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    Triumph TR6 / Ford 302 V8 Conversion

    A tight fit, but a fit never the less. This is a shot of a later stage of installation fitment. Except for the headers, there is plenty of room. Note how the heater hoses mate up perfectly with the TR6 bulkhead fitting. Not visible is the stock heater control valve, located at the left rear of the manifold.

    ENGINE CHOICE

    Although nearly any engine can be made to fit, there are three choices that come readily to mind – The Buick/Oldsmobile/Pontiac/Rover aluminum block 215 CI V8, the ubiquitous 350 Chevy small block, and the 302 Ford Windsor. There are pros and cons to each, but either will work quite well. In making a choice, about five factors come into play – outside dimensions, weight, displacement, cost, and availability of parts, particularly “speed equipment.”

    DIMENSIONS: Surprisingly, both the BOP/R and the Chevy engines are wider than the Ford, while the Ford is a bit longer than either of these. Even though the chart below dosen’t show it, I have seen other sources which give the height of the BOP/R and the Chevy as an inch or so taller than the Ford (and my measurements of the Buick V6 tend to support this). I have seen good examples of TR6s with BOP/R, Chevy, or Ford engines, so either of the three can be fitted without too much difficulty.

    WEIGHT: The BOP/R is the lightest of the three, while the Ford is about 90 pounds lighter than the Chevy. What may not be expected, though, is that the Ford engine, with aluminum heads, is actually lighter by about thirty-six pounds than the original six-cylinder Triumph engine.

    Width Length Height Weight
    BOP/R 26 28 27 320
    Ford 24 29 27.5 460
    Chevy 26 28 27 575
    Chevy/w alum heads 26 28 27 525
    Ford/w alum heads 24 29 27 424
    TR6 22 29.5 25 460
    Buick V6 26 28 29 412?
    The first three entries came from a recent issue of “Street Rodder” magazine, and are reasonably accurate, except for the weights. Without knowing precisely what ancillaries are included, a real comparison can’t be made for weights. Length can vary tremendously by the choice of water pump and pulleys, and height will depend on the intake set-up. The fourth entry was obtained by subtracting the weight savings of aluminum heads from the third entry. The last three entries came from my own measurements, and are very precise. The weights given include everything required to make the engine work – starter, alternator, flywheel, clutch, intake, carburetors, exhaust, distributor – everything except oil and water! In this trim, the weight for the Ford in entry two becomes 519 pounds, from actual measurement! The BOP/R and Chevy weights will most likely go up a similar amount in the same trim.

    DISPLACEMENT: The displacement of the BOP/R starts at 215 ci, and goes up to 275 ci in the later Rover versions. Stock, the small block Chevy displaces 350 ci, but can be punched out to 400 or so if so desired, while the Ford is 302 ci, and can be stroked to 347 without problems.

    COST: Cost figures are hard to come by for the BOP/R, but the Chevy will cost a fair amount less than a comparable Ford, just because of the greater popularity of the Chevy. I would estimate, for lack of actual data, a cost differential of about 10 to 15 percent between the Ford and the Chevy.

    In my personal opinion, when all four factors are evaluated, the Ford engine comes out as the engine of choice. Width and cost rule out the BOP/R, and the additional 90 pounds rule out the Chevy. The engine I am using in my conversion is the aluminum head GT-40 engine from Ford Motor sports. It comes with the high performance B-303 cam, and is rated by Ford, based on dyno testing, at 320 HP. This is with EFI, so I may be getting a little less by using dual quad carburetors, but in a TR6, this still comes out to be just a little under eight pounds per horsepower – more than enough!

    engine right

    Right side of the engine, with a clear view of the motor mount and the custom crank pulley. The engine mount will be turned 90 degrees from shown and welded to the Triumph frame.

    Engine left

    Left side of the engine, showing the custom alternator mounting details and the engine mount. I haven’t decided whether to use two round air cleaners or one oval.

    I know I would be better off using fuel injection, or at the least, a single carburetor, but I wanted the “look” of the dual quads simply because when I was younger, dual quads were the hot setup. This car is as much about nostalgia as it is anything else. To compensate for the excessive carburation, I am using a progressive linkage. When putt-putting around town, I will be using only two barrels. When I get my foot into it, all eight barrels will be hosing gas into the engine.

