Wolseley 4/44
Engine Re-build and Tuning
using Moss Motors MG TD / TF components

Tuning the MG XPAG / Wolseley XPAW

XPAG / XPAW Stage 1

A standard rebuild with a bit of port work and some extra compression.

Raise compression ratio to 8.6:1 by removing 3/32" off cylinder head face. Standard head is 3.0177" (76.75mm) thick; finished thickness after machining is 2.928" (74.37mm).
Polish, but do not grind out the combustion chambers. Make sure the gasket edges do not overlap the combustion chambers.
The ports may be ground and polished, but should not be ground out so heavily that the shape or valve choke is impaired. The inlet port outer separating stud boss may be ground away slightly - about 1/16" off each side so that oblong ports are obtained, 1 3/16" high x 21/32" wide (minimum). Do not remove the boss completely or it will affect mixture distribution.
Match up by grinding all inlet and exhaust ports with the manifold ports. Grind out and polish the inlet manifold, also matching the carburetor bore.

• Use standard cylinder head gasket
• Use 3/32" thick x 3/4"OD washers under cylinder head nuts (to correct for reduced head thickness)
• Use 4 rocker-shaft stand packing pieces (Moss No. 433-128) under base of the rocker stand to correct rocker adjustment (1/16" mild steel with 3 oil holes matched to the stand base)
• Re-jet the 1 1/4" SU(s)
• Use a Hi-Energy Coil
• Plugs - Champion L.10.S / Lodge R.49 for ordinary work or Champion L.A.11 / Lodge R.49 for high speed work.
• Ignition Timing - TDC static - (ie not by timing light as there will be advance present if the motor is running).

Distributor

Standard assembly - rebuilt to factory spec. Set timing to TDC static - (ie not by timing light as there will be advance present if the motor is running). For other options, see the distributor section below.

XPAG / XPAW Stage 1A

A standard rebuild with a bit of port work, larger valves and some extra compression.

Raise compression ratio to 8.6:1 by removing 3/32" off cylinder head face. Standard head is 3.0177" (76.75mm) thick; finished thickness after machining is 2.928" (73.575mm).
Polish, but do not grind out the combustion chambers. Make sure the gasket edges do not overlap the combustion chambers.
The ports may be ground and polished, but should not be ground out so heavily that the shape or valve choke is impaired. The inlet port outer separating stud boss may be ground away slightly - about 1/16" off each side so that oblong ports are obtained, 1 3/16" high x 21/32" wide (minimum). Do not remove the boss completely or it will affect mixture distribution.
Match up by grinding all inlet and exhaust ports with the manifold ports. Grind out and polish the inlet manifold, also matching the carburetor bore.

• Use standard cylinder head gasket
• Use larger Inlet valves - (Moss No. 423-010 1 5/16" )
• Use larger Exhaust valves (Moss No. 423-020 1 3/16" or 423-025 1 3/16" stellite faced)
• Cut away combustion chamber wall to clear valve heads.
• Bore out valve choke to match valves - not the same size as the valve head!
• Recut valve seat to 30 degrees
• Use 3/32" thick x 3/4"OD washers under cylinder head nuts (to correct for reduced head thickness)
• Use 4 rocker-shaft stand packing pieces (Moss No. 433-128) under base of the rocker stand to correct rocker adjustment (1/16" mild steel with 3 oil holes matched to the stand base)
• Re-jet the 1 1/4" SU(s)
• Use a Hi-Energy Coil
• Plugs - Champion L.10.S / Lodge R.49 for ordinary work or Champion L.A.11 / Lodge R.49 for high speed work.
• Ignition Timing - TDC static - (ie not by timing light as there will be advance present if the motor is running).

Distributor

Standard assembly - rebuilt to factory spec. Set timing to TDC static - (ie not by timing light as there will be advance present if the motor is running). For other options, see the distributor section below.

XPAG / XPAW Stage 2

With the exception of the distributor and carburetor choice, all engine changes are internal and will not be visible when looking in the engine bay.

