• VAUXHALL - THE SLANT FOUR ENGINE STORY
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A CUTAWAY OF THE NEW OHC ENGINE ON DISPLAY AT THE 1967 LONDON MOTOR SHOW

One of the most expensive aspects of designing and manufacturing a completely new car is the investment required for a new power unit. In addition to straight forward requirements such as power or torque characteristics consideration must be made for current and, more importantly future, exhaust and noise emissions plus fuel consumption legislation, ease of maintenance and durability. Then there is the fixed costs of production such as machine tools, casting moulds etc. General Motors are no different to any other global car maker by being able to offset these huge investments far quicker than before by ensuring one engine range can be used in virtually every part of the world market in a multitude of different cars. This procedure means that engines can be replaced every 5 to 8 years or at least be extensively modified. In the past this life expectancy would have been anything up to 20 years, in some cases even more, because of the way the industry, and GM, worked back then – globalization had not really started.

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JOHN ALDEN, VAUXHALL ENGINEERING DIRECTOR, PHOTOGRAPHED IN 1968 WAS AN IMMENSELY TALENTED ENGINEER & CAPABLE LEADER OF HIS DEPARTMENT. ALDEN WAS THE MAIN PROPONENT OF THE SLANT FOUR ENGINE PROJECT

When John Alden took over from Maurice Platt as Vauxhalls Chief Engineer in 1963 it was becoming clear that the 1508cc mid-range engine used in the FB Victor and VX4/90 was coming to the end of its competitive lifecycle. There would be one more revision to increase power and torque by an enlargement in size to 1594cc to be used in the last of the FB series and ready for the FC Victor 101 and its VX4/90 stable mate. Due to the lack of space between bore centres and water jacket dimensions the engine could not be significantly increased in capacity any further and in addition Vauxhall had a yawning gap in their engine line up, the next step up was the 3.3 litre six cylinder engine. What Vauxhall needed was a range of engines from 1500cc to 2000cc.

Alden was noted for exploring unconventional ways of doing things, he was responsible for the forward control Bedford TK which was revolutionary when launched in 1959, so it was no

surprise that he proposed a more radical approach to the new engine development by proposing that a whole engine family could be created using the same production tools and transfer machining as well as internal components. This way the production costs could be spread across a wide range of models including Bedford commercials. Here is the 4 stage story of how the slant four engine evolved:

STAGE I:

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A CUTAWAY DRAWING OF THE FIRST PROTOTYPE SLANT FOUR OF 1737cc FIRST TESTED IN SEPTEMBER 1964, A TOTAL OF SEVEN WERE BUILT

Plans were mapped out by draftsmen in the drawing office of the Design & Engineering Department in February 1964 then the blueprints were passed to the machine shop and in September 1964 the first experimental engine was up and running on a test bed. This first engine had a single chain-driven overhead camshaft. It had four cylinders, five main bearing, a bore of 3 1/2ins and a stroke of 2 3/4ins, giving a capacity of 106cu.ins.(1737cc) A combustion chamber was provided in the piston crown, and the design incorporated a cross-flow head to facilitate high speed running. The whole engine was inclined at an angle of 45 degrees to the vertical to reduce overall height and fitted in with plans for the V8 versions. The block specially stiffened at its rear to strengthen the engine bell housing joint. Structural materials were entirely cast-iron, as the new "thin-wall" casting techniques were just beginning to be developed for production by GM in the US, and the weight savings by using alloy was not considered worth the extra cost involved despite having been used on the head of VX4/90 versions of the FB & FC. In total seven of these 1737cc test engines were built.

