Holden Engine Conversion
This is quite a long topic so it is spread over several pages.
Before you begin (on this page)
The practical value of the Holden Six conversion (on this page)
Points to consider when contemplating the conversion (on this page)
The cost of my own conversion (in a separate document)
Choosing the right Holden motor (in a separate document)
Before you begin.
This page will be of most interest to Australian readers because it deals with the
transplanting of the locally produced Holden "red" Six into a Series Land Rover.
The famous Holden "red" motor made its first public appearance in August 1963
and endured in various guises for the next twenty three years. It was designed at the
Warren, Michigan tech centre of General Motors in the early sixties by a team of
Australian and American engineers. Many of the American team members had also worked on
the Chevy engine project which first appeared as a 194 in the Chevy Nova of 1962. There
are some visual similarities between the Chevy sixes and the Holden red motor but they
have hardly a dimension in common and the Holden is unique to Australian built General
Motors-Holden cars. Therefore the Australian made conversion kits WILL NOT WORK with any
of the family of American built Chevy sixes.
This is not a cheap way of extending the life of an old Series Land Rover with a dud motor. A well used Holden motor salvaged from Uncle Freds rusty old Kingswood will not magically rejuvenate your Rover for just the cost of the conversion kit. The kit itself is not exactly cheap and unless you are prepared to do it properly, the conversion is not worth the effort and the money would be better spent on fixing the Land Rover motor.
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The Holden
conversion is practical for the following reasons.
They are a larger capacity six cylinder motor, better able to maintain highway speeds on modern roads and with torque characteristics suitable for off-road use.
Rebuildable core motors are readily available, often for next to nothing. Holden motors are well understood by mechanics and any "red" motor presented to a reputable engine reconditioner will come back to you rebored and with every moving part replaced or reconditioned for less than $1000 including labour. You can do it yourself for less if you have the time to dash about taking blocks, heads and cranks to and from machine shops.
Spare parts for routine maintenance or for a midlife ring and bearing job are inexpensive and readily available. The water pump for instance is an easily replaced throw-away item for about $30. Starter motors and alternators are stock exchange items as are cylinder heads.
The conversion job is particularly easy on the 109" six cylinder chassis. Unless you want to keep the Land Rover 2.6litre six for sentimental or historical reasons, the Holden six is an ideal replacement which feels very similar to drive but without the problems associated with the Land Rover motor. If everything continues to work correctly, you need never worry about burning valves on a Holden motor because it is equipped with self adjusting hydraulic tappets.
It is possible to revert back to an original motor as no irreversible changes are made to the structure of the Land Rover.
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Points to consider when contemplating the conversion.
Gearbox: You will have up to twice as much horsepower as a Land Rover 2286cc four. If your Land Rover transmission was showing any signs of age before, a fresh motor with more power will accelerate its demise. Series Land Rover gearboxes are a 1930's design and even a rebuilt one can be destroyed by habitual clutch-dropping and power shifting. Your Series gearbox invites deliberate shifting, especially the non-synchro IIA ones, so cultivate a relaxed driving style. The Holden motor was commonly found in family sedans with three speed manual gearshifts and its flexibility is its greatest asset for service in a Land Rover.
Clutch: Adaptor kit manufacturers in the past have tried to make do with the stock Holden flywheel and Holden clutch with disappointing results. Marks Adaptors have a new flywheel which bolts right onto the Holden motor. It is drilled and dowelled to take either diaphragm or coil spring Land Rover pressure plates and the ring gear suits the Holden starter motor. You should treat your Holden Rover to a new clutch plate and at least examine the pressure plate.
Engine Mounts: There is no need to cut off and move the mount brackets on the Land Rover chassis. They stay where they are and the Marks Adaptors brackets which bolt to the engine line up with the chassis brackets. Land Rover mounting rubbers are used. The square diesel mounts transmit more vibration but are reputed to last longer than the noraml round rubbers. You will have to retain the Land Rover electric fuel pump on six cylinder models as the righthand engine bracket design used by Marks Adaptors does not leave room to fit the Holden mechanical fuel pump. If you were really desperate to have the Holden mechanical pump you would have to move the righthand chassis bracket back and modify the engine bracket. However, this would make the conversion more difficult to reverse.
Exhaust System: This is hard to comment on as there were so many types of Land Rover exhaust system and so many Land Rovers getting about with non-stock systems. As a minimum, you will need an engine pipe bent up to suit your Holden exhaust manifold and your existing intermediate pipe. I suspect that a stock four cylinder LR silencer would be unduly restrictive for a Holden motor. You may need the services of a competent exhaust fitting workshop.
Overall gearing: Holden motors weren't made to run near peak revs for long periods of time. A stock Series drivetrain is definitely undergeared for a Holden six. It is essential to raise the overall gearing by some means so as to take advantage of the strong mid-range power and avoid revving the thing to death. See my Transfer Case Conversion pages for details of my favourite method and some other alternatives.
Legality: To be legal and insurable, your conversion will need to be inspected by the appropriate authority. In Queensland it is done by an Authorised Officer of the Queensland Transport Department. The Department knows all about Landrover engine conversions and has simple guidelines which mostly concern the braking equipment. Briefly, you can fit anything you like up to 4 litre capacity provided the brakes are upgraded to Series III vacuum assisted specification. Any chassis or body modifications need to be done in a workmanlike fashion. Any emission control equipment originally fitted to your new motor must be in place and in working order. You should check up on the rules in your own State to see what you must do to comply.
