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Tuning guides for Kent / X-Flow - Have you used them as a bible?

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2015/05/09 16:45:25 (permalink)

Tuning guides for Kent / X-Flow - Have you used them as a bible?

I was wondering if anybody used any of the following guides to build an engine, if so what parts did you use, do you regret any of your decisions?
The information below is taken directly from Burton Power web site-
This engine was introduced in the Ford Mk2 Cortina and differs from the earlier units by having the carb on the left and the exhaust on the right - hence, ‘crossflow.’
They also varied from Pre-X/Flows in that the combustion chamber was shifted from the head to the bowl of the piston and were know as BIP engines (Bowl In Piston). Early heads also feature a small combustion chamber in the head too.
Early blocks bore the casting marks 681F and capacities you’ll find are, 940, 1098, 1298 and 1599. You’ll find a X/Flow fitted to Mk1/2 Escorts, Mk2/3 Cortinas, Mk1/2 Capris plus late Transits. Most cars came with a single choke Ford IV carb although the 1.3 and 1.6 GT models had a 32/36 DGV Weber twin choke.
1970 saw the big change to the thicker-walled 711M block with square mains caps, large diameter followers, wider cam lobes and modified crank seal. Also, the head was now completely flat.
There are two main capacities of 711M, determined by block height - the 1600 is 7/16" taller and you can see the difference between it and the 1300 by the space between the water pump and head. Also, the 1300 has 711M 6015 AA cast in the side whereas the 1600 ends in BA.
The engine was also fitted to 1.3 and 1.6 Mk1 Fiestas in the 80’s with a 771M casting. These feature no side engine mounts plus a shortened water pump and timing chain/crank area.
The final versions, OHV, HCS and Endura are similar but shorter versions and share very few if any inter-changeable parts and reverted back to the original pre-X/flow design of a three bearing crank.
Kents are quite easy to tune to GT spec, which usually means the biggest capacity block, slightly bigger valves (usually taken care of with a performance head), GT cam/A1, free flow exhaust and twin choke Weber - you should see around 80-90bhp. Switch to a Kent BCF2 or a 224 and you’ll be approaching 110bhp. For all builds we would recommend ARP rod bolts and replacement of the front pulley for a one piece steel item. The valve train should be strengthened with steel posts, spacers and rocker shaft to cope with the additional stresses caused by high lift cams, HD valve springs and higher revs. A double timing chain kit should also be fitted for the same reasons. Performance heads are available in both iron and brand new aluminium and all can be ordered with unleaded seats.
You can use the old Cosworth A-series cam profiles too, which are long duration and lower lift. However the current Kent Cams, high lift and short duration type are friendlier on emissions with less lobe overlap resulting in reduced un-burnt fuel down the exhaust.
Add a stage 2 head and Kent 224 and you’ll be pushing 115bhp although the favourite X/Flow cam is the 234 for 118-120bhp. You should get this with a re-jetted twin choke although twin 40 DCOE Webers would be better. This is an all round great cam and engine spec for the road.
A 244 cam and stage 3 head results in 135-145bhp, although, these figures are best achieved with a recommended maximum 83.5mm bore and forged Accralite pistons, giving 1700cc. There is a cheaper option in that the compression can be raised using modified 1300 pistons in the 1600 engine, giving a ratio of around 10.3:1. Capacity is easily increased with cast pistons available up to +0.090" oversize which will give 1696cc.
40 DCOEs tend to be on their maximum choke sizes at this stage so many switch to 45s. However this does result in lower gas speed and less low down torque, which is important on the road.
All side draughts need a side exit distributor cap (available for Lucas and Bosch distributors) to clear the inlet manifold and for convenience it’s best to fit an electronic ignition kit such as an Aldon Ignitor or Lumenition. For a complete ignition solution, our constant energy, non-vacuum modified Bosch distributor and coil kit is ideal for most modified engines.
This is about as far as you want to go on the road since you’ll be stretching the 7500-8000rpm limit of the crank. After this and you’ll ideally need steel components, which we have a superb range including cranks, rods, flywheels and forged pistons. To complement these we also have full-race spec heads to take the Kent as far as possible on the race track - currently that’s about 185bhp+."

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    Re: Tuning guides for Kent / X-Flow - Have you used them as a bible? 2015/05/09 16:50:28 (permalink)
    Has anybody used this tuning guide? -
    Rebuilding and Tuning Ford's Kent Crossflow Engine by Peter Wallage, Valerie Wallage.
    I have a copy of it.
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    Re: Tuning guides for Kent / X-Flow - Have you used them as a bible? 2015/05/09 16:57:45 (permalink)
    Just some info / specs on Kent Cams for Kent X-Flow- Do you regret your choice?