STAGE II:

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A CUTAWAY DRAWING OF THE SECOND PROTOTYPE SLANT FOUR OF 1835cc , A TOTAL OF FOUR WERE BUILT

Many of the revisions made to the Stage 1 engine were necessary to develop from an engineers "brain child" into production feasibility - others were to improve reliability, ease of maintenance and to achieve desired power output. The Stage II version had a slightly larger capacity - 112cu.in (1835cc) having a bore of 3 5/8ins and a stroke of 2.726ins and first ran in April 1965. This engine retained an integral cylinder head and camshaft housing. The chain drive was discarded in favour of toothed belt made from glass-fibre-cord tension member with Nylon/ neoprene teeth at 1/2ins pitch. The designers determined that the chain driven method would require careful attention at roughly 20,000 mile intervals to ensure they remained reasonably quiet, as had been proved in the Viva 1159cc OHV unit, while the rubber-toothed belt type were then just beginning to become available, first launched by Pontiac in the US. Nevertheless, the rubber belts had many advantages, they were quiet and housings for it did not have to be incorporated within the engine itself, OHC cylinder heads could be designed that could be simply turned back to front and used on the right bank of the V8. The belts were incorporated in the second phase of development engines. Three test rigs broke but not one belt, in fact even after 2000 hours running at maximum speed there was only a 0.007 in. of permanent set.

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AT THE TIME A TOOTHED BELT DRIVING THE CAMSHAFT WAS REVOLUTIONARY FOR A HIGH VOLUME PRODUCTION CAR LIKE THE FD VICTOR

THE VAUXHALL PATENTED SIMPLE SCREW WEDGE TAPPAT ADJUSTMENT THAT HAD TAKEN TWO YEARS TO DEVELOP AND THAT WAS ESSENTIAL FOR A HIGH VOLUME OHC PRODUCTION ENGINE. IT WAS LATE ADOPTED BY GENERAL MOTORS CHEVROLET DIVISION FOR THEIR VEGA OHC ENGINE

The Stage II engine incorporated Vauxhall patented adjustable "inverted bucket" tappets and a conventional distributor driven from an auxiliary shaft. The pistons in the Stage II engine had the same combustion chamber in the crown as in the Stage I engine. It was the decision to do away with this idea which led to the Stage III engine. The reason for the decision was after considerable investigation it was realised that one of the main sources of unburnt hydrocarbons being emitted with the exhaust gasses into the atmosphere comes from the very thin layer of mixture on the the combustion chamber walls being cooled too much to burn, and the surface area of the combustion chamber should therefore be reduced to a minimum. A total of 4 Stage II engines were built and tested.

STAGE III:

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THE STAGE 3 ENGINE FIRST RAN IN DECEMBER 1965

This engine was developed from an inverted hemispherical shaped combustion chamber located in the cylinder head, shaped to provide a minimum surface to volume ratio. The combustion chamber was made as near a perfect segment of a sphere as could be arranged, with the large diameter in-line valve heads carving off two flats. Flat top pistons were now used. The belt drive for the camshaft was retained and had proved very successful in testing. It was during work on emissions that precise control of combustion chamber volumes and spark timing became necessary, in conjunction with AC Delco an extremely rigid, wide-based distributor mounting was incorporated to prevent timing variations from shaft flexing and waggle (as had plagued the ohv Viva engine distributor) and minimise spark "scatter" at high engine speeds. The Stage III engine continued to use the patented tappet adjustment which had also proved successful in extensive tests. This engine first ran in December 1965 and a total of 6 were built.

STAGE IV:

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THE STAGE 4 ENGINE WAS THE FINAL PATTERN FOR THE PRODUCTION ENGINE AND AN INITIAL PRE PRODUCTION RUN OF 32 WERE MADE FOR EXTENSIVE TESTING