The emission control question is particularly important as post 1976 motors made to comply with the ADR27A emission regulations can best be described as dogs. They were strangled by a mild cam and restricted ignition advance controlled by bolt-on engine sensing systems. The basic block and head are exactly the same as before and can be built up with pre-1976 cam and ignition systems. However, an unsympathetic or just conscientious inspecting officer may refuse to pass a block carrying a post-1976 engine number which lacks any of the specified emission control systems.
See Choosing the right Holden motor for guidance.Brakes: As I said before, the conversion is particularly easy in a Series IIA/III six cylinder109 chassis. The Series III 109 will already have a directly coupled Girling vacuum brake servo mounted on the pedal box assembly while the IIA 109 may have a PBR remote in-line servo, depending on its age and model. The rather tidy looking Series III pedal box assembly will bolt directly into a Series IIA in place of the original pedal box with some trimming of the inner top edge of the wing to clear the booster.
To upgrade an 88 to Series III vacuum assisted specification you will need a Series III pedal box assembly, a vacuum servo and a 7/8" CV master cylinder rather than the 3/4" master fitted to the non-boosted 88.
The 10 inch brakes fitted all round on an 88 are within the Queensland specifications if vacuum boosted and I would be wary of upgrading them to 11 inch 109 types for fear of over-braking the lighter vehicle.
On the other hand, the twin leading shoe 2.25 inch wide by 11 inch diameter drums on the front of a 109 can usefully be upgraded to the full 3 inch wide linings and drums found on the Series III Station Wagon and one tonner. You will need new drums, linings and backing plates. The brake cylinders are the same.Cooling: A Holden six will fit straight into a six cylinder 109 chassis without fouling the radiator. The four cylinder 88 or 109 chassis has the transmission mounted about 70mm further forward than in the six cylinder 109. Therefore the cooling fan on a Holden six will foul the radiator core unless the radiator is moved forward.
The bottom tank of the stock Land Rover radiator comes down lower than the crossmember which carries the steering relay.
The crossmember can be "notched" to a little more than the width, depth and thickness of the Rover bottom tank and the sides and bottom of the notch plated up with 1/8" steel. The vertical front face of the crossmember is left in place and reinforced with more plating. This can be very neatly done but will require removal of the radiator support panel and wings to allow unrestricted access with cutting equipment and welder.
Alternatively, a wider shallower radiator, possibly a crossflow type, can be adapted to sit on top of the crossmember. It may even be possible to source a custom made one, (at a price), if you can arouse the interest of an experienced person in a radiator workshop.
In my view, the stock Land Rover radiator is capable of cooling a Holden six if it is in good condition. If it was doubtful when cooling your Rover motor it definitely won't be adequate for the Holden. Repair or replace if it has a million miles of service behind it. The four cylinder Land Rover radiator has a centrally located top hose spigot which matches the Holden motor better than the six cylinder spigot on the left. The right mounted bottom spigot is common to both radiator types which appear to be identical in core size. The radiator hose spigot on the Holden thermostat cover should be an upwards-pointing Holden Torana type rather than the sideways type seen on the full sized family cars.
The hose spigots on the Holden motor may not match the diameter of the spigots on your Land Rover radiator. Fortunately, flexible universal hoses are readily available with different i.d. at each end. Dayco or Gates brand made in America are good. Carefully measure your spigot sizes and hose lengths and visit a large hose supply warehouse. Buy two spare hoses while you're at it and carefully write down the part numbers in your Land Rover record book. You may not find your hose size in some Outback service station.
Finally, don't forget to fit a new 15lb radiator cap to suit your Holden motor.
Oil Cooler: I am not sure whether these are strictly necessary. However, the Australian military spec six cylinder Series III had them and I don't think that it does any harm to fit one to a Holden motor. They have less than a gallon of sump capacity (4.2 litres) compared with the 12.5 to 13 pints of a Land Rover motor and will benefit from the additional cooling.
I used a Lynx brand oil cooler adaptor which sandwiches between the spin-on filter cartridge and the filter sealing face on the oil pump casting. The cooler was made by Perma-Cool, The Leader in Performance Cooling, or so they say, in the USA. Consult your local performance parts supplier for advice. With a sandwich adaptor, a Z30 Holden six filter is a very tight fit. Try the shorter Ryco Z97A as used on Range Rover motors or the Ryco Z160 from the Holden Commodore V8s. The Z160 is much shorter and needs to be changed with every oil change. Both these alternate filters were recommended by a consultant on the Ryco telephone hot-line.Engine Oil Pan: The shape varies with the model your core motor came from. Some had the deepest portion of the pan towards the front of the motor. This sort will come perilously close to the front differential. You should change to a pan with the deep part towards the rear of the motor. You will need the appropriate oil pickup and strainer assembly and the right dipstick tube. I nearly got caught once when having a motor rebuilt. I happened to mention that it was going into a Land Rover and the alert reconditioning workshop foreman immediately said that it would need a different oil pan. He supplied used parts from the HR/HK/HT model series at no extra cost. Top marks for that foreman! I'll deal with his firm again.
The incorrect pan had the oil dipstick tube welded into the side towards the front. The substitute pan had none. However, the engine block has a rubber-bunged hole just behind the oil pump intended for a dipstick tube when a rearwards type pan is fitted. They forgot to supply the dipstick tube which is a tight push-in fit. I found a suitable piece of steel tube. Then I filled oil filter and sump with exactly the amount of oil specified in the manual. I noted where the oil level came to on the dipstick and trimmed the dipstick tube to the right length by the cut and try method. If changing the pan on your motor it could be worth checking the accuracy of the dipstick.
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