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    Re: Tuning guides for Kent / X-Flow - Have you used them as a bible? 2015/05/09 19:14:52 (permalink)
    RCMA X-Flow Tuning Guide - Cant remember where I got it? It was a PDF that I was able to copy and paste into a word document, then edit to neaten it up - all but the pretty pictures :)
    (The tables wont copy from word over to the site so if anybody wants a PDF or word copy of it, let me know and I will email you.) I am at gmail dot com.
    Any advise followed / regrets?
    Our new tech series looks at the engines that have shaped a generation of classic Fords.
    This month we start with one of our favorites, the Kent Crossflow.
    The Crossflow is an awesome engine. Not necessarily in terms of power but merely from the point of view of its history. One of Ford's bread-and-butter power plants from the '60s through to the '80s and it's still going strong.
    It's been raced in endless forms and right now there are still new versions being developed. The Crossflow laid the foundations for the infamous Cosworth-BD series, plus there are even brand-new aluminum blocks and heads being produced to give crazy capacity and power. In fact, in terms of its shear doggedness, it's been likened to the infamous small-block Chevy for the simple fact that it just won't die.
    Named because the bloke who designed it, Alan Worters, lived in Kent, the good old Crossflow, as it's been commonly named, is a derivative of an older engine also called Kent. The difference is in the head and block, with the older unit known as the Pre-Crossflow. This earlier version of the 997cc, first saw service in the 107E Prefect and 105E Anglia in October 1959 and went on to be produced in 1198 (Anglia and Cortina), 1340 (Ford Classic) and 1498cc (Cortina) forms.
    The big break came in September 1967 with the Mk2 Cortina when the engine was redesigned to carry a crossflow head. These early Crossflows were available in 1297 and 1598cc form, known as 1300 and 1600 respectively. The latter carried the casting number of 691M. As we'll see, the head was different to later designs since it's slightly chambered later ones are flat. The big difference over the Pre-Crossflow, was obviously the crossflow configuration — where the inlet ports are on one side and the exhaust ports on the other. But, in addition, the type of combustion chamber design's important too. The Crossflow has what's called the Heron principal, which means that the combustion chamber is in the piston rather than the head. In fact the new engine was marketed in the Mk2 Cortina by the name — Bowl-ln-Piston.
    The big crossflow change came in mid-1970 with the Escort Mexico. Designated the 711M since that's what's cast in the side.
    These blocks and heads were different to the former version. For a start, the blocks strengthened with a stiffer crankcase and stronger main bearing caps — they're now square shouldered as opposed to the earlier round type. There are other minor differences too, for example, they have a more modern screw-in oil filter type of pump rather than the canister and element version fitted to the Mk2 Cortina.
    The other main difference is in the head face, which is now flat, while the block carries the corresponding pistons to go with it. These later engines are the ones most suited to high-power tuning.
    You will find 711s in both 1300 and 1600ccform in virtually every Ford car from then on. Look under the bonnet of both, Mk1 and Mk2 Escorts, Mk2 Capris, Mk3 Cortina’s, even very late Transits and you'll find a 711 M of some sort. The engine was slowly phased out of the various models, some in favor of the Pinto or the CVH in the case of the Mk3 Escort.
    However, the engine still lives on, although in a slightly different form. Now dubbed the Endura, a version still powers the current KA, and previously the Fiesta in 850 and 1100cc Valencia versions. These are quite dissimilar to the regular Kent in that they have no side engine-mounting bosses, since they are meant for front-wheel drive use only. Very late engines don't have a distributor either, as they are fired by crank trigger.
    This significant change happened with the introduction of the Mk1 XR2, which also uses a Kent Crossflow. This engine with casting marks 771 M, is basically similar except that it's shortened to fit between the chassis rails of a Fiesta in front wheel- drive configuration. The crank is therefore shorter, so too is the timing cover and water pump. We'll see though, that the Fiesta Crossflow can be tuned the same as any other.