Only detail refinements were made to produce the stage 4 engine, of which 32 were made on a pre-production run basis for large scale testing. All the production slant four engines stem from this engine. This testing included static test rigs and dynometers as well as being tested on the road where the engine was fitted into modified FC Victor 101 mules. And so by the spring of 1966 the design of the four cylinder petrol was finalised. The block was cast in high-grade chromium iron with the crankcase split on the centre line of the crank, stiff webs supported the five main bearing housings (as a diesel bottom end was to be fitted on all engines), which were fitted with white metal shells on the 1600 and heavy-duty copper-lead on the 2000. Special attention was paid to the bore finish to make it fully compatible with the type of piston rings, and the cylinder walls were honed to a carefully controlled pattern. At the rear of the block the clutch housing was cone shaped, and heavily stiffened inside with webs to reduce unwanted vibration.On the 2000 engine a mounting for the 3.5 in. diameter pre-engaged starter was bolted to an adaptor below the crank centre line. On the right hand side at the front of the block a very stiff integral support formed a rigid platform for the distributor and a housing for the oil pump assembly. The fact that it was mounted so high in the block was also the reason for the fact that the engine always rattled for a few seconds on start up, but it was also there to facilitate the V8 versions being planned. The same crankshaft was used on both versions of the engine, the bore size being enlarged by 9.5mm in the bigger unit. The crank was cast from spheroidal graphite iron and dynamically balanced. There was a generous overlap of the big end and main bearing journals for extra rigidity; counterweights were arranged on a three-plane scheme. Connecting rods were specially developed from steel forgings with normal H section and a horizontal split at the big end, secured by set bolts. Gudgeon pins were sweated into the little ends by induction heating. There was provision for an oil jet to squirt from a small hole on the shoulders of each big end each time it passed the main oil gallery in the crank journal to provide lubrication for the little end and cylinder walls.The pistons were made from die cast aluminium with solid skirts and three rings all above the gudgeon pin. The upper two compression rings were made of cast iron, the top one being inlaid with molybdenum and the lower one stepped internally. The oil control ring below is of 3 piece construction, with a thin rail on each side of a spring spacer. The pistons have flat crowns with a slight nick to provide clearance should the valve timing go wrong for some unlikely reason. The cylinder head too was made of cast iron, the valves arranged in-line at an angle of 6 deg. to the cylinder centre line.The hemispherical combustion chambers were fully machined to give a smooth finish and to equalize their volumes. The valves were arranged alternately to give an even temperature distribution and they were as large as the combustion chamber allowed. The hemispherical shape was machined away to relieve valve masking on the outer edge at each side and the spark plug was positioned as near the centre of the chamber as possible.The inlet valves were one-piece silchromel forgings, and the exhaust valves had austenitic steel alloy heads with a hardened stellate insert for the seats, and carbon steel stems hardened at the tip. Double valve springs had normal single-groove cotters for their caps, the seat angle being 45 deg. and the valve guides being machined directly into the head. This also meant that valve bounce would not occur until 9000 rpm!!!

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A CUTAWAY OF THE FINAL PRODUCTION VERSION OF THE VAUXHALL SLANT FOUR OHC ENGINE WHICH WAS INITIALLY AVAILABLE IN 1599cc AND 1975cc SIZES

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A SIDE VIEW OF THE SLANT FOUR OHC ENGINE

Because the design parameters were set for the slant four that would allow for the diesel and eight cylinder versions the bottom end had to be endowed with enough strength for the V8 diesel; and the block had to be adapted, for both diesel versions required thicker cylinder walls (ie longer stroke) within the petrol crankcase envelope and it is this design inheritance on freedom of stroke means that it is easy to make 2.5 or even 2.6 litre version of the four cylinder, as Bill Blydenstein proved for many years, but to accommodate this longer stroke in production would have involved a different, separate block

casting with a higher top deck, but as the block retained the same cylinder bore centres much of the basic machining could have be carried out on the petrol engine transfer line. As we now know, only the 1599cc, 1759cc, 1975cc and 2279cc versions of the four cylinder petrol engine actually went in to production although the decision not to pursue the other versions was taken more on marketing and cost considerations than due to any engineering shortcoming of the hardware itself. In fact, the other versions proved to be very successful, satisfying Vauxhall’s incredibly stringent dyno-meter testing where the engine under test is cycled under full load for 500 hours between peak power & peak torque and subsequently run at 10 per cent faster than maximum engine speed.

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THE 1875cc SLANT FOUR DIESEL

The 1875cc diesel four cylinder above was completed for testing at the beginning of 1966 and gave 62bhp and 100lb-ft of torque which compares very well with the Opel CIH 2.0D which produced 60bhp and that was 10 years later.

