Notes On Rebuilding A TA Engine

Most of us probably remove the gearbox along with the engine but one of our good friends who's done this many times finds it easier to separate the two and remove only the engine.

Here's what he has to say:
"I normally take the engine out on it's own, so no need to disturb the interior and the gearbox. The only thing one has to remember is to put a container (catch pan) under the flywheel housing when you split this from the bell housing!! Also before removing the bolts from flywheel/bell housing remove the clutch operating arm from the shaft on the bell housing, by drifting out the dowel pin and prising the arm off the shaft (don't loose the woodruff key). If you don't do this first, you will not be able to separate the engine from the gearbox! Support the underside of the gearbox, and remove the two front rubber engine mounts from the chassis to give clearance to get the engine out."

Items such as the bonnet and radiator along with any other easily removed ancillaries would, of course, already have been removed. And you must remember to rotate the clutch shaft upwards (counter clockwise) when bringing engine and transmission back together. This will allow the fork to pass over the thrust bearing and settle in behind it else they will never mate up!

Another good friend uses this method:

1. Disconnect battery then remove seats, carpets, floorboards, prop shaft tunnel. Undo end clips of bonnet and lift off (place on carpet somewhere).
2. Remove gearbox remote (take care of 3 springs & balls at rear), disconnect front of prop shaft and speedometer drive from gearbox. Loosen gearbox support bolting.
3. Disconnect exhaust pipe (including support to underside of bell-housing) and starter cable.
4. Remove dynamo, oil filter & pipe (precaution), oil gauge pipe, distributor to coil wire, oil gallery pipe to cylinder head.
5. Remove carbs, inlet & exhaust manifolds, drain radiator & block then remove rubber cooling hoses, petrol pump (for clearance), cylinder head and rear two cylinder head studs (again, for clearance).
6. Undo locking nuts under radiator, remove large bolts holding headlamp supports to radiator cross member. Protect headlights then lift out radiator assembly.
7. Undo front engine mounting bolts, put engines slings under front of oil sump and rear of same.
8. (Two people are best from here on) Using two chain hoist on beam (sufficient to carry up to 5 cwt), take engine weight then remove front engine mounting bolts and gearbox mounts.
9. Release handbrake, slowly roll car back while lowering rear sling, then start lifting the front sling to clear the chassis. Eventually, nearing 45 degrees, it will be possible for the gearbox to clear the underside of the foot ramp and roll the car further while easing out the engine/gearbox.
10. Once clear of the rolling chassis lower the engine assembly onto a trolley, preferably fitted with a box support to the sides of the sump (not the base as this is weak).

It really isn't all that difficult or time consuming to remove the seats and floor boards. And it gives easy access to the drive shaft and transmission mounts as well as allowing a good visual check on the condition of everything else under there. But it is also nice to know that IF you want to remove only the engine it is possible. Don't forget the catch pan!

The MPJG engine was based on 1920's technology having evolved from older Morris designs and the blocks are said to have been cast from poor quality iron. The youngest of these is now over 75 years old, most are likely to have seen many years of abuse and replacement parts are increasingly difficult to source. Little wonder that several TAs were given XPAG engine implants. But for all its faults there's nothing more appropriate, and pleasing, than finding a well-maintained, original MPJG engine in a TA.

Repaired Block

It should also be remembered that anti-freeze, prior to WWII, was not generally available. And on nights when the temperature was expected to drop below freezing the water had to be drained from engine and radiators else they could be destroyed by the expanding ice. The MPJG block above may suffered that fate. Luckily this engine survived to continue running with the help of a brass plate 'sewn' to the side of the block.
(Note: Sad to report but after a year or more of service oil was found to be seeping into the water jacket and this engine block has now been retired.)

Where A Stud Pulled Out Of The Block

Because of the porous casting material used in some of the blocks extra care must be taken when torquing down the cylinder head. It is not unusual to hear of someone pulling a stud right out of the block and sometimes breaking out a section of the water jacket as well. There's just not a lot of deck into which the studs are threaded and with years of cleaning up and 'decking' that surface gets thinner and thinner. When replacing the studs be sure the threads have been cleaned using a tap and then coat the threads well with a good gasket sealant. The area of the casting around the core plugs is vulnerable as well. And it is now suggested not to hammer core plugs flat, as is the usual practice on 'modern' engines, but to epoxy them into place then seal them on the outside with gasket sealer. Another precaution is to apply a thin layer of solder around the circumference of the core plug before fitting, giving it a 'soft' contact against the block and possibly reducing electrolysis. And for longevity some rebuilders paint the inside of the core plug with Glyptal paint before installing them.