    Tech Specs

    To get right down to basics, the Crossflow’s an all cast iron lump of overhead-valve design with two valves per cylinder, operated via pushrods and rocker gear from a cam, driven at half crank speed, mounted in the right hand side of the block. This in turn is driven by the cast crank and by a single thickness timing chain.
    The engine has normal type cast connecting rods; with anodized aluminum alloy pistons and solid skirts. Ignition is provided by traditional coil and distributor fitted with points. Induction is via carburetor with two basic types being used – single downdraught and twin choke on the GT/Sport models.
    There are of course varying types of crossflow depending on the vehicle’s intended use. Therefore there are technical variations within the engine, basically taking the form of low and high compression. While GT versions typically house different carbs, cams and exhausts as well. All crossflows carry the same bore size of 80.978mm (3.1881 inches) with the different capacity being taken up with stroke.
    The stroke differences are-
    1100cc - 53.29mm
    1300cc - 62.99mm
    1600cc – 77.62mm
    It’s also possible to tell the difference between 1300 and 1600 externally, by the casting marks. The 711M series has 711M-6015-A-A for the 1100/1300 and –B-A for the 1600 The 691’s have a very similar code also ending in the BA and AA configuration. The smaller capacity blocks have physically less material between the water pump and deck face of around 25mm – due to the shorter stroke.
    There are also variations in compression ratio (CR), not only between the differences in capacity but also within the same capacity. Therefore you get a high and low compression 1600 – as in the late Transit. However, these are often easily spotted by the HC sticker on the top of the rocker cover. MK2 Escorts can tell you what CR they have by the VIN plate under the ‘Motor’ section.
    Engine Fitting Pre-Crossflow to Crossflow
    Nearly every classic Ford was fitted with a Crossflow — except of course the big ones like Granadas and Zephyrs. The only real time retro fitting a Crossflow's a consideration, is to replace the engine in a car that was originally fitted with a pre-crossflow, in which case, a Crossflow swap is a doddle. All you need is the sump from a Mk2 Cortina, ideally 1600.
    This sump is a front bowl-type, rather than the Escort's, which is rear — this is necessary to clear the steering rack. All you need then is the corresponding pick up pipe and dipstick tube and you're sorted. We'd also use Escort engine mount rubbers as the standard Cortina/Anglia ones don't last long.
    The last consideration is gearbox, but this is only a drama if you intend swapping to a five-speed and want to retain a hydraulic clutch. There are ones you can use — Mk2 I Cortina or, use an RS2000 bell housing plus an eccentric hydraulic thrust bearing kit from Retro Ford.

    Mk2 VIN Guide

    Engine code 
    Compression Ratio
    (twin choke) 9.0:1
    (twin choke) 9.0:1
    (twin choke) 9.0:1
    Cortina Mk2 1300 HC
    58 at 5000
    71.5 at 2500
    Cortina MK1 11300 LC
    53.5 at 5000
    68.0 at 2500
    Cortina Mk2 1600HC
    71 at 5000
    83.5 at 2500
    Cortina Mk2 1600 LC
    69.5 at 5000
    80.0 at 2700
    Cortina Mk2 1600 GT
    88 at 5400
    91.5 at 2500
    Escort Mk1 1100
    53 at 5500
    62 at 3000
    Escort Mk2 300 Super
    63 at 5000
    75.5 at 2500
    Escort Mk1 1300 GT
    75 at 5400
    91 at 3800
    Escort Mkl2 1100
    48 at 5000
    54 at 3000
    Escort Mk1 1300
    57 at 5500
    67 at 3000
    Escort Mk2 1300 Sport/Ghia
    70 at 5500
    68 at 4000
    Escort Mk2 1600 Sport/Ghia
    84 at 5500
    92 at 2500
    Capri Mk1 1300
    52 at 5000
    66 at 2500
    Capri Mk1 1300 (post 1970)
    57 at 5700
    66 at 3000
    Capri Mk1 1300 GT
    64 at 6000
    64.5 at 4000
    Capri Mk1 1300 GT (post 1970)
    72 at 5500
    65 at 2500
    Capri Mk1 600 GT
    82 at 5400
    92 at 3600
    Capri Mk1 1600 GT (post 1970)
    86 at 5700
    92 at 3600
    Capri Mkl2 1300
    57 at 5500
    67 at 3000
    Cortina Mk3 1300
    57 at 5500
    67 at 3000
    Cortina Mk3 1600
    68 at 5200
    85 at 2600
    Fiesta XR2
    84 at 5500
    91 at 2800


    Because of the increase in strengthening in the 711 series' engines, these are the ones that most tuners will favour and therefore the ones that we'll concentrate on. On the same note, it's also more usual to concentrate on the bigger capacity engine. Simply because you can spend a fortune on a smaller motor, only to achieve the power that a weekend engine swap would give. That isn't to say that the principals we'll discuss don't apply to say, a 1300 Crossflow, though.

    Induction and Ignition

    You can actually do quite a lot with a standard twin choke, although it'll need re-jetting according to the modifications you make. To around 120-125 bhp is the benchmark, beyond that, you'll need twin DCOEs and, ideally, an electric fuel pump.
    Again that 244 cam's the watershed with low spec being fine with 40s, while the ultimate will need 45s. A remapped ignition curve is necessary with high-spec engines, meaning an Aldon-type non-vacuum advance distributor is the minimum.
    The ultimate for carbs, is managed ignition in either 2D or 3D form along with an ECU — systems from Weber Alpha cost around £500-600. The former plots 16 sites and is mapped to suit, whereas the 3D, requiring a throttle position switch and crank trigger, manages ignition values over 256 sites. This is the ultimate, short of throttle bodies and full engine management, and will serve to tame a highly cam’d engine, making it much more drivable on the road.