Raise compression ratio to 9.3:1 by removing 1/8" off cylinder head face. Standard head is 3.0177" thick; finished thickness after machining is 2.8966".
Polish, but do not grind out the combustion chambers. Blend in the sharp edge at the sparking plug hole. File this edge back vertically until it is a minimum of 1/32" at the center. Blend it in for a radius of 1/2" wide scope. Make sure the gasket edges do not overlap the combustion chambers.
The ports may be ground and polished, but should not be ground out so heavily that the shape or valve choke is impaired. The inlet port outer separating stud boss may be ground away slightly - about 1/16" off each side so that oblong ports are obtained, 1 3/16" high x 21/32" wide (minimum). Do not remove the boss completely or it will affect mixture distribution.
Match up by grinding all inlet and exhaust ports with the manifold ports. Grind out and polish the inlet manifold, also matching the carburetor bore.

• Use standard cylinder head gasket
• Use larger Inlet valves - (Moss No. 423-030 1 7/16" / 36mm)
• Use larger Exhaust valves (Moss No. 423-040 1 3/8" / 34mm or 423-045 1 3/8" / 34mm stellite faced)
• Cut away combustion chamber wall to clear valve heads.
• Bore out valve choke to match valves - 33mm below the inlet valve, seat recut to 34.9mm top diameter, recut valve seat to 30 degrees. 29mm below exhaust valve, seat recut to 32.8mm, recut valva seat to 30 degrees.
• Fit heavier valve springs (Moss No. 423-410 or 423-420 - if staggered pitch wound springs - closed coil ends are next to the head)
• Use 1/8" thick x 3/4" OD washers under cylinder head nuts (to correct for reduced head thickness)
• Use 4 rocker-shaft stand packing pieces (Moss No. 433-128) under base of the stand to correct rocker adjustment (1/16" mild steel with 3 oil holes matched to the stand base)
• Use a 1 1/2" SU or a 1 1/2" Hitachi SU copy from a Datsun / Nissan 260 Z (2 of each for the XPAG)
• Plugs - Champion L.A.11 / Lodge R.49
• Ignition Timing - TDC static - (ie not by timing light as there will be advance present if the motor is running). See the distributor section below.
• Obtain and install the full circle rear main seal and front seal conversion. As the crank has to be machined to install the rear main seal kit, fit the conversion during the rebuild.
• Engine oil - change oil and filter every 3,000 miles. I use a 10W40 full synthetic oil.

Camshaft

XPAW - Reground / re-profiled standard Wolseley XPAW cam - 18/58 - 58/18 degrees inlet and exhaust with rockers set to 10 thou. inlet and exhaust - HOT. Very quite running rocker gear. Take the advise of the cam grinder as to running in and valve running clearances.

XPAG - There are many choices available for the MG engine that are not suitable for use with the much heavier Wolseley. Moss Motors offer 451-260 (standard grind) or 451-270 (3/4 race). Any MG T specialist will be able to recommend a suitable grind to match the engine changes.

Distributor

For options, see the distributor section below.

XPAG Stage 3

Raise compression ratio to 12:1 by fitting special high compression 12:1 pistons. Use with standard head of 3.0177" thick. The pistons can only be fitted one way round - that is, with the flame groove on the sparking plug side
Match up by grinding all inlet and exhaust ports with the manifold ports. Grind out and polish the inlet manifold, also matching the carburetor bore.

• Use standard cylinder head gasket
• Re-jet the 1 1/4" SU(s)
  Use GK needles - RC richer and RV weaker
• Use Float-chamber needle and seat assmeblies SU type S3
• Use 2 SU petrol pumps for increased delivery
• Fuel: 80% dry blending methanol SG .796 at 70 degrees F
  10% benzol SG .8758 at 60 Degrees F
  10% petrol - 70 to 80 octane
  1% castor oil
• Use a Hi-Energy Coil
• Plugs - Champion L.A.14 / Lodge R.49.
• Timing - start at 4 degrees ATDC and tune from there.