Some have solved the porosity problems of these castings by having the block and the head ceramicly sealed or impregnated using resins. (I did nothing inside the water jacket of the head or block but did paint the inside of the block and sump with Glyptal.) Locating a good MPJG replacement block is not easy or cheap. If all hope of finding a TA block is lost then one might find an MPJM (Morris) or MPJW (Wolseley) engine block in the UK or OZ were they were more plentiful. These were virtually the same blocks and there were lots more Morris cars manufactured than M.G.s!

Markings Identify The Wolseley & Morris Cylinder Head
MG Head Was Marked [ 10 G ]

Good cylinder heads are also hard to find, most have been skimmed several times and they are prone to crack. But these too may be substituted by using Wolseley or Morris 10 heads. The question of whether or not to cut a head and install hardened seats is always a topic of discussion among TA owners. I chose not to install hardened seats and will use additives and also need to keep my fuel mixture richer than those using them. There's also the question with the early models of using double or triple valve springs. Most now prefer the triple spring set which the later MPJG engines used. But new double spring sets should not have the problems with breaking as a few people experienced back when these engines were new.

Original Non-counterbalanced Crankshaft

The original MPJG used a non-counterbalanced crankshaft. While they are quite serviceable, they can add a bit of stress and unwanted vibration into the block unless all the moving parts are balanced. So it's only common sense to have everything inside the engine balanced. And, after all these years of use, some of our original cranks are likely to be turned to the maximum safe undersize. However, one of the strong points of the MPJG is that by using babbitt (white metalled) bearings, standard regrind dimensions are nonexistent. One can remove the least amount possible from a journal to clean it up and then have the babbitt sized to that journal. Nor do all the journals have to be the same dimension. Just be aware of the balance problem and try to keep everything within reason. New billet counter-balanced crankshafts are an alternative and are available but pricey. If going this route be prepared to make modifications to the block and possibly to the new crank as well (See Phoenix Crank in the menu.) When reusing the original forged crank there's an old method for crack-testing. Hang it from a wire and give it rap with a wrench. If it has a nice bell-like ring then odds are it hasn't any cracks... then go have it magnafluxed.

Billet Rod vs Original Rod

The original rods have a couple of inherent weaknesses. One, is their length -they're so long and skinny- and another is the pinch-bolt method for attaching the pin at little end. Over-revving an MPJG can lead to large holes in the block. One solution is to use new Carrillo-type rods with closed little ends and floating piston pins.

New Old Stock Pistons can often be found for sale on ebay or sourced from one of the suppliers in UK such as Clive Pearson. Mr. Pearson may also have rings to fit your existing pistons if needed. Pistons and rings can also be custom manufactured as a set for reasonable costs from sources like Venolia, JE or Wiseco. And with a bit of research you should be able to find custom sleeves for a block if the cylinders are worn beyond oversized limits.

Newman of Farnborough Cam On Right

New camshafts are available to order through Newman of Farnborough, Kent, England. When considering the timing gears do not re-use gears with sharp teeth! This is a sure sign they're worn out and your timing will never be consistent when using them.

The oil pump can be rebuilt using new gears or improved just by turning the spindle in the block by 180 degrees but the original felt filter system could stand a bit of improvement. I used a Metro A series spin-on filter bracket and modified it to fit on the block. (See Modern Oil Filter in the menu.) This is not going to get you any points with a concours judge but it is a clean and economical solution to filter changes. Packing the pump with a viscous oil (some use Vaseline - I used Lubriplate 105 and motor oil) helps to prime it when you start the engine. I also filled the spin-on filter with oil then pressurized the system using a clean garden sprayer attached at the oil gallery until oil flowed from all the rocker arms. Choosing which oil to use for running in after the rebuild will occupy hours of happy research. If your cam is new or you've only resurfaced the lifters (as I did) or both, then you'll want something with a higher ZDDP count than most of the stuff off the shelf. I used Rotella T 30wt. for running in and the first two oil changes, switching to Rotella T 15-40wt. at 500 miles. There are now several grades of Classic 20W50 on sale for use in flat tappet engines requiring higher ZDDP levels.