    The Block

    Bore Size
    +0.040 inch
    81.98 mm
    +0.060 inch
    82.48 mm
    +0.090 inch
    83.2 mm
    Whatever capacity you've got, the 711 is the one you want except in the case of the Fiesta. On the side of the block you'll find a T number cast-in — this is the number of that run of casting and goes up to 20. In theory, you need the highest number because it's said these are the thickest and therefore best for re-bore. Although there's no proof this is correct. Oversize pistons are available up to +0.090 inch (2.286 mm) which, together with a bore of 83.2 mm gives 1688cc also known as 1700. Re-bore / capacity steps are as follows:
    Blocks are now getting scarce although you can buy new ones from Burtons in both iron and aluminum. Of the ally ones they stock a replacement 711M, which will take a bore size up to 84 mm plus a Siamese version too (BPG100) for bores up to 90 mm. Meaning you can go as far as 2.4-litres with stroking.


    The bit that unlocks the power, the head is traditionally available in four stages:
    Stage 1 (standard 1300 valves)
    38.1 mm
    31.5 mm
    Stage 2 (standard 1600 valves)
    39.5 mm
    34.0 mm
    Stage 3
    40.7 mm
    34.0 mm
    Stage 4 (full race)
    41.3 mm
    34.9 mm
    According to the stage, porting and polishing is applied in varying degrees. Typically the seats will be recut to three angles for better flow, throats opened up and unleaded seats fitted. All good quality heads will have the standard guides removed and bronze ones fitted, tightening clearances up, while the valves should be upgraded too. Typically EN24 stainless valves with slim seats and waisted stems. Increasing in popularity though, are US aluminum heads. These make sense and are cheaper than you think — Burtons list them bare (with bronze guides and unleaded seats) for just £599. Valve sizes up to full race-spec are typical, although Burtons reckon they've fitted as high as 44.45 mm inlet and 38.1 mm exhaust. High lift cams mean that the valve train needs looking at too. The standard posts need to be swapped for steel ones, while the springs that space apart the rocker arms ideally need to be swapped for more positive location, otherwise they’ll upset valve geometry. The standard 1.54:1 ratio rockers are normally retained in all but race applications when roller tip components are utilized with ratios as much as 1.7:1 employed. This is ultimate stuff and not normally necessary.
    A regular head gasket is fine up to a 244 cam although an ARP stud and nut kit would be wise insurance. Beyond these limits a switch to Cometic type head gaskets is necessary.


    Your intended use should dictate your cam choice. However, there are two ranges of cams to choose from — the old-school, Cosworth A-Series or the current Kent / Piper. The difference is that the A-Series is all duration and low lift, meaning it's not emissions-friendly. Lobe overlap's high, dictating fuel being dumped down the exhaust, causing spit backs and poor economy. In contrast, the later cams will require better valve train components although these are best bought as a matched kit. You'll also need to pay particular attention to valve/piston clearance. For road use a Kent 234 is a good choice, although it won't give you ultimate power. However, it has good, low down torque. By contrast, the just-as-popular 244, comes in at 3000 rpm. It's a bit quiet till it kicks you in the back. This one tops out at around 8000 rpm putting it on the limit of standard cast components. For mild work in a light car, there's nothing wrong with the standard GT-spec cam — replicated to an extent in the Kent BCF1 although, this will give a touch more power. All the cams beyond the 244 are really for racing combined with all-steel components, right up to the Kent 272 with 9300 rpm potential. Cam drive needs to be swapped to Duplex past a 234 cam and ideally, you'll need a Vernier timing wheel to set the cam up on the dyno. Because of their narrow covers Fiestas can only fit single timing chains and of course Vernier’s don't fit either. So, offset dowels are the solution for this version.


    At the minimum, you need a GT tubular four branch manifold and 2 inch system. This will be good for power up to around a 235 cam hen you'll need to swap to larger primaries. Escorts have got it made because there's loads available off the shelf — the Ashley 4 into 1 manifold is a good one for use with bigger cams plus a 2 inch system. Anything else though, needs either a custom set of headers via companies such as Simpson exhausts or, if it's a Cortina Mk1 / Mk2 or 105E Anglia you've got, then 105 speed has its own systems off the shelf.

    Crank, Rods and Pistons

    The standard crank is cast iron and safe to around 7300 rpm although it will do around 7800-8000 in practice. However, before you test this, it's wise to have it balanced and tuftrided? Plus, before you do anything, swap the front pulley to a steel one. For big cam use — past Kent Cams 244 — a steel crank's a wise move these cope better with revs in excess of 8000 rpm. The standard 2737E rods are strong but benefit from a touch of lightening, long with Cosworth/ ARP rod bolts. Again they need replacing if revs are going to exceed 8000 rpm. A good range of steel replacements are available in both H and I-beam sections. Road engines can make do with regular cast pistons — also known as Hepolites, since that's the common make available. Common CR raising practice is to use 1300cc pistons, which will give a compression of 10.25:1. However, you'll need to check the valve pockets if you're using high lift cams such as the Kent cam/Piper range. If you need higher compression than this you'll need to switch to forged units. A set of Accralites typically give around the 11.5:1 mark. However, you'll need a bore size of 83.50 mm, dictating a very high T-number. You can actually go further still — as high as 86.50 mm bore, giving 1824cc but you'd probably need block liners or a trick ally block.