     

    ENGINE LOCATION/INSTALLATION

    The principle goal in locating the engine should be to get it as far back and as low as practical. The firewall and legroom concerns limited how far back I could place it, and ground clearance limited how low I could go. By placing the battery in the trunk or other location, the engine can be placed a couple of inches further back than I did, but one of my design goals was to retain the stock battery location. Trunk space is far too valuable to me to lose any for the battery, and I don’t like the looks of a side-mounted battery under the hood. In the final configuration, the bottom of the pan is flush with the bottom of the frame, and the stock TR6 frame brace runs between the fan and the engine. I have about 1 ½ inch clearance between the fan blades and the radiator. The centerline of the crankshaft is about 2 inches lower than in the stock TR6 engine, and the center of the intake manifold is about 1 1/2 inches to the rear. All and all, not a bad arrangement.

    The only significant problem with the Ford engine, when compared to the Chevy, is the auxiliaries sticking out the front, as the result of the distributor and the oil pump being front mounted. Almost all Ford engines have a long crank pulley, which would strike right smack into the TR6 steering rack. This problem can be solved by moving the rack forward, but I was afraid to do this for fear of messing up the steering geometry. The one guy I have talked to who took this approach says he has a little bump steer, but not so much that he can’t live with it. Personally, I want none, so I moved the engine back as far as I could and made a pulley myself to fit (I have a friend with a machine shop – very handy). You could always have a pro shop make one for you if you don’t have access to a machine shop yourself.

    Crankshaft pulley

    This custom made pulley was required to fit the engine into the engine bay, without interfering with the steering rack. There is approximately 3/4″ clearance between the pulley and the rack – just enough to allow for changing the fan belt without moving the steering rack.

    I’m using a ’77 Buick pulley on the water pump, one I just happened to have laying around (no longer available, unfortunately), and a GM alternator. I put the alternator on the driver’s side of the engine to reduce the overall engine length, which meant I had to custom make all the support brackets. Using the Buick water pump pulley as the starting point, I made the crank pulley to match, and then followed through with the alternator mounts to get the alternator to line up with everything else.

    Alternator mounting details

    Not shown are the chromed spacers over the bolts, which were made from the left over piece of the Borgenson steering shaft used to modify the steering setup. The brackets have since been chrome plated, and look sharp!

    For motor mounts, I used 2′”X 2″X 3/16″ angle iron, with 2″X 2″X 3/16″ tube steel welded perpendicular to the angle iron. I notched the end of the tube steel at a 2 1/2-degree angle to match the engine/driveline angle, and had a pro weld it for me. I cut a nice curve into the outer ends of the tubes so they wouldn’t look too homemade. I then bolted a rubber-biscuit type motor mount bought from a Street Rod shop to these. I used pieces of 3″X 3″X 1/4″ tube steel welded directly to the frame, and the rubber biscuits bolt to these.

    I set the engine as low as I could without having the oil pan drop below the frame rails. This requires me to put a small bulge in the hood, about 1 3/4″ max, which I kinda like. Not big enough to draw the attention of joy-riding teens (they’ll never know what hit ‘em!), but enough that a TR6 enthusiast would notice. Sorta like a “Danger” sign!

    Engine mount

    My home made motor mount! The piece of tube steel at the bottom will be welded to the TR6 frame rail, 90 degrees from shown here.

    I modified the oil pan (dual sump) to eliminate one of the oil drain plugs. The front plug fell right over the crossmember. It would not have been hard to get to, but the oil would drop onto the crossmember during an oil change, and would make a mess, unless I used some kind of wacky funnel or something. To get around this, I cut the center of the pan out and replaced it with a fabricated piece of sheet metal. The front sump now flows into the rear sump and I can drain the oil just by the rear plug. This also adds a quart or two to the oil capacity – not a bad thing to do. It was just one of those things that will make the car a little easier to live with later.

    The engine could, I believe, be dropped another inch or so by further modifying the oilpan and redoing the oil pickup. This, and using a single carburetor with a small air cleaner, would eliminate the need for the hood bulge. Doing this would require modifications to the frame brace and further modifications to the front crossmember, but certainly not a difficult task.

