Most CVH tuning is based on the 1600 engine although similar principles apply to the 1300 and 1400. The 1800 has a very poor flowing cylinder head designed for swirl and economy rather than power - also the camshaft is a roller follower design and quite different to the smaller engines - for these reasons the 1800 is not considered a suitable engine for tuning.

The 1600 CVH is one of my favourite engines for a number of reasons. It is simple in design and light in weight compared to earlier engines like the Pinto and Crossflow engine. The cylinder head is capable of very high flow figures when correctly modified and the power capability is good. The major weakness is is the valvetrain design - the camlobes are not well lubricated and the design requires high valve spring loads - these factors create a cam wear problem and even relatively low mileage standard engines will be found to have worn cam lobes. However, the cam is very easy to change and not expensive so I tend to treat it as a service item like brakes or tyres - a new cam and followers every couple of years and all is well again.

CYLINDER HEADS

The engine splits into 2 basic types - pre 1986 and post 1986 engines. (note: the EFi engines stayed as hemi design - only the carb engines went leanburn) The early engine has a hemispherical combustion chamber which is where the name "CVH" came from - "Compound Valve angle Hemispherical chamber". This head flows very well when the ports are reshaped properly - higher flow for example than a big valve Pinto engine. Sadly very few engine tuners seem to have done any flowbench development to find the right port shapes because I see modified heads all the time which flow little more than standard. Some years ago I was brought a so called "full race" engine from a well known Ford tuning firm on which the "modified" head actually flowed worse than standard except for a very minor improvement at high valve lift. That engine made another 17 bhp with just the head reworked properly.

The post 1986 leanburn engine has "heart" shaped combustion chambers rather like those of a Mini engine and different pistons. Also the oil pump design was changed slightly and the carb is smaller but the engines are otherwise the same. The lean burn head suffers from some valve shrouding by the chamber walls and so flow is not so high as the early head design. The differences are not major though and a tuned road engine will produce perhaps 5 bhp less than a similar hemi engine. The lean burn head requires lots of metal removal in the chamber as well as the ports to obtain good flow and so takes a lot longer to modify than the hemi head. Given that all this extra work costs more money and ends up producing less power too, I generally convert late engines to hemi design if cylinder heads are available and if high power is critical.

There are several different head castings which Ford used over the years and getting the best out of this engine requires knowledge of which type of castings flow best and have the most potential for improvement. To the uneducated eye they all look pretty similar. For mild road tuned engines the choice is not critical but for ultimate engines and especially big valve heads the right casting numbers need to be used. The CVH responds very well to big inlet valves. I have my own valves made and offer 43.5mm and 45mm inlets in addition to the standard 42mm heads. Other so called "big valves" available are only 42.6 or 43mm and hardly worth fitting which is why I designed my own. However, very few heads can use the 45mm valves because you'll break through into a waterway trying to open the ports up enough. The best heads to use for 45mm valves are the XR2i ones from 1989 onwards, casting number 89SM6090 but you can't use those with DCOEs without some welding. There is also a rare variant of the pre 1986 casting (81SM6090) that has thick enough port walls to allow 45mm valves to be used but I see very few of those nowadays. You can tell them by the cross-hatch pattern cast on the outside of the head.

The exhaust valves are actually far too big as standard. 37mm is a huge exhaust valve for a 1600cc engine. The 2 litre Pinto has 36mm ones, Peugeot 1.9 Gti are 34.5mm, Golf Gti even smaller. Under no circumstances fit larger exhaust valves and any tuning firm that does this can be safely avoided as they have no clue how to modify this engine properly.

There are certain things that absolutely must be done to portshapes to get the CVH head to flow to its full potential. The area around the valve guide where the port bends is critical and this must be straightened out and shaped to blend nicely into the valve throat. You MUST remove the valve guides to get at this area so any head which just has a bit of polishing and no real constructive port work will not show much of an improvement. That means most off the shelf heads you are likely to buy. Every head I do has the guides removed first so that the ports can be modified to the correct shape for high flow.

IDENTIFYING ENGINE TYPE

The primary identification without taking the engine apart is to go by the casting number on the inlet port side of the cylinder head. The first two digits indicate the design year of the head.