    Clutch and Flywheel.

    The standard cast flywheel can be lightened but only by an expert, steel ones are available depending on application. As far as the clutch goes, a standard-type is fine to around a 244 cam— although heavy-duty is advised. This though, is borderline because if you up the compression, you’ll need more grip. Helix do a fine range and will build a clutch to your spec.
    post edited by Greasemeup - 2015/05/10 11:57:54
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    Re: Tuning guides for Kent / X-Flow - Have you used them as a bible? 2015/05/13 19:26:31 (permalink)
    Another tuning guide, copied from PDF. This one has tables as well which dont format well on  a forum, I have a word / pdf if you would like.
    Ford Pushrod Engines
    By Paul Davies
    A popular engine to play with, Ford's pushrod powers many of our beloved retro cars. Here's how to get the best from it.
    In the near future retro-kids will ask about the facts of life. "Daddy what's a pushrod?" the miniature enthusiast will question. Born in a world of overhead camshafts, multi-valve cylinder heads and engine management systems, the mere idea of operating the valves through long sticks, pushed up and down by a single shaft buried deep in the engine, will seem just crazy. Retro-dad will sigh, put down his copy of Classic Anorak magazine, and begin. The BMC A-Series engine will be dismissed in a few words as "so 1950s" and then he'll go dewy-eyed as he tells the story about Ford's great range of four-cylinder pushrod motors. Generations of classic car enthusiasts, he'll say, owe it all to a dynasty produced from the late '50s through to the turn of the last century. Without these the Anglia, Cortina, Escort and others — not to mention such famous names as Cosworth, Holbay, Stewart, Clark (J and R) and Senna — might not have happened. Yes its old technology now, but the Ford fours can lay claim to being at the center of the formative ears of the classic car. And, more to the point, they're still out there in hundreds of thousands — waiting to be lovingly rebuilt and modified.
    Pushrod Fords slip comfortably into two sections: Kent crossflow engines and the earlier pre-crossflow units. And it all began in 1959. Ford's first small overhead  valve engine appeared in the radical, reverse-slope rear-window Anglia 105E and at almost the same time was slotted into the older style, four-door Prefect 107E.With cast iron block and cylinder head, and the inlet and exhaust ports on the same side as the cylinder head it wasn't revolutionary. But with 997cc developing 39 bhp it had the ability to rev well and it wasn't long before Formula 3 versions were producing over 100 bhp at 9000 rpm. By simply lengthening the stroke — changing the crankshaft and connecting rods — the engine grew to 1340cc for the first Classic and then an in-between 1198cc version powered the Anglia Super and the first Cortina. Ford, however, recognized the limitations of the three bearing crankshaft. In 1962 it produced a 1498cc engine with five bearings, which ultimately gave us the Mk1 Cortina GT and, with a radical head change, the all-conquering Lotus Twin Cam. A 1297cc five bearing motor was also produced for the Cortina. It was all-change in 1968. The Kent series appeared with crossflow cylinder heads (the inlet and exhaust ports on separate sides) and the combustion chamber built into the piston crown. With capacities from 940cc through 1098cc, 1298cc to 1599cc the engine powered Cortina and Escort models and in 1600 GT form became the basis for the world's most successful racing formula - Formula Ford. We know it best for its place in the Escort Mexico, and as the basis for the 16-valve Cosworth BDA. The motor's final UK appearance — in altered transverse form — was in the first Fiesta XR2, but production continued in South Africa until just a few years ago. Almost every engine hop-up merchant you can think of has got his hands on the Ford four at some time. Many have come and gone, but Burton Power has been with the engine right from the beginning and is still there, in llford (where London meets Essex), with an unparalleled mix of experience and the right bits. Naturally we thought it only right to visit them for the facts. Besides, Barry Lee, and crew, would probably never speak to us again if we went elsewhere. Nowadays a Ford Zetec or a Vauxhall XE may well appear to be the obvious choice for a upgrade in an Escort or kit car, but don't dismiss the original power plant. There's life in the old dog yet and the next few pages will tell you how to keep this one barking.
    Block and Internals
    The ingenious idea Ford had was to fix the bore size at 80.97 mm and get the capacity changes from varying the crankshaft, connecting rods and pistons. Except that doesn't mean all four-cylinder blocks are the same: early engines had three-bearing crankshafts before the stronger five-bearing units became universal (see our facts table) and larger capacity engines necessitated a taller block to accommodate the longer-throw crank. It's best to split the various units into pre-crossflow and Kent series crossflow engines.
