’s specification fitted. At a late stage it became apparent that the sump would need to be replaced. As had proved typical throughout the rebuild, Iain could find many examples of the larger capacity finned sump but could not, initially, find the smooth sump that would have been fitted to MNE 4’s TD2 (8 inch clutch) specification engine in January 1952. Fortunately, Ian found a “mint” example of the 9 pint sump and the build continued.

By November, having had numerous frustrations with period parts, the unbelievably poor workmanship previously inflicted on the engine and my insistence that originality should be the guiding principle, the rebuild was complete. Originality was sacrificed in one specific area. The original oil bath air cleaner and air inlet manifold were not refitted. I have seen virtually no period photographs of TD Mark IIs with those components fitted. Iain convinced me that the poor breathing caused by the air cleaner/inlet manifold combination would undo most of his efforts to produce the “fast” road car torque and power profiles of the rebuilt engine.


MNE 4’s rebuilt engine ready for installation (above) and installed (below) showing rebuilt carburettors

I am still running in the “new” engine but what a transformation! It is flexible and is raring to go with a delightful throaty roar from the exhaust. I would like to thank Charles Russell and Andrew Turner for their part in the process but particularly to Iain for his patience, professionalism and brilliant workmanship.

Paul Critchley

Editor’s Note: You can learn much about MNE 4’s history and National and Internationally renowned racing cyclist, Reg Harris, by going to the following website: http://www.oldclassiccar.co.uk/mg-td.htm

By the way, you’ll notice from the photo of the rebuilt engine that it has the TB/TC/early TD oil filter arrangement. This is quite correct as the engine fitted at the Factory to MNE 4 was XPAG/TD2/13087. This engine number falls between XPAG/TD2/9408 (the first TD engine with the 8 inch clutch) and XPAG/TD2/14224 (the first TD engine with the later oil filter arrangement).

I am indebted to Paul for his article (and useful endorsement of Iain Rooney’s services) and also for the photographs of the rear bumper TD MK II plinth arrangement and badge as featured in the TD Mk II badge article in this issue.