    Ford “Shorty” headers will not work, because they exit to the rear of the engine and dump right into the firewall. I bought a set of “Block huggers”, but they didn’t hug the block close enough – about 3/4 inch more is needed. Also, the tubes at the top did not clear the body. I cut the tubes off, leaving only a 1″ stub, and will have a muffler shop custom fabricate the remainder. I have mocked them up with 1 1/2inch heater tubing, so I know they can be fitted. I also bought a Ford Motorsport compact starter for more clearance. It has the added advantage of having the solenoid on the starter instead of on the fender (I intensely dislike the Ford fender mount solenoid!)

    The mufflers will fit in the space provided for the stock muffler. I am not just sure yet how the exhaust pipes will run from the headers to the mufflers, but I don’t foresee any major problems. They may run just a little low at the front, till they clear the engine, but after that, I think they will tuck up between the frame rails like the stock setup.

    TRANSMISSION, CLUTCH, AND DRIVETRAIN

    For clutch actuation, I am using a Tilton hydraulically operated throw-out bearing. They slip over the trans input shaft, and operate like a slave cylinder. I am using a T5 transmission from an ’88 Mustang for mock-up purposes, but I have later model with a higher torque capacity for actual installation. It is larger (no doubt!) than the stock unit, but it is actually lower than stock. I cut down the transmission tunnel quite a bit. There will be room to mount electrical components over the tunnel if desired.

    Transmission comparisons

    Guess which one is stock? Note the tilt of the T5. The mounting flange, though, is level, and fits perfectly to the TR6 mounting pad. The rear crossmember will have to be moved a bit to match.

    transmission mount, top    transmission mount, bottom

    Two views of the transmission crossmember mount, made from a piece of 1″ X 2″ 16 Ga. steel tubing. Note the holes for access to the bolts. The transmission mount is a stock TR6 piece, with mates perfectly to the T5 mounting holes.

    The ’88 is rated at 265 lbft, while the new ones are rated at 330 lbft. I haven’t purchased the Tilton unit yet, so I don’t know if the TR6 MC will work, or if I will have to use a Tilton unit. The cost is roughly the same, since I will need to rebuild or replace the one I have. Using the stock Ford cable clutch actuator should be fairly simple if you want to go that route. TR4s used a different arrangement for the clutch MC, with the MC running to the rear instead of to the front as on the TR6. It should be fairly easy to get the parts from a TR4 from a junkyard, and make an adapter to connect to the Ford cable (I say this, having never tried it! It may not be so easy, but worth looking into). The only real problem with this is the space taken up by the throw-out arm at the bell housing – it will cut into the foot room quite a bit.

    HANDLING AND BRAKING CONCERNS

    A lot of people are concerned about the additional weight of the Ford unit over the stock TR6 engine and the effect it will have on handling and braking. As a matter of fact, with aluminum heads, water pump, and intake manifold, a lightweight performance flywheel, and the small starter, the Ford engine/transmission combo weighs 25 pounds LESS than the stock TR6 engine and transmission. A stock Ford engine with iron heads and intake will weigh about 90 pounds more, or 65 pounds more than the TR6 engine. I plan on using up-rated shocks, springs, and sway bars front and rear, but don’t plan on any other serious modifications. Even though the car will be capable of much higher speeds, since I will be driving it only on the street, I will not be going much faster. And, as the car will not be any heavier, the stock set-up should be plenty adequate. The typical “Street Rod” uses a 10″ rotor on the front, and the hi-po rods use an 11″ rotor. The stock rotor on the TR6 is 10 7/8″, so, considering that the average street rod weighs over 3000 pounds, and the TR6 weighs only 2500, the stock brakes don’t look so bad. According to the brake experts, a street driven car should have 200 square inches of brake swept area per ton: The stock TR6 has over 250! Never-the less, I am looking into using Wilwood 4-pot calipers to match the braking power of the 11 inch drums that I got with the Ford rear axle (compared to the stock 9 inch units). I will either have to improve the fronts or add a proportioning valve to reduce the rears to get the proper front/rear bias. I don’t want the rears to lock up first in a panic stop!