    Early three-bearing units (997cc, 1198cc and 1340cc) had hollow crankshafts and while the first two engines are pretty robust the 1340 — like the Classic that came with it — is severely limited on revs. From 1962 all three engines standardized on a revised 109E (Classic) block with solid crankshaft, while the 1498cc block, introduced in 1963 with five bearing crank, was 0.67 inch taller. A later development of this block (with revised rear main bearing seal, larger big end retaining bolts and a diaphragm clutch flywheel with six fixing bolts instead of four) had a slightly stiffer casting and was used in the Mk2 Cortina 1300, as well as later 1500 and 1500GT engines. It's possible to alter the capacity of the three-bearing crankshaft unit by swapping crank, rods and pistons. However, care must be taken to ensure the resulting compression ratio is still workable. Retaining the existing head and fitting a 1200 crank/rod conversion in a 997 block will bring the CR up to a useful 9.5:1 (from 8.9:1), but a 1340cc conversion will need the combustion chambers opened out to achieve a lower figure. While a straight capacity increase will bring a little more power and torque, a swap to a 1500 or 1600 motor is preferable. The 1340CC engine must, anyway, be limited to around 5500 rpm. Further modifications and tuning of the pre-crossflow engines follow the same pattern as for the crossflow units and most of the equipment now available is for the later engine.
    Kent Crossflow
    The bores remained at the ubiquitous 80.97 mm dimension and the varying capacities were obtained by stroking. The 1600 block — with the number 681F stamped on the side — was 1.1 inches taller than the original 997 three bearing unit. Introduced in September 1967, the Kent engines underwent one major block change in 1970, when uprated versions were announced. The later block — with 711M marking — has a stiffer crankcase, strengthened mains bearing caps, larger diameter cam followers (13 mm instead of 11 mm) and a modified crankshaft end seal and is obviously ideal if tuning is planned. There is one other Kent block, the AX unit manufactured in South Africa. A
    version of the 711 M-type, this was a new thick wall casting that made greater over-bores possible and, because of its strength, was much sought after by Formula Ford competitors. Production of this (with AX on the side) ceased just three years ago. The 1600 block, especially in 711M form with stronger (flat) main bearing caps is good and strong with standard crank, rods and pistons that will handle up to 7500 rpm. With heavy duty connecting rod bolts 8000 rpm is possible. The best combination — without going to specialist steel competition rods — is to use Ford's 2737E rods and bolts. Beyond this figure the standard cast pistons, with a slot behind the bottom oil control ring, are the weak link. The Kent piston which contains most, if not all, of the combustion chamber is a meaty item, which has to deal with a lot of heat transference  and, because of its weight, is limited on ultimate rpm. Burton advises fitting Accralite forged pistons for high performance engines. These are available in a large number of sizes which, block willing, can take a 1600 unit out to over 1800cc. Normal 711M blocks will usually bore to 83.5 mm which, with standard crankshaft dimensions, gives 1699cc and an 84.0 mm bore (1720cc) is often possible. The much talked about 85.0 mm piston size (1760cc) is borderline on many blocks, while 86.5 mm (1824cc) is reserved for the old South African AX engine or Burton's own product.
    With good quality Kent blocks now becoming less available, Burton has had its own cast, in both aluminum alloy (light weight, good heat transference and the ability to easily off-set bores for greater capacities with 90 mm bore) and iron. These are made in both short (Lotus Twin Cam and 1500 pre-crossflow) and tall (711M) sizes. Burton can also supply Farndon manufactured steel crankshafts for the Kent engine, made with standard width big end bearings (26.85 mm) or with narrow bearings (23.7 mm) to reduce friction. Appropriate width (Farndon) con rods are required for the latter. Two points concerning original manufacture are worthwhile mentioning. Quite a few engines seem to have left Ford fitted with oversize mains shell bearings, presumably because the blocks have been line bored to rectify errors in alignment. If you don't spot this when carrying out a rebuild and fit standard size bearings, oil pressure will be depressingly low. Burton has had + 0.015 inch shells made to cover this eventuality. Secondly, the manufacturing threw up some blocks that were not accurately cast and (very) thin liners were fitted to allow a re bore. These will not stand a further re-bore and are suitable only for scrap.
    Cylinder Head
    Heads will benefit from the usual modifications to the ports and opening out of the combustion chamber around the valves. However, this will almost certainly have to be carried out on a customer's supplied head, as they don't pop up on parts shelves very often these days. The heads on all three bearing engines had the same size valves (1.27 inch inlet/1.18 inch exhaust) while the 1297cc and 1498cc five bearing motors had 1.43 inch inlet/1.18 inch exhausts. 1500 GT heads had 1.41 inch inlets and 1.245 inch exhaust and these can be used to good effect in the smaller capacity heads. Compression ratios can be raised by machining up to 0.080 inches from the head face and with the three-bearing engines it's possible to swap around. A 997cc head on a 1200 motor ups the CR to around 10:1 and a 1200 head on a 340 has the same sort of effect.