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THE 3750cc V8 DIESEL WAS KILLED BEFORE ANY DYNAMIC TESTING HAD BEEN DONE

The 3750cc V8 diesel above was completed at the end of 1966 and featured a longer stroke with Lucas CAV injection into Ricardo style indirect combustion chambers but no ratings exist as the project was killed before any fuel settings were completed.

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THE IMPRESSIVE LOOKING 4 LITRE V8 PETROL ENGINE

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A CUTAWAY DRAWING OF THE STILLBORN 4 LITRE V8 PETROL ENGINE

The experimental 4 litre V8 petrol engine above was completed and first ran in September 1965. Considering that relatively little optimising of engine ignition and carburation settings were carried out it is impressive that the V8 petrol engine produced 195bhp and 245lb-ft of torque, both figures are gross, not net.

The early pre production slant four petrol engines were tested in FC Victors both at the Chaul End test facility and on the roads around Bedfordshire, none of the other experimental engines were tested in any cars or vans and never made it beyond the test rigs. Once the V8 and diesel projects were cancelled Vauxhall continued to work on projects that included a V8 as a proposed engine option but almost without exception these all used the Holden 4.2 litre V8. As far as diesels were concerned the CA and later CF Vans used Perkins engines until 1976 when the Opel 2.0D and 2.1D units were fitted instead to the CF range. Fuel injection was also planned, DTV had been using the engine with Tecalemit fuel injection from 1972 in their racing Firenza, Vauxhall planned an introduction in the mid 70's for the 2.3 VX4/90 and Firenza, not just for performance but also fuel economy and emissions, unfortunately it was shelved due to Lucas hiking its price and the impending merger of engineering & design with Opel, however initial testing rated the engine at 150bhp which might have made Opel feel a bit uncomfortable about their fuel injected CIH engine giving 115bhp! One special Firenza, Silver Bullet, and two VX4-90s and a Cavalier Coupe were fitted with these engines but only the Firenza survives today. In service the slant four was renowned from the start for being a high torque engine pulling from fairly low engine speeds especially the larger 2 and 2.3 litre versions, they were also known for being capable of very high mileages. Tuning was also common with both Blydenstein and Coburn Developments offering a multitude of DIY or dealer fitted Kits to increase power or economy. The smaller 1600 and 1800 versions were the smoothest, although none were particularly good in this respect. The problems though were numerous: Oil leaks from the rocker cover gasket dripping onto the exhaust manifold was very common but was usually because of ill fitment or over tightening of the securing screws which bent the cover and forced the gasket out of place. The performance of the 1600 even in the Viva HB was not much greater than the ohv “90” engine, in the Victor FD it was underpowered, and the 1800 suffered the same in the FE Victor. This lack of power was not matched by better fuel economy which was not good on any car fitted with any size of slant four. It wasn’t until extensive head and carburettor changes for 1976 these issues fully addressed. The engine also used to take forever to warm up as well, some owners removed the cooling fan without causing any overheating problems, after 1974 Vauxhall offered a 92 degree thermostat which helped. What didn’t help was the inlet manifold silting up and preventing water flow to the sender unit in the first place! Plugs were another issue, as with many Vauxhall engines they ran better with AC Delco but even with these they could need changing every 3,000 miles. The later versions used R42-5TS plugs with a large 40 tho plug gap which cured the problem. The last cars to use the 8 valve slant four was the HC Viva 1800 Automatic in 1979 but the CF continued to use it until 1984 even gaining electronic ignition for the last 3 years.

