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NARROW FAN BELT CONVERSION
An Aussie Method

This is a co-operative attempt by two TR Register members (John Buck & Rick Fletcher) to solve the problem of converting the existing wide B section belt on the TR to a modern narrow 11mm belt. We know that you can buy this gear off the shelf but it is very expensive and we wanted to see if we could do it on the cheap. Like all such conversions, it takes away from the originality to some extent so is not recommended for the purist. However if you do want to use a readily obtainable narrow belt and change a few other things, then this may interest you.

By the way - this article is written in good faith but neither of us are motor engineers so be careful - we are simply revealing what we have done. [I have had the conversion on my car for over 5 years and done over 50 thousand kilometers including some at racing speeds and all the modifications behaved perfectly - Rick Fletcher 2004]

Things that you need to GET, SCROUNGE or have MACHINED are highlited in BOLD

To assist in the conversion here are some photographs

THERMO FAN

The first thing that is a big change is the existing crankshaft mounted fan. We don't use it. In fact my car ("Bluey") has been running since 1970, over 30 years, without the fan and without a harmonic balancer (the motor is balanced). Use a thermo fan mounted behind the radiator. Bluey used to have a Kenelow fan which had several "losses of smoke" and two re-winds. I eventually accepted the advice proferred by many and purchased a cheap thermo fan off a wrecked Japanese car and fitted that.

The one I used has 4 short stubby blades and 2 flanges or brackets extending one from each side of the motor body. 2 U-bolt clamps, each holding a vertical strip of metal were attached to the tubular spacer between the suspension towers. This made suitable mountings for the fan.

CRANKSHAFT

The crankshaft requires a narrow pulley. John is now an Australasian expert on every available form of harmonic balancer which may remotely come near to fitting a TR! Many of you have also helped by contributing suggestions and telling us what you have used. We chose to use a common variety Holden (GM) harmonic balancer which is CHEAP (particularly if you can get an old one to trade-in) and can be obtained from Auto One type shops. The one to use fits the Red, Blue or Black motors and is an HB17A Harmonic Balancer

Of course nothing is simple - a previous Prime Minister had something to say about that. The front of the cranshaft on the TR is 28.6mm in diameter. The Holden H/B is 28.5mm in dia and was meant to be pressed on. We don't want to do that so you will need to remove the offending 0.1mm (4 thou) from inside the balancer. Get a machine shop to polish it out for you.

The key way is a perfect fit for the TR so some things work out OK. The correct seal to use is an imperial size which is available at bearing suppliers. It is:

          2.5" x 1.75" x 0.375" 

(mine came from Metropolitan Industrial Supplies - Penrith  02 4731 2005)

Before you take the original pulley off, set the motor to Top Dead Centre (pistons at top of stroke - distributor rotor pointing to #1 plug - both valves closed on #1). The keyway on the crankshaft should be facing down. Remove the pulley and then the timing cover and Woodruff key. The original seal needs to be removed but not replaced with the one listed above just yet.

A spacer is needed behind the Holden balancer as its nose is too short. The spacer needs to be:

          28.6mm Inside Diameter x 8mm thick x 45mm OD (OD is approx - not critical)

This would be a simple job for a machine shop. It is important that the two faces are exactly parallel.

 There is a shouldered stud just above the crankshaft which supports the timing cover near the seal. Temporarily remove it. It will (just) foul the Holden H/B when fitted so grind a few millimeteres off the top and thin-down a nut to suit. Refit the stud, slide the 8mm spacer on the crankshaft (it can stay there) refit the Woodruff key and try the balancer in place - it should just clear the stud. Set the timing cover (no seal) back in place and you will note that the triangular TDC marker collides with the harmonic balancer - bend it up and crank it back out so that it clears the balancer. Temporarily refit the original pulley and adjust the motor so that it is again at TDC. Carefully remove the old pulley and refit the balancer which can now be marked for TDC - I filed a tiny nick at the edge and filled it with white marking pen.

Remove the balancer and timing cover. Check that the cover is "true" particularly where it mates against the engine front plate. This would be a good time to check the timing chain and almost certainly to replace the tensioner. The seal can be carefully fitted with a smear of gasket cement  around the mating surfaces (I use "Permatex Blue silicon gasket maker"). Coat the seal lips with oil so that they will not be damaged during assembly. Prepare all the bolts and studs for reassembly - watch a couple at the top which go straight into the block - use a small smear of Permatex Blue on the threads when you assemble them to prevent oil leaks.