XPAG Stage 3a

• As for Stage 3 above, plus:
  Fit 2 x 1 1/2" competition carburetors, SU specification 578; (.100 bore jets, .125 bore jets or .1875 jets). Match bore to inlet manifold. It is not possible to grind right through at 1 1/2", but it is necessary to taper off in about a 3/4 length to 1 3/8" diameter. Maintain a minimum of 1 3/8" right through. These carburetors will be found to be fitted with light aluminium pistons with additional springs fitted above the dashpot. For absolute power, these springs may be removed, but for good pickup and smooth running should be left in place.
• Fit .125 jets, VE needles - VG richer and VA weaker
• Fit larger Inlet (36mm MG862/460) and Exhaust (34mm MG862/461) valves with 150 pound springs (MG862/462 plus MG862/463)
• On same fuel as Stage 3 this engine should produce 80BHP at 6,000 RPM
• Using 100% Methanol, .125 jets, VJ needle (VL richer, VI weaker) the engine should give a maximum output of 83 BHP at 6,000 RPM.

Distributor - 4 choices

Where fitted, test the vacuum advance unit is fully functional - no holes in the diaphram and no binding on the points plate. See table further down this page for a Lucas BMC distributor characteristics table.

Standard assembly - rebuilt to factory spec. Set timing to TDC static - (ie not by timing light as there will be advance present if the motor is running). Test the vacumm advance unit is fully functional - no holes in the diaphragm and no binding on the points plate.

Standard assembly - modified to replace points with pointless electronic ignition. Set timing to TDC static - (ie not by timing light as there will be advance present if the motor is running). Use a Hi-Energy Coil (Bosh GT40 or similar)

Mini Cooper S centrifugal advance - 15 degrees on the crank or 30 degrees total advance - either points or convert to full electronic. Plug the vacuum line at the carburetor. Swap the drive gear (the drive for A & B series motors is different to the XPAG/W). Set ignition to TDC static or 5 degrees BTDC at idle, with a timing light. Use a Hi-Energy Coil (Bosh GT40 or similar)

Honda Civic (1980 - 1983) EN1 engine full electronic distributor. Almost a drop-in replacement for the Lucas. Requires electronic module as well as the distibutor and cap.
Modify by machining 2 mm from the body length (the section that goes into the engine block) and reduce the drive shaft length by 20mm. Swap the standard Lucas drive gear to the shortened shaft; drill shaft and pin gear in place. Either modify the Lucas clamp or the Honda clamp can be modified to suit. This distributor rotates counter-clockwise and has nearly an identical advance curve to the Cooper S distributor. Use with high energy coil. Set ignition to TDC static or 5 degrees BTDC at idle, vacumm advance plugged, using a timing light.

Diff. Ratio

Standard Wolseley 4/44 ratio is 5.125:1, the Wolseley 15/50 is 4.875:1 and the MG Magnette is 4.5:1. The Magnette assembly is easier to find (in Australia) and has has larger brakes. If the Magnette rear end is installed, install the Magnette front hub / brakes as well to keep the braking balanced. MGB diff's (3.9:1) can be fitted to the Magnette but this ratio would be too tall for the 1250cc Wolseley (unless it were supercharged). A Stage 2 engine can pull the 4.5:1 ratio but hills represent a challenge (you will have to down-change more often on hills) but the resulting drop in rev's, engine noise and fuel consumption at 60MPH makes the change worthwhile.

Owners view of the "Hot" XPAW.

After 4 years running, I can recommend the TC /TF rebuild/upgrade to any 4/44 owner. I built my engine to Stage 2 specifications with a Cooper S distributor and a single new 1 1/2" Hitachi SU. The Hitachi is supplied for Morris Minor conversions - brand new it cost me A$120 plus and adapter. I could not source a new SU in the time frame I had to get the engine operational, and, as the Hitachi works so well, I have not bothered to change it.