    Brake drums

    The stock 9″ drum is placed over the 11″ Ford drum for comparison. There should be no trouble hauling down a lightweight TR6 with these, especially with upgraded front discs to match!

    REAR END

    Depending on the power output of your engine, and its intended use, the stock rear end may well be adequate. When these cars were raced, the engines produce around 200 HP, so they are known to withstand power levels of that magnitude. Even with only 200 HP, though, drag racing would probably shorten their life considerably. With 200-250 Hp, and driven moderately – no dumping of the clutch at 3000 RPM – the stock rear should live a long, healthy, life. I know of at least two cars that use the stock differential, one that has been on the road for over ten years with no problem. As an economy move, the stock rear end could be left in place and up-dated later as time and money permit.

    Installing a complete, narrowed, IRS unit from a Jag or a Corvette, or even the aluminum IRS set-up from a Lincoln MKIII, should not be a terribly difficult job, but would be very time consuming if you did it yourself. There are several companies that specialize in narrowing the Jag and Corvette units for use in early Ford, Chevy, etc, street rods, so the tread width would not be a problem. As is, though, the stock TR6 frame will not work with these units, as there is no “kick-up” in the frame in this area as there is in the street rods. The entire rear section of the frame would require reconstruction.

    For drag racing applications, a live axle, utilizing a four-bar set-up, will work very well. There are several companies specializing in this set-up, so getting parts would be no problem. This configuration can be set-up to handle over 1000 HP – or more – so it would be bullet proof in this application.

    There is one serious drawback to the last two options, at least for my application – both will cut into the trunk space and/or the passenger compartment quite a bit. Depending on intended usage of the car, this may or may not be a problem, but it is something to be considered.

    For my application and intended usage, I decided to use a narrowed Ford 9-inch axle. I am using the complete rear suspension set-up – springs, bushings, hangers, etc. – from a TR4A, live axle version. It is almost a bolt-in operation, requiring only a little welding at the rear hangers. I cut the rear spring/bumper/body mounts from a TR4A and replaced the same units on the TR6 with them. It was an incredibly easy task. All that was required was to grind down the welds and remove the tube crossmember from the TR4A mounts, and grind the TR6 mounts off of the TR6 frame. I slipped the TR4A mounts over the TR6 crossmember, and welded them in place. If you can not find the front hangers, and they are scarce, fabricating them should not be a major task. The rear hangers are the same whether the TR4A is an IRS or a live axle version, so they should be easy to come by. If not, it would be very easy to modify the TR6 mounts by welding on metal tabs with the extra holes required for the rear spring shackles.

    Rear axle

    What it takes to handle over 300HP! Compare the Ford 9″ to the stock differential in the foreground. The Ford 9″ measures 52 inches from drum to drum.

    There are many companies which specialize in narrowing Ford axles, so getting one will not be a problem. I bought mine from Currie Enterprises in California, complete with brakes, brake drums, and a Truetrac limited slip differential. This is a gear type differential, which supposedly doesn’t give the understeer effects that a clutch type does. I will maintain the stock TR6 bolt pattern (4 X 4 1/2″), but I will use ½” studs, rather than the 7/16″ stock size. This will allow me to use one spare tire instead of two, and will let me use Panasport wheels, which is my preference.

    The only thing I don’t like about this approach is the limiting effect of the leaf springs. The outside-to-outside measurement for the springs is 41 1/2″. Using 215/65R15 tires, the tread will measure 50 3/4″, compared to 49 3/4″ stock, and the outside sidewall-to-sidewall dimension will be 59″. This is 2″ more than stock with the same size tire, so the fenders may need to be flared a little. A little I don’t mind – I just don’t want a large flare.

    If you have the time, before you get to that point, you should start reading “Street Rodder” magazine; they usually have one or two cars using the Jag or the Corvette in each issue, and there are lots of advertisers, whose ads can be quite helpful.

    STEERING

    As with any engine swap, re-routing the steering can be a bit of a problem. I shortened the outer steering column to where it only protrudes about an inch beyond the firewall. The inner column is in two parts -a smaller diameter inner shaft, and a larger diameter hollow outer shaft. I cut the outer shaft in two, just above the collar for the steering wheel locking mechanism (if you wish to keep the lock mechanism, you could cut just below the collar). I then cut a Borgenson steering shaft, with splines on one end and the other end plain, to the right length. I used my friend’s machine shop to turn down the plain end to fit inside the hollow shaft, and had it professionally welded.