81SM6090 - pre 1986 hemi head (1600 Escort, Fiesta XR2, Bosch K XR3i etc)
There are two variants of this head. The standard casting and the rare cross-hatch casting. The standard casting has a plain flat finish to the external sides of the head. It's a good head for standard or 43.5mm valves. The cross-hatch casting has a ribbed cross-hatch pattern on the external sides and has thicker port walls and a better port shape. Only the cross-hatch casting can be used for 45mm valves.

86SM6090 - Lean burn head on post 1986 carb engined models.

88SM6090 - Generally these are hemi heads on the few carb engines that didn't go to leanburn in 1986 (Some Escorts/Orions I think) but see below. Essentially similar to the 81SM head but fairly rare to find one. I suspect the only intended difference is they'll have seat inserts fitted designed specifically for unleaded fuel. However, they also tend to have very bad port shapes and can't be modified for good flow or you'll break into a waterway. Best avoided even for ported standard valve work and absolutely no good for big valves.

88SM6090 - Just to confuse things some of the 88SM heads are leanburn although I've only come across a couple in 15 years.

89SM6090 - The EFi hemi head from Bosch L Fiesta XR2i's and XR3i's. Also has the injector cutouts in the inlet ports and therefore won't take a DCOE manifold without welding or other tinkering. Good head for big valves though as the port walls are very thick and the port shapes are excellent for flow.

UNLEADED FUEL

All UK cars sold after 1988 had to run unleaded fuel as standard so 88SM and later heads had seat inserts specifically designed for this. However the inserts in the earlier heads, as with pretty much any aluminium cylinder headed engine, have proven quite happy on unleaded for road use despite plenty of tuners offering to lighten your wallet for "unleaded" conversions. Given that I'm sure they all know that I wonder if they do even change the inserts or whether they just clean up the head and take your money. I've seen just one race engine with an early head that suffered exhaust seat insert wear so for race use it might be adviseable to change them on pre 1988 heads but then I've also seen many other race engines with pre 1988 heads that had no problem at all.

CAMSHAFTS

There are plenty of cams available for this engine from Piper and Kent etc. Some of them are ok with a reasonable improvement in high rpm power in exchange for a fair loss of low rpm power - others are awful and best avoided. I designed, and used to sell, two road cams for the CVH that went somewhat further than the off the shelf cams available at the time but problems obtaining high enough quality blanks to grind them on means that I no longer supply them unless I have a decent blank in stock. Two cams worth looking at from Kent are the CVH22 and the CVH33. The CVH22 will run with the standard valve springs and is worth about 6 or 7 bhp with decent low rpm tractability. The CVH33 is about as far as you can go with a road cam and still retain any sort of driveability. It loses out under 2,000 rpm but gives about 10 to 12 bhp at the top end. Lift is too high for the standard springs. Copyright David Baker and Puma Race Engines

CAM WEAR PROBLEMS

I alluded briefly to the CVH cam wear problem in the introduction. As this crops up so often on newsgroups and emails I'll expand on the matter. The CVH cam is lubricated by the oil that drips through little brass bushes next to the rockers. Even this limited supply can disappear if the bushes clog with carbon due to infrequent oil changes and cheap oil. Also the valve spring is extremely stiff compared to other engine designs. It generates a load at full lift of 220 lbs compared say to 125 lbs for a Pinto or Mini engine, 150 lbs for an MGB. This high spring load is necessary to control the heavy rocker and lifter and still only allows about 6,700 rpm before valve float starts. To compound the matter, Ford didn't use the best available material for the camshafts. "Chill cast" camshafts last several times longer than the induction hardened material used in the CVH.

Cam wear is therefore a fact of life with the CVH. Most other types of engine show little or no cam wear in normal use and if wear does start then it tends to accelerate exponentially leading to rapid failure. Standard CVH cams wear steadily from the moment they are fitted. I've never stripped a medium mileage road CVH engine that didn't have considerable wear on the lobes and lifters. The problem is worst on cylinder 4 next to the fuel pump lobe. This is nothing to do with the urban myth about cylinder 4 being furthest from the oil pump. Whoever started that one wasn't the world's deepest thinker. The oil supply runs up through the block between cylinders 2 & 3 so in fact cylinder 1 is as far from the pump as cylinder 4 despite being right above it. In fact there is a design fault in the engine which means that the cam lobes on number 4 are not properly positioned relative to the lifter bores.