THE 16 VALVE DOHC SLANT FOUR:

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THE 2279cc 16v DOHC POWER UNIT WAS A "SNUG" FIT IN THE VAUXHALL CHEVETTE HS ENGINE BAY AS SHOWN ABOVE

When the Victor FD was first shown at the 1967 Earls Court Motor Show it was star attraction, the “coke bottle” design looked even better than the PC Cresta and HB Viva, and under the bonnet was the new slant 4 engine with revolutionary belt driven overhead camshaft. Part of Vauxhalls display was an engine on a stand with cut away sections showing how it all worked. Amongst the crowd eager to get a look at this advanced power unit was Lotus boss Colin Chapman. Nothing unusual in this, most company bosses and design and engineering staff would mingle with each other and discuss topics of interest (always trying not to give away any secret future plans of their own!) But with Chapman it was different he wanted to discuss his future plans and immediately set up a meeting with John Alden at Vauxhalls Design and Engineering Department, the reason was that the specification for Vauxhalls new engine were remarkably similar to the new engine that Lotus had just started working on, particularly the bore centres of the cylinders were exactly the same as those proposed by Lotus for their new all-alloy 900 series engine. A deal was negotiated for the supply of ten 1975cc blocks and four complete engines, using these as a template Chapman was certain that the initial development time for their engine could be halved. The result was the Vauxhall engine design became the basis for the Lotus 2.0 and 2.2 litre engines used in a wide variety of Lotus cars since. The main difference being the basic block was cast in aluminium alloy instead of iron which made it considerably lighter than the Vauxhall unit. The Lotus engine also used a light alloy cylinder head featuring double overhead camshafts and four valves per cylinder. The engines were so close in design that, with a few modifications, the Lotus alloy head can be fitted to the Vauxhall cast iron block, this interchangeability would cause Dealer Team Vauxhall problems with their rally Chevette in the late 1970s. At Vauxhall once the FD was launched the slant four engine found its way into the HB in both 1600 and 2000 GT versions and from 1969 in the Bedford CF Van. However, future model plans would require power, the FE Victor was already in development and was bigger and heavier than the FD. Late in 1968 two lines of development were started, a straight forward increase in capacity or by using a twin overhead camshaft but still using 8 valves, although Lotus were already using their 16v engine it was felt to be too complex an arrangement for the family car market Vauxhall aimed at. The other option to increase in capacity was tried in the following sizes: 1685cc 1759cc, 1889cc, 2105cc, 2279cc and 2390cc, the 8 valve twin cam head was fitted to the 2279cc and 2390cc engines for evaluation with both single and twin carburettor breathing. In April 1970 the choice was made for a straight increase in capacity to 1759 and 2279cc. One side issue from the research was the fitment of a lower lift camshaft in the 1599cc engine for the launch of the HC Viva and the last of the FD Victor 1600s to improve smoothness and fuel economy.  Following the experiments with the eight valve twin cam cylinder head work started on a 16v twin cam head, it was already acknowledged within the company that breathing especially at high revs was a problem with all slant four engines regardless of size. The first test engine, nicknamed “Old Number One”, was up and running by February 1973. The Lotus head was used as a rough template cum benchmark for the Vauxhall head but the camshaft carriers were angled upwards so that the covers were both horizontal as opposed to those on the Lotus engine which were equal about the cylinder centre line. Development continued for two more years and centred on fuel metering, carburation and running smoothness and idle most of which was done using one car – an FE VX4/90. The head could have been used in a high performance version of the VX4/90 but it would have required a large investment for a relatively low volume sales prospect. An unusual set of circumstances meant the new head was not wasted. Bob Price, always issuing memos (internally known as snowflakes as there were so many of them) on all sorts of subjects, one of these was sent to head of design Wayne Cherry and head of engineering Doug Bull. What he asked was simple – “How can we beat Ford at rallying?” The sport was becoming more and more popular and all the free publicity irritated Price. Cherry set about creating a suitably beefy looking mock up for a high performance Chevette while Doug Bull’s team began trying to shoehorn the 2.3 litre twin cam engine under the bonnet. By using a variety of Vauxhall and Opel parts mixed together it was done. In order to qualify it meant a production run for homologation would be required and so the Chevette HS was born, launched by mistake as a prize in a cigarette competition! The 16-valve engines used in the Chevette HS were all hand built and the heads were not mass produced but fabricated at the company’s engineering department workshop and so right from the start there were supply issues which held up car production but the DTV rally team that had been established around the car, and it’s ace driver - the late great Pentti Airikkala, continued to use the Lotus heads that they had initially experimented with. This led to the cars being prevented from starting the 1978 Rally of Portugal after protests from other teams. As a result all cars competing in international rallies were forced to use the Vauxhall head, and it then fell on Blydenstein Racing to get the same performance as the Lotus version, in the end they got to a point where it performed even better than the Lotus head.