    Steering shaft

    In the upper photo, the top piece is the Borgenson shaft, turned down, and the lower piece is the stock TR6 shaft, cut in two. The Borgenson shaft was inserted into the TR6 shaft and the two pieces were welded together, bottom photo.

    I cut the outer column close to the firewall to keep the angle as shallow as possible to eliminate interference with the left hand cylinder head. At the other end, I used a Borgenson U-joint, with splines to match the TR6 rack on one side and the standard 3/4″ on the other. I could not get by with only three U-joints, so I used a double U-joint in the middle of the steering assembly. This required me to use two Heim joints. I drilled a hole in the shock tower for the lower Heim joint, and drilled a hole in the inner fender for the upper joint. The Borgenson catalog says not to use sheet metal for a support, but I discussed this with the owner of Borgenson (a very nice guy, and very helpful, BTW), and he said it would be no problem as long as I had the first one solidly mounted. There is a lot of shock transmitted to the steering gear when you hit a bump, and the sheet metal just won’t stand up to it. I am also using the solid aluminum steering rack mounts, so that should reduce the shock to the fender mounted Heim joint to near zero.

    It’s too early to tell for sure, but the steering seems just a tight, and as free, with the four u-joints as it did before. I don’t expect a problem. Once again, looking to the street rod fraternity, multiple u-joints are used regularly with, apparently, no problems.

    Steering mock-up

    Photo taken early in the mock up process. I used wooden dowels to make the steering line up determination. Notice also the new radiator, which will be replaced with a Griffin aluminum cross flow unit.

    COOLING

    For cooling, I had a thick core, five-row radiator made to the same dimensions as the stock unit, but I was not happy with this idea. I have now bought a Griffin aluminum cross flow radiator, with two 1- inch tubes, and a larger surface area. This will require me to notch the frame rail and build a new support structure for the radiator. My original plan was to use a mechanical fan, but I will now be adding an electric unit with a thermostatic control. I prefered the mechanical fan for reliability – if the engine is running, the fan is also – but the mechanical fan didn’t mate up real well with the radiator, as it stuck up about two inches or so over the radiator, and building a fan shroud would have been a bit difficult. With an electrical fan, there are several ways for it to fail, leaving me stranded with an overheating engine. A blown fuse, a bad relay, a bad wiring connection, or just a bad fan motor, will do it. As long as the car is moving at a reasonable speed, it will be OK without the fan, but Murphy’s law being what it is, the most likely time for a failure is in the middle of town, in a traffic jam, in August! The electric fan will provide more efficient cooling because I will be able to locate it better with respect to the radiator than I could the mechanical unit.

    Fuse panel

    What a mess! When completed, the wiring will be up out of the way of the fuse panel. Note the Aluminum switch panel used in place of the original switch plinth. The switch to the left is for the headlights, the middle hole is for the hazard switch, and the ignition switch is on the right.

    ELECTRICAL

    The electrical work involved should be fairly straight forward, unless you go the route I did. I removed the fuse box and relays from under the hood, and made a new fuse/relay/flasher panel and mounted it up under the pedal box, where it is out of sight, yet easy to get to. (I am a retired electrical engineer, so this part of the job was the easiest for me). This panel has eight fuses, two flashers, and five relays.

    The fuses are of the aircraft/industrial type. The cap twists to lock and unlock, and the fuse comes out with the cap. I used these simply because I like them. I don’t know of any real advantage to them for automotive use. I used eight fuses because that is one less than the number required to properly fuse the car. In addition to these eight, I used, by design, one in-line fuse in the lighting circuit. My wiring is not that much more complicated than stock – Triumph just used six fuses too few!

    There are five relays, one each for the starter, driving lights, and fuel pump, and two for the alarm system. I built in the wiring for the alarm system, using an eleven-pin connector. When I install the alarm unit, I will cut off the wires that come with it to a length of just a few inches and terminate them in the other side of the eleven-pin connector. Then it is just a matter of plugging it in. If I ever change out the alarm unit, no changes to the wiring will be required. This approach also has the advantage of having all the alarm wires wrapped in the wiring harness along with the other wires.