Cam wear starts to take place about half way up the lobe. It then leads to dishing of the lifter base and loss of material over the cam nose. As the lifters dish, a sharp lip is created round the base of the lifter which means they often won't withdraw through the lifter bore. If this occurs then under no circumstances try to graunch the old lifters out with a pair of pliers. You'll score the lifter bores and ruin the oil pressure to the lifters. Raise the lifters until they are clear of the cam lobes, remove the cam and then push the lifters into the head and get them out through the distributor housing bore. Check every lifter bore for wear. On neglected engines the bores can wear and this means the head is scrap. Take a lifter and turn it upside down so you aren't inserting the lip into the bore - better still use a new lifter if you have one. It should just slide into the bore with no appreciable rock.

There is NO, I repeat NO point in fitting new lifters to an old cam in the hope of fixing a noisy engine. The new lifters will be reduced to scrap by the worn cam lobes within minutes of starting the engine. Replace everything, clean the brass lubrication bushes and if the head is really badly clagged up (which they tend to be) then remove the head and have it chemically cleaned to remove all carbon deposits from the oilways. Then fit and run the new cam and lifters in properly - use plenty of cam lube on the lobes and lifter bases and don't let the engine idle for the first 15/20 minutes - keep the revs at around 2000 which gives the cam a chance to bed in and work harden. Change the oil and filter too (flush the engine out as well if you want to do the job properly) - all that material that wore off the old cam lobes is down in the sump gradually wrecking the crank bearings and oil pump.

Fix a worn cam problem properly and you'll get as good a life out of the new one as you did from the original. Get it wrong, leave the oilways blocked, fail to use cam lube or run in properly and you'll be doing the job for a second time within weeks.

CRANKS AND BLOCKS

A popular conversion for the 1600 is to take it to 1905cc with cranks and rods from the 1800 CVH engine and special pistons. This is quite a complex conversion though and not just a matter of dropping the standard 1.8 crank and rods in the 1.6 block. This spec is commonly sold by other tuners with standard head and cam and quoted as being a 130 bhp engine. In reality it only develops about 105 to 110 bhp. Extra capacity on its own does relatively little for power until cylinder head flow and cam lift have been improved in proportion. That's an expensive 10 to 15 horsepower gain considering those sort of engines are priced at about £2,000. Peak power comes in very low at 5,000 rpm or so and although the mid range torque is nice, the lack of rev range makes it pretty dull to drive. You can get the same power for much less money with head and cam work than you can with capacity increases. Look at the chart below and you can see that a mild road cam and properly modified head will achieve more power on a std 1600 engine than the entire 1905cc engine develops at over three times the cost.

To make the big engines go well you must use high flowing heads, good cams and plenty of carburation. A properly built 1905cc really ought to be making about 150 genuine bhp if it is done right and in a Fiesta size car that's pretty damn quick.

I offer a standard 1600, a 1700 and the 1905 as well as specials up to 2.1 litres for people who really want to prove a point although the 2 litre plus engines cost a fortune to build so don't get too excited unless you have about £4,000 burning a hole in your pocket.  Again, there are several different versions of the block as Ford constantly changed the design over the years. Picking the right type is essential.

The engine is so simple that it's pretty hard to assemble it wrong but despite this the one thing that few people get right is fitting the oil pump. DO NOT try and force this to line up with the sump flange. The oil pump must be central on the crank nose and NOT forced to one side. If you take up all the clearance in the pump gears by trying to align the pump flange with the sump flange then the gears will get smashed by crank vibration and pushed through the side of the pump. Fit the pump loosely and move it from side to side and up and down until you get a feel for the amount of free play between the pump and crank. Then position it as central as you can and nip the bolts up. Any error relative to the sump flange will be sealed fine if you use a bit of silicone on the sump gasket. 9 out of 10 engines that fail soon after rebuild are because the pump breaks due to incorrect fitting. Ford changed the design in 1986 to try and make it a bit more idiot proof but in my experience there is nothing capable of doing quite as much damage to an engine as a really determined idiot.