The Cooper S distributor was installed after months of overheating problems. At first I thought that the internal changes to the motor had increased the operating temperature of the engine beyond the capabilities of the radiator, fan and water pump. My Wolseley 1500 has a 1620cc engine that also got hot after a hard run on the freeway. When the 1500 died with a blown head gasket the answer became obvious - no advance available when the vacuum diaphragm has a hole in it! Couldn't get hold of a replacement, but was advised the Cooper S centrifugal advance distributor is a direct drop-in replacement that would solve the problem for all time - no more holes. Fixed the 1500 and then confirmed the same problem existed with the 4/44. Bit more to the conversion on a 4/44 (you have to change the drive gear) - but end result is the same - no more overheating.

Final Verdict - DO IT!

If your Wolseley 4/44 is in need of a rebuild and a few extra ponies, drop by the nearest MG T specialist and relieve him of the necessary bits to make a truely worthwhile rebuild. You can build as mild or as wild as you wish. Using the Stage 1 or 1A option will extract that little bit extra from the available fuel, while Stage 2 will completly change you view of the abilities of a Wolseley 4/44 without resorting to twin SU's and other more obvious engine changes. In either state of tune, it is unlikely you will wear the engine out in your lifetime. Also remember, you can build a Stage 2 engine with the lower CR of Stage 1 - as lower octain fuels become normal, this could be a sensible choice. In any rebuild, I would strongly recommend installing the full circle seals on both ends of the crank to stop most of the oil leaks at these points.

Just for the record my XPAG Wolseley 4/44 engine has the following:

Stage 2 tuning using the following -

• Hepolite RS14136 66.5mm +.5mm (20 thou oversize) flat top 4 ring pistons
• -10 thou bearings on a reground crank
• CAM - 18 BTDC, 58 ABDC - 58 BBDC, 18 ATDC
• 1 7/16" (36mm) TF MKII inlet valves
• 1 3/8" (34mm) TF MKII stellite faced exhaust valves
• 1/8" off cylinder head face for 9.3:1 compression
• Mini Cooper S centrifugal advance distributor with Bosh GT40 coil
• Hitachi 1 1/2" SU
• Full circle seal kits on both ends of the crank
• Bigger bore but still very quite exhaust

According to the 'Special Tuning for MG Midget Engines' Guide - for a Stage 2 XPAG engine with twin 1 1/2" Carb's, this should result in 65BHP at 5,500 RPM - better than standard 1500cc B Series motor. Although BHP for the single 1 1/2" carb. XPAW will be lower, it is still a substantial improvement. In the near future I plan to install a Magnette diff and brakes.

John Miller
Wolseley Car Club of Queensland Inc.

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Lucas Distributor Specifications:

Not the different advance curves for the different models - wrong choice of weights, springs and vacumm advance units (wrong mix and match of units) can really harm the performance of an otherwise well built engine.

The curve of a Cooper S distributor will have full advance 'all in' much sooner than the 4/44 distributor. Standard 4/44 distributor gives 17 to 19 degrees centrifugal and 7 to 9 degrees vacuum - total advance of 28 degrees. The Cooper S has a total of 30 degrees. Be very careful setting the static firing point to TDC so as not to give the engine too much total advance.

Further reading:

The Wolseley Four-Forty Four Workshop Manual. BMC part Number AKD738D.

Tuning and Maintenance of MG Cars - Philip H Smith ISBN 0 85429 098 2 First edition 1952, Reprinted, '53, '54, '55, '56, '69, 71 and 1978. Published by Haynes Publishing Group.

Tuning the A-Series Engine - David Vizard. I don't have a copy for the ISBN number. However, this is one of the best sources of information on BMC engines - translates well to XPAG/XPAW, directly relates to all A-Series (Mini) and translates to all B-Series. Covers theory of engine operation and background to modifications - cam selection, compression ratios, SU's...... If you don't have a book on tuning small 4 cylinder engines - buy this on.

Hitachi SU Tech. reference http://www.jetlink.net/~okayfine/sutech.html

Moss Motors USA http://www.mossmotors.com

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