    The two flashers are, of course, for the turn signals and the hazard flasher.

    I made my own wiring harness, using the proper colors and sizes for the TR6. I used a mixture of connector types; some were typical British types, and some were of the typical American type. The selection depended on the application: where connecting to, for example, the stock TR6 turn signal switch, I used British “Bullets.” Where connecting to the headlight switch, which is a GM unit, I used an American type. Connections to the hazard switch – vintage Radio Shack – are soldered.

    GAUGES

    With the exception of the tachometer, the original gauges can be used, although I would not recommend using the ammeter, if your car has one. The stock ammeter is a 30-amp unit, and must be replaced with at least a 50-amp unit, which will probably not match the other gauges. I would replace the ammeter with a voltmeter, which is a very simple task. The fuel and water temperature gauges can be used as is, and adapters are available to connect the mechanical oil pressure gauge to the ford block. A new speedometer drive gear will be used at the transmission to correct the speedometer readings. The TR6 tachometer is a mechanical unit, and a Tach drive distributor for a Ford engine is very expensive. Of course, one option is to leave the stock Tach in place for appearances, but just not hook it up. Adapters will be needed to connect the transmission to the TR6 speedometer cable, or to connect the Ford speedometer cable to the TR6 speedometer. Although not common, adapters should be available from some of the major instrument shops.

    Dashboard mock-up

    I like those gauges! The dash panel used here is a plywood mock up just for construction purposes.

    I used a complete set of Autometer Phantom gauges – black bezels with white faces – and made my own dash from a piece of solid Oak. The Tach and the speedometer are 5 ½ ” units, while the smaller gauges are 2 5/8″. Because of the size of the smaller units, I had to make my own dash. The dash has been the biggest headache so far. Only minor mods were required to the metal dash backing to use the larger gauges, but the woodworking involved in the wood part were significant for me. Cutting the glovebox door out of one piece of wood, and not having a large or uneven gap was a real chore. Of course, the dash and door could be made from two pieces, and covered with one piece of veneer, which would greatly simplify things.

    Finished dashboard

    This is the actual dash. The discoloration in the center is from the flash unit on the camera. It looks much nicer in person!

    There is another option available now, which wasn’t when I bought my gauges. Autometer now makes gauges in the Phantom line that fit in the same holes as the stock TR6 gauges. Using these, with the larger Autometer Tach and speedometer, should allow you to use the stock dash. The large Autometer units will fit in the stock openings, but they are a “loose” fit. There will be about a 1/16″ gap all around, in the recessed area.

    BODY MODIFICATIONS

    I don’t plan any body modifications other than that required to make the swap. I am quite happy with the car’s lines as is, and don’t know of anything that I think should be changed.

    Most likely, I will have to flare the rear fenders, and the hood will require a slight bubble. The bubble will need to be about 1 3/4″ high at the front, and about 3/4″ high at the rear to clear the air cleaners. I made it 19″ wide and 26″ inches long for appearance sake. I could get by with a much smaller bubble, about 7 X 13, and only about 1″ high, but I don’t think that would look as good. I am not planning on having a scoop in the bubble. I intend for the sides to slope gently into the hood itself. I very carefully cut the 19 X 26-inch piece out of the hood and I will use it for the top of the bulge, as it already has the correct contour. I made hammer forms from pieces of oak, and I will form the front, rear, and the sides over these.

    At the firewall, I had to do a fair amount of cutting, and I will have to fabricate a sheet metal replacement. Even though I had to make fairly large cuts, very little legroom is lost, and none where it counts.

    Engine bay modifications

    Not as bad as it looks! A narrower battery and a fair amount of sheet metal work will be required, but very little legroom will be lost. This is the only surgery required to fit the engine (notice that the inner fender “wings” were cut down for more room – white arrows). No cutting of the floordoards was required.

    The red arrow points to the crossmember notch. A new cover will be welded in place, and tube steel reinforcements will be welded to the bottom for strength. The crossmember will be strong enough to serve as a jacking point for the front of the car without damage.

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