POWER OUTPUTS

The standard hemi engine is rated at 96 PS (94 BHP) although that is pretty optimistic I find. A normal standard engine in good condition puts out about 75 bhp at the wheels - 90 to 92 ish at the flywheel. The leanburn engine with its smaller carb and worse head makes a couple of bhp less - mainly because of the head I feel because the TLD carb seems to work quite well on tuned engines despite its small size. Copyright David Baker and Puma Race Engines

With a properly modified standard valve size head and Stage 1 cam, a 1600 will show about 115 flywheel bhp on the standard carb - that's about 98 bhp at the wheels. Add a pair of Weber DCOEs and the Stage 2 cam and 130 flywheel - 110 wheel bhp - is easily possible. In 1700 cc form I have an engine to that spec with a solid 140 bhp plus doing the rounds of the dragstrips in Aberdeen which shows a clean pair of heels to 16 valve Golfs and Vauxhalls and the like. Add a big valve head to any of the above specs and you get around 10 extra bhp but valve cutouts can be needed in the pistons so this is best done together. When I build a fast road engine I put the necessary cutouts in anyway in case a big valve head is added at a later date. When power levels get serious, a decent exhaust manifold and system can be worth 5 bhp or so - a tad more on big engines. Beware of systems with huge pipe diameters though - they are not necessary and hurt power. The standard air filter casing is also restrictive on the CVH engines and a K&N or similar is worth a few bhp. Sometimes they can cause carb icing in the winter though due to the lack of warm air pick up in which case fit the standard one back again until the weather warms up.

Ultimate power from the bigger engines with big valve heads and throttle body fuel injection is 170 bhp plus - enough to seriously embarrass Cosworths. Here's a chart to make it all a bit easier to read. This is based on the hemi engine so deduct 5 bhp for a lean burn in the same state of tune.

Transmission losses are about 15% of the flywheel figure so the 90 at the wheels you just saw on the rollers is NOT 150 bhp flywheel whatever the nice man in the white coat told you. The power figures I show are achievable and repeatable but not easy to get - they require state of the art head work and good cam design and you won't get them by buying a mish mash of bits from different companies and bolting it all together. What you will often get though if you go to a rolling road is a nonsense flywheel figure based on a huge estimated transmission loss to make the low wheel figure look better. Always ask for the wheel figure when you get your car set up and then divide by 0.85 to get an approximation of the flywheel figure. Don't take any notice of so called flywheel bhp printouts produced by the rolling road computer - they usually aren't correct. For more on transmission losses read the power and torque articles on the main menu page.
 

INJECTION ENGINES

There are two main types of injection engine - the early K jetronic system in the original XR3i is a mechanical injection system where the injectors flow all the time. From 1989 on, the XR2i and injection Escorts have a derivative of the Bosch L EFi injection. This has electronic injectors which are pulsed to flow fuel only when the inlet valves are open.

Bosch K type engines

The base engine is exactly the same as the carburettor engine - same head, cam, compression ratio - everything. The claimed 9 bhp increase to 105 PS (103 BHP) comes entirely from the injection system therefore and in my experience is well optimistic. A good XR3i shows about 80 at the wheels, 5 up on the carb engine and therefore in the high 90s at the flywheel. Ford had a serious marketing problem with the XR3i which they insisted on being the performance car in the range despite the Fiesta being lighter and a better match for the other hot hatches like the Golf and Astra. Even with the injection system fitted, the XR3i was slower than the XR2 and Ford fitted a much lower geared diff to the XR3i to try and give it a bit more sparkle. It took them nearly ten years to add injection and finally a turbo to the Fiesta - just in time in fact to miss the entire period of the hot hatch craze which was starting to die by the late 1980s/early 1990s. Nice one Ford ! - your marketing boys obviously have an uncanny feel for the trends in motoring fashion - NOT.