Some owners of wet-clutch M.G.s have said that replacing the corks was not difficult for them and I gave it a try. But after spending too much time and not getting very far I chose to have it done professionally. Be sure to get the correct height of the cork (1/8") off the plate on both sides. (See Clutch/Flywheel in the menu.) I'm not sure what the minimum thickness is but if any corks are missing renew the lot. Another clutch factor to contend with is slippery additives in the motor oil. These clutches share the same oil with the engine and synthetics are sure to cause slippage. Steer clear of STP and similar synthetic products.

Considering the heavy weight of the flywheel several owners have lightened them in hopes of getting the engine rpms up faster. Actually its weight adds to the TA's ability to run smoothly at low speeds in higher gears. I decided to lighten mine by about 5 pounds (See Clutch/Flywheel in the menu.) and if there's a difference then it is hardly noticeable. However I'm using a 10 pound heavier than original crankshaft.

The SU carburetors are simple and easily rebuilt by the owner (making sure the butterfly shafts and body are not worn out) and they're also easy to tune once they're put in good condition. The SU fuel pump can benefit from being transistorized and this too is a simple project. A search on the net will produce a number of sites showing how-to examples.

TA Needles

Needles for the TA & VA engines

This abbreviated Service chart gives the diameter of the TA carb needles in 1/4 inch increments measuring down from the shoulder. Needles from MG Type VA engines are included for interest considering that some TAs become Trials cars (Cream Cracker Team) using TPDG engines.

New Viton Front Seal Conversion

The MPJG uses a felt seal in the timing cover at the front of the engine which is prone to weep oil. A new seal kit is now available from Brian Rainbow, UK, consisting of a machined replacement carrier for the timing cover and a new Viton seal. Properly centered, it should eliminate virtually all oil leaks from the front. The MPJG does not suffer the rear seal leak that plagues XPAG owners. Brian also offers an Adjustable Oil Pressure Valve. I'm running both and consider each a worthwhile improvement.

A number of businesses offer water pump rebuilding. Select your rebuilder with care. (See Water Pump Repairs in the menu.) Inquire whether or not they are modifying the body of the pump. Some mods may render the pump no longer usable with the original carbon seal. Then again, the original seals are no longer available! Bob Butson, of Wales, has written a comprehensive article (Click HERE to view.) which details the disassembly and repair of his TA water pump. It is well worth reading and might just save you from destroying a reusable carbon seal.

The Octagon Car Club is a good source for many MPJG items and may still have new cam gears, timing chains, etc. but for some absurd reason may no longer be shipping to anyone in the USA. Pity. NTG also in UK is another source. They have gasket sets and a number of other items and sell on eBay. Other eBay sellers in UK stock engine torque straps, rocker shafts, pistons, rings and valves etc. Rebabbitting can be still be sourced in most larger cities by machine shops catering to classic and antique automobiles. Occasionally individuals will offer used MPJG items on eBay but understand how old these bits are. The likelihood of getting a 'like new' item is slim... but not impossible.

For a rebuild you'll need good set of Whitworth/BSF sockets and wrenches. And a torque wrench but be aware that there are no 'factory sanctioned' torque settings! Be sure to clean all the bolt holes using the proper taps prior to replacing or using new bolts. These are Metric threads and not Whitworth. BSF/Whitworth heads on metric fasteners... Mad Metrics! You'll need Taps and Dies of; 8 x 1mm and 10 x 1.5mm. New nuts and bolts can be sourced from Roger Furneaux in UK. Other items might be had through Doug Pelton in USA.

The last item to mention would be the first needed before rebuilding an MPJG engine. A Manual. No, several manuals. For starters you should have The MG TA Midget Instruction Manual. Then when you're ready to get your hands greasy, W. E. Blower's The MG Workshop Manual and Philip Smith's Tuning and Maintenance of M.G.s. Both are great references as well as The T Series Restoration Guide by Malcolm Green. And a copy of The Service Parts List for the MG Midget (Series TA and TB) is always helpful.

Finally... Join an Internet forum!!

Thanks to Ian, Brian, "Bob", Bob, Roger, Alan, and many others offering help and advice on rebuilding my engine.

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B Davis.