ENGINE STATISTICS:

 

Production:            September 1967 to July 1983

 

Plant:                       Luton, CKD kits Australia, New Zealand, Antwerp, South Africa

 

Bore x Stroke        1599cc = 85.73mm X 69.24mm

                                1759cc = 85.73mm X 76.20mm

                                1975cc = 95.25mm X 69.24mm

                                2279cc = 97.40mm X 76.20mm

 

Power & Torque     1599cc = 72bhp (net) @ 5600rpm  83lb-ft @ 2200rpm  (Comp Ratio = 8.5:1)  1967 to 1972

                                1599cc = 83bhp (gross) @ 5800rpm  90lb-ft @ 3200rpm  (Comp Ratio = 8.5:1)  1967 to 1970

                                1599cc = 69.2bhp (net) @ 5100rpm  90lb-ft @ 2500rpm (Comp Ratio 8.5:1) 1970 to 1972 low lift cam fitted

                                1599cc = 80bhp (gross) @ 5500rpm  96lb-ft @ 2700rpm (Comp Ratio = 8.5:1) 1970 to 1972 low lift cam fitted

                                1759cc = 77bhp (net) @ 5100rpm  97lb-ft @ 3000rpm  (Comp Ratio = 8.5:1)  1972 to 1975 

                                1759cc = 90bhp (gross) @ 5200rpm  97lb-ft @ 3000rpm  (Comp Ratio = 8.5:1)  1972 to 1975 

                                1759cc = 88bhp (net) @ 5800rpm  99lb-ft @ 3500rpm  (Comp Ratio = 8.5:1) 1976 onwards
                                1975cc = 88bhp (net) @ 5500rpm  102lb-ft @ 3200rpm  (Comp Ratio = 8.5:1)  1967 to 1972 

                                1975cc = 104bhp (gross) @ 5800rpm  116lb-ft @ 3200rpm  (Comp Ratio = 8.5:) 1967 to 1972        

Canadian spec      1975cc = 77.5bhp (net) @ 5100rpm  100.5lb-ft @ 2800rpm  (Comp Ratio = 7.3:1)  1971 to 1972
Twin Carburettor   1975cc = 104bhp (net) @ 5600rpm  117lb-ft @ 3400rpm  (Comp Ratio = 8.5:1)  1968 to 1972

Twin Carburettor   1975cc = 112bhp (gross) @ 5400rpm  127lb-ft @ 3400rpm  (Comp Ratio = 8.5:1)  1968 to 1972

                                2279cc = 100bhp (net) @ 5200rpm  139lb-ft @ 3000rpm  (Comp Ratio = 8.5:1) 1972 to 1976                                                                          2279cc = 109bhp (net) @ 5000rpm  140lb-ft @ 3000rpm  (Comp Ratio = 8.5:1)  1976 to 1978                                                       Twin Carburettor   2279cc = 112bhp (net) @ 5400rpm  140lb-ft @ 3000rpm  (Comp Ratio = 8.5:1)  1972 to 1974
Twin Carburettor   2279cc = 122bhp (gross) @ 5600rpm  154lb-ft @ 3200rpm  (Comp Ratio = 8.5:1)  1972 to 1974                                               Twin Carburettor   2279cc = 116bhp (net) @ 5000rpm  145lb-ft @ 3000rpm  (Comp Ratio = 8.5:1)  1974 to 1978

Twin Carburettor   2279cc = 131bhp (net) @ 5500rpm  145.5lb-ft @ 3500rpm  (Comp Ratio = 9:2:1)  1974 to 1975 HPF                                        Twin Carb 16V        2279cc = 135bhp (net) @ 5500rpm  134lb-ft @ 4500rpm  (Comp Ratio = 8.5:1) 1978 to 1982 HS/HSR