The injection system won't give as much power as a pair of sidedrafts but otherwise tuning recommendations stay about the same as for the carburetted cars. Deduct about 5 to 10 bhp from the DCOE power figures so a 1600 with properly ported standard valve head and 274 cam will show about 120 to 125 flywheel bhp.
Bosch L Type EFi Engines

To boost power further, Ford did some head and cam work on these engines and the compression ratio is a little higher too. The valve shape is better for flow and the head casting has "cutouts" in the ends of the inlet ports for the injectors to fit into. The head flows considerably better than the non EFi casting as standard but has exactly the same flow potential when fully modified - think of it as Ford having already done some of the porting work for you. In all other respects the head is the same as an early hemi head. The cam has more lift and duration than the standard XR cams and therefore you will see less of a power gain if a performance cam is used. The EFi cam is already worth about 3 to 4 bhp more than the standard engine cam.

Claimed power was 110 PS (108 BHP) - only 5 up on the claims for the XR3i - however this 108 bhp is much more realistic than the 103 bhp ever was in the earlier engine. The head and cam work already done by Ford are worth about 8 bhp over the same items in a Bosch K engine, so whereas a good early Bosch K XR3i will only show high 90s bhp flywheel (80ish wheel bhp) a good XR2i will show closer to 90 at the wheels indicating perhaps 106 bhp flywheel. Power potential is about the same as the earlier injection engine - a genuine 120 bhp or a tad more is a decent target with a good head and 274 cam - add another 10 bhp for a big valve head. Best not to go too wild on the cam duration on the EFi or the airflow sensor can get confused. Of course you can always fit DCOEs or throttle bodies in place of the standard injection system and refit it when you sell the car - then you are back to the power targets in the chart above. A standard DCOE manifold isn't a straight swap though as it won't seal over the injector cutouts in the inlet ports. Can be solved by welding extra material to the manifold if you want to go that route.

The EFi injection system is very easy to set up when engine modifications have been made because there is an adjustable fuel pressure regulator already built into the system. Prise off the cap and underneath is a 4mm allen key screw. Wind this in to raise the fuel pressure. One full turn increases the pressure by about 7 psi and is about as much as most engine mods need to get the fueling right at the top end. Mind you it won't let you alter just the low rpm fueling - it raises it everywhere obviously so more complex mods are needed to get the mixture perfect everywhere in the rpm range if there is a specific weak or rich spot. It was good enough for my own car though given the cost of a system which would enable perfect fueling everywhere. With a fully modified standard valve head I find that not only mid range and high rpm power increase but also low speed tractability improves. Fit the head which is a mornings job and tweak the fuel pressure by between half and one full turn. No need for rolling roads or any other set up expense. What could be easier. You can adjust the screw until the engine feels strongest and wind it back in whenever you like to regain a tad more fuel economy. I pulled 51 mpg out of my own 45mm valve head XR2i during the fuel crisis in 2000.

If you want an ultimate engine then the route to go is mappable ignition and injection with throttle bodies. In this case either of the injected engines is a perfect base because they already have the high pressure fuel pump and wiring to make such a conversion easier. Capacity increases are also well worth considering if you want good power but without losing low end tractability.

Whether you start off with a base model Escort engine rated at 88 bhp or an injected XR2i engine rated at 108 bhp, all these engines have the same power potential in the same state of tune. Just because your starting point is higher doesn't mean you will end up with more bhp at the end. It just means that Ford has already realized some of the power potential inherent in the engine design for you and that power increase per £ is going to be less for the same tuning work. If you intend to build an all out engine with twin DCOEs or throttle bodies then you might as well start with a base model engine as waste money on higher spec engines when the parts will still get changed anyway.

PRICES
 

Pre 86 hemi head - ported standard valve with new guides, shortened and reshaped - £600. This head will give 140 bhp (117 to 120 wheel bhp) with DCOEs and a CVH33 cam. This is effectively a race spec ported head in anyone else's book.

Pre 86 hemi head - 43.5mm inlet valve which are the largest that can be fitted on the standard seat inserts - £800. This head is worth an extra 8 or so bhp over the std valve head. Ideally it should be done on selected castings and we can advise as necessary before work commences.

Pre 86 hemi head - 45mm inlet valves on big seat inserts - the ultimate CVH road or race head - £1000. This needs to be done on selected cross-hatch 81SM castings or the EFi injection head. Standard castings will break through into a waterway before the ports are enlarged enough to make this valve size really flow. Best suited to bigger capacity engines because this head flows so much air that a 1600 bottom end will need to rev beyond 7,500 to make use of the flow and this is pushing the limit for what the rods and pistons will stand. With forged pistons and a steel bottom end this head can of course be used to advantage on race engines. Most of these I've done have been for 2 litre ZVH turbo engines such as Sean Richardson's which made 428 bhp on 28 psi of boost.