    Kent Crossflow
    The design is considerably more efficient than the earlier head, but also benefits greatly from gas flowing of the ports. While it is true to say that in all engines most (or all) of the combustion chamber is contained within the bowl in the crown of the piston, it's not quite that simple. Early (681F block) 1098cc and 58 bhp 1297cc engines had completely flat heads, but the 1300GT and the 1600/1600GT units had a partial recess in the head as well as the bowl in-piston combustion chamber. All post 1970 engines had totally flat heads and bowl-in-piston combustion chambers. Although the ports can be reshaped very little modification can be done to the recess-in-head chambers — the best heads to work on are the totally flat ones. One handy low cost conversion for 1600 engines is to fit 1300 pistons and rods, which will give a useful hike from 9.0:1 to 10.3:1. In this case it's essential to check there is sufficient cutout in the piston crown for the valves if a high-lift cam is being used. The two lower powered Kent engines (1098cc and 1297cc non-GT) had heads with 1.41 inch inlet and 1.24 inch exhaust valves but the 1300 GT and both 1600 motors had inlets increased to 1.5 inch diameter. Note also, valves fitted in heads with recesses were shorter than on flat heads. Whilst the 1.5 inlets are of reasonable size for a mildly tuned engine, you will need to go to 1.625 inch inlets for a fast road engine, but the GT exhausts are adequate at this stage. Race engines will use 1.8 inch inlet valves and exhausts of 1.5 inch. Early Kent engines had valves with 9/32 inch diameter stems, while the post-1970 up-rated version had 5/16 inch stems. Although Burton considers bronze valve guides as essential for a race engine, it advises against them for road use. They need greater lubrication so it's necessary to dispense with the valve stem seals, resulting in oil smoke. Both the Kent and pre-crossflow heads need hardened exhaust valve seats to run on unleaded without valve seat recession. Burton has also had its own flattop alloy cylinder heads manufactured for these engines.
    High capacity/high pressure oil pump is a direct replacement for the standard part and is essential for fast road use. A baffled sump will also be needed.
    Fitting a dry sump kit will eliminate oil surge and improve flow in competition engines. A remote oil tank will also need to be fitted.
    No major problems here as long as the block is in good condition with oil ways cleaned out. There should be around 30 psi on the gauge on tick-over and 45 to 50 psi at 4000 rpm. An oil cooler is often necessary and, to avoid a pressure drop when this is used, an uprated pump should be fitted. The four-cylinder Ford engine is a classic case for baffling. If you are staying with the standard item (i.e. not going to a full dry sump kit, which is certainly preferable on race engine), then any amount of hard cornering will result in oil surge. This could, in the worst case, cause the inability for the pump to pick up lubricant. Strategically placed baffling will prevent this. If you are fitting an engine that was original equipment in another vehicle, check the shape of the sump. Depending upon cross member location, the deep part of the sump may be at the front or the back and whatever you have has to be compatible. Don't forget dipstick location (front or back?) if you're swapping pans around.
    Camshaft and Valve Gear
    The single camshaft is mounted in the block and driven by tensioned chain from the crankshaft. The valves are operated by pushrods acting on rockers on a steel shaft. Ford made very few cam changes through the life of both the Kent and pre-crossflow motors. Apart from the earliest 997cc units, the same cam was used in all non-GT engines up to 1971 model year, when the uprated Kent engines were introduced and camshafts had wider lobes. The diameter of the cam followers was also increased. There have been many classic cam profiles for the engine, Cosworth's A Series being perhaps the best known. Although these are no longer available, cam specialists have developed new and more advanced designs, many based on well proven originals. Burton's own designs, many originally produced by veteran Ford specialist John Liveseley, are made by Kent Cams. Although many cams are available, the choice of rocker gear is limited. Burton can supply new rocker posts and shafts, but original Ford rocker arms are no longer available. However, roller rockers are, but these are quite expensive and a bit of an overkill for a road car.
    Pre-crossflow and 681F blocks are fitted with narrow diameter tappet stems, raised from 9/32 inch to 5/16 inch with the 711M block.
    You can get replacement steel rocker posts and shaft but only roller rockers are currently available.