Double valve spring system £130 - Trying to run double springs such as those that come with most cam kits on the standard caps and spring bases doesn't work properly. The springs aren't located correctly and usually either the inner or outer spring goes coilbound long before the other one. Consequently the correct preload isn't generated and the engine won't rev as high as it ought to. In fact it isn't unusual for the double springs available from the well known cam companies to valve bounce at lower rpm than the standard springs - 6,500 rpm has been reported to us by several customers.

I must also add a warning about the so called "uprated" single valve springs sold by the cam companies with their high lift cams. These springs, far from being uprated, are actually weaker than the standard Ford springs. To enable the fitment of higher lift cams without the spring going coil bound these non standard single springs are just made from thinner and hence weaker wire which allows them to compress to a shorter length. This gives the clearance the high lift cam needs but means valve bounce long before the cam wants to stop revving. It beggars belief that such useless equipment is still being sold after so many years but that's the tuning industry in this country for you. The only proper solution for high rpm engines is correctly designed double springs like our own.

Our own system is designed to solve all these problems and enable rpms close to 7,500 on the hydraulic lifters and higher still on solid lifters. It is designed for cams that lift more than 450 thou which is about the limit for the standard valve springs but can be used with any cam, even the standard one, if desired. It will cope with lifts up to 550 thou which is higher than any cam currently available. It includes spring caps machined to locate the inner spring properly and requires your old caps on exchange. I can supply caps outright for an extra £15 if I have any in stock. It also includes special high quality stem seals which won't go hard like the standard Ford ones and thick spring seat washers machined from steel bar which properly locate the inner and outer spring and sets the correct preload for high rpm use. We strongly recommend that even if you buy your cam from someone else, just get the cam rather than the cam kit and use our spring system with it. It'll be cheaper in the long run than buying a complete cam kit, finding it valve bounces before the engine wants to stop revving and then have to buy proper springs again to solve the problem.

Fitting Instructions For Double Spring System

Many CVH heads have a burr on the inside edge of the aluminium valve spring seat around the valve guide. Remove this with the end of a small file or scraper until the entire seat surface is flat. Fit the 4mm thick seat washer with the recessed side uppermost. This recess locates the inner spring. Then fit the stem seals. Lubricate inside with oil and tap gently into place on the valve guide with a small socket or length of tube. Fit the valve and spring in the normal way, making sure the inner spring locates into the washer recess.
 

CVH Cooling

VALVE SEAT FAILURE

The most common problem with the CVH is the tendency to drop a valve seat,[2] which most often happens in the 2000-2004 Ford Focus with the 2.0L CVH/SPI SOHC engine. This problem is also seen in 1991-2002 Ford Escorts. These engines usually drop a valve seat with no warning, even if the engine has been well maintained. In most cases, a seat drops on the number 4 cylinder, with the next most common being the number 2 cylinder. With the factory valve seats, the typical life of the 2.0L SPI in a Focus is about 100-120k miles,[3] but it can happen as early as 70k miles. When the valve seat drops out of the cylinder head, it falls into the cylinder and damages the piston and cylinder head. In some cases, the valve seat is drawn from its cylinder through the intake manifold into another cylinder until it is obliterated. A valve seat dropping into the cylinder can scar the cylinder wall and bend the piston connecting rods. When repairing an SPI with a dropped valve seat, it is very important to remove the intake manifold and clean it thoroughly before bolting it up to a new cylinder head. If not cleaned, trapped particles in the manifold from the dropped valve seat will enter the repaired engine and scar the cylinder walls and sometimes ruin the new cylinder head. The best solution for avoiding the dropped valve seat problem is to purchase and install a new cylinder head that has had the valve seat problem fixed.

Valve Stem Seals

Valve stem seals often harden and start to pass excessive oil, causing a smoky exhaust after the engine has been allowed to over-run. Fortunately workshop tools are available that allow the CVH valve spring and collet to be removed, and the seal replaced, without removal of the cylinder head.