    These Ford motors were around long before the electronic age. Original engines utilized either Zenith. Solex or GPD (Ford's version of the previous two) downdraught instruments. This was with the famous exception of the 1500 GT, which was fitted with one of the most marvelous retro carbs seen to man — the legendary, progressive choke, Weber 28/36 DCD. With two-stage operation the precision built Weber provided economy and torque at low throttle openings and then, as the secondary choke came in, worked like twin carbs. Often copied (anyone heard of the Nikki carb?) it was never beaten, but when the Kent 1600GT came along Ford got Weber to make them a special version, the 32 DFM with non-changeable chokes cast into the body. It did the job for Ford, but could not be easily re-choked and jetted to match varying stages of tune like the 28/36 DCD. Nowadays, neither the DCD or DFM is being manufactured, but if you're looking for an economical induction upgrade for a mildly tuned four-cylinder Ford you should consider the (still very much in production) Weber DGV, as fitted to late-model Escort Mexico and the Essex V6-engined Capris. But if you're totally serious, there's only one way to go. Once again put your hands together once again for Weber 40 DCOE or 45 DCOE depending upon state of tune. A pair of these beauties work wonders on almost every engine, Kent crossflows included. The twin side draught Weber set-up will take a Kent engine up close to the 200 bhp mark. To go higher than that a new set of throttle bodies and an appropriate engine management system is important and is, for best running, the only way to go.
    Exhaust Manifold
    With four exhaust ports, the 4-2-1 manifold works well on a road tune engine, while a 4-1 system will show top end gains on a fully tuned racing unit. Lowly production engines had cast iron manifolds, but GT engines had a fairly efficient 4-2-1 tubular system as standard. Ashley Competition Exhausts manufactures a 1500 manifold, which is available from Burton Power.
    How Much?
    Stage 3 modified cylinder head £558
    Set Accralite 83.5 mm forged pistons £500
    High pressure/high capacity oil pump £65
    Inlet manifold for Weber DCOE carbs £85
    A6 profile camshaft £100
    Steel flywheel, 6 bolt fixing (5.9 kg) £135
    Steel mains bearing caps (set of 5) £100
    Burton alloy cylinder head 882
    All prices include VAT from Burton Power for Kent 1600 engine.
    How Much Power Can You Get?
    Fast Road Tune
    Stage 3 head, ported and gas-flowed with 1.625 inch (41.3 mm) inlet and 1.24 inch (31.4 mm) exhaust valves, two-angle valve seats, double valve springs and new iron guides, Kent 224 (270 degree duration/10.6 mm lift) camshaft, 2 x Weber 40 DCOE carbs — 120 bhp at 6500 rpm.
    As above, with:
    Kent 244 camshaft (290 degrees/11.3 mm lift) — 130 bhp at 6500 rpm.
    Club Competition Tune
    Race cylinder head, further modified with 1.375 inch/34.9 mm exhaust valves and bronze valve guides, Accralite 10.5:1 forged pistons (standard rods, crank and
    mains caps), Kent 244 cam, 2 x Weber 45 DCOE carbs — 140 bhp at 7500 rpm.
    Race Tune
    Further modified head, with 1.8 inch/45.5 mm inlet and 1.50 inch/38.1 mm exhaust valves, all-steel crank, rods and Accralite pistons, A6 camshaft (336 degrees duration/10.2 mm lift), 2xWeber 45 DCOE carbs, steel flywheel, dry sump kit — 170 bhp at 8500 rpm.
    All above figures from Burton Power on Kent 1600 engine.
    Ford Pushrod Engines: The Facts.
    Block: Cast iron with three or five mains bearings.
    Cylinder head: Cast iron, four inlet/four exhaust ports. Crossflow, with bowl-in-piston combustion chamber with Kent series engines from 1968.
    Camshaft: Single, block mounted, chain driven and operating overhead valves through pushrods.
    Induction: Downdraught carburation, Solex, Zenith or GPD (Ford) with single, dual progressive choke, Weber on GT models.
    Year Capacity Bore/Stroke
    Pre-crossflow (three-bearing crankshaft)
    1959 997cc 80.97x48.4 mm
    Solex or GPD
    39 bhp
    1962 1198cc 80.97x58.16 mm
    48 bhp
    Anglia Super/Cortina 1200
    1961 1340cc 80.97x65.08 mm
    54 bhp
    Classic/Classic Capri
    Pre-crossflow (five bearing crankshaft)
    1966 1297cc 80.97x62.9 mm
    54 bhp
    Cortina Mk2 1300
    1963 1498cc 80.97x72.75 mm
    59.5 bhp
    Classic 1500/Cortina 1500/Corsair
    1963 1498cc 80.97x72.75 mm
    Weber 28/36 DCD
    78 bhp
    Cortina 1500 GT(Mk1 & 2)
    Kent crossflow (five bearing crankshaft)
    Classic Capri GT/Corsair GT
    1968 1098cc 80.97x53.29 mm
    53 bhp
    Escort 1100
    1968 1297CC 80.97x62.9 mm
    58 bhp
    Escort 1300/Cortina Mk2 / Capri Mk2
    1968 1297cc 80.97x62.9 mm
    Weber 32 DFE
    75 bhp
    Escort GT/Capri GT
    1968 1599cc 80.97x77.62 mm
    71 bhp
    Cortina Mk2/Capri 1600
    1968 1599CC 80.97x77.62 mm
    Weber 32 DFM
    88 bhp
    Cortina GT/Capri GT
    GT engines also featured larger valves, uprated camshaft and four branch exhaust manifold.
    NB: Early Mk2 Cortina’s f66-'68) were fitted with pre-crossflow engines.
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    Re: Tuning guides for Kent / X-Flow - Have you used them as a bible? 2015/05/18 19:17:02 (permalink)
    A little video of my car-


    I like the 'lumpy-ness' sound, sh*t video but I will put up another.

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