I made a thick paper gasket (0.8mm) for the cover simply to get the seal running further along the nose of the balancer - if you do that then fit a couple of fibre washers to the shouldered stud. Use a thin smear of Permatex Blue to both sides of the gasket. It is important to initially LOOSE fit the timing cover to the engine plate relying on the dowels and machine screws to roughly locate it - don't forget to fit the thinned nut to the shouldered stud. The exact location is guided by very carefully sliding the balancer through the seal which then accurately "centres" the cover. Tighten the bolts progressively and not too much (14 -16 ft.lb)

The balancer is in place and now only needs to be bolted-up. I used a crankshaft bolt obtained from a Vanguard in a wrecking yard. You could try Noel at Sportscar Spares - Girraween - 02  9631 9279. He certainly has the tab washers which need to be fitted behind the bolt. I used an additional plain washer behind the head of the Vanguard bolt as it did not seat correctly against the tab washer. Bend 2 of the tabs against the faces of the bolt. Bottom end finished!

WATER PUMP
Note: see box below ** for another simpler alternative

The pulley we used was from a wrecker. It is from a Toyota Corolla 3K motor produced from 1968 into the '80s. The extreme Outside Diameter of the pulley is approx 125mm and the pulley is approx 70mm deep if sat on a flat surface and measured to the front face. The pulley runs on a 24mm dia hub and the 4 mounting holes (7mm) are equi-spaced on 40mm PCD. Should cost about $5 to $10.

This pulley requires a hub to be machined according to the dimensions shown in the accompanying drawings.[See Drawing] Use 4 x 1/4" UNF high tensile machine screws 3/8" long to attach the pulley to the hub.

If you are inordinately lucky, you will be able to remove the old pulley, clean the shaft and key and be able to replace the new hub and pulley with no fuss. The manual says to use a small 3 leg puller - ones I do usually require dynamite or nuclear energy to release them! Hopefully you won't have damaged the seal but if you do, at least from here on it is a piece of cake to remove the pump as it now possible to remove the pulley by the simple expedient of undoing 4 screws. Take the opportunity to replace the bolt holding the water pump to the block with a stud. Don't use overly thick nuts to hold the pump on as the new pulley runs very close to the nuts. A thin smear of Permatex Blue or Red (higher temp) is all that is required to seal the mating surface.

** President John Pike's report
on his variation to the conversion

As mentioned in the lastmagazine, I was converting Thud's electrical system to be looked after by an alternator, as per the instructions devised by Rick Fletcher and John Buck. I can now report that the conversion is complete, and the fact that Thud conveyed the Pikes to and from the Concours without losing any of the smoke in the electrical department would indicate that the conversion was a success.

To recap, the afore-mentioned Messrs Fletcher and Buck had spent a considerable amount of time and effort in designing a suitable alternator modification to the TR, including the use of a narrow fanbelt to replace the more difficult to obtain (and change by the side of the road) standard belt. The story of their exploits appeared in the magazine of April 1999, and I was interested in finding out whether a less than mechanically gifted person could successfully undertake the conversion.

The job essentially consists of three separate elements - changing the harmonic balancer on the end of the crankshaft, replacing the water pump pulley, and consigning the generator to the Prince of Darkness spare parts bin.

My experience revealed that there were a couple of divergences from the instructions, which I'll cover here.

Step one was to change the harmonic balancer. As the apron and radiator were already off the car this was not a difficult process. Mind you, the thing that made it even easier was that Graham Brohan happened to be visiting, and was instantly pressed into service. We followed the instructions, with one exception, relating to a stud just above the crankshaft, which supports the timing cover near the seal. Rather than remove this stud and grind a few millimetres off it, we left it in place and massaged it with a cut-off disc attachment on a Dremel. I have to say that the Dremel is a fabulous bit of kit, enabling one to do some very precise work that would be almost impossible with more conventional type tools. It took no more than a minute or so to cut a 3mm slice off the stud, without disturbing its seal, and about the same time to cut a similar amount off the appropriate nut, after mounting it in a vice.

Next item on the agenda was the water pump, and here the Fletcher/Buck instructions were not required at all. Following advice from Bob Seaman, a Triumph 2500 pump and pulley were used. [Rick Fletcher - the mounting holes are not a direct replacement as they are on a different PCD - Pitch Circle Diameter, but in the correct radial position. However the impeller diameter is correct and the pulley is designed to take a thin belt so the previously described machined pulley hub IS NOT REQUIRED. What is required is for the holes in the flange to be slotted towards the outside of the flange as per John's following description. There are cheaper alternatives to the Dremel but in each case the fibre-glass miniature cut-off wheels are the best to use, albeit more expensive.] Slotting the attachment bolt holes was a piece of cake, courtesy of the Dremel again, and after applying a light smear of Permatex red the new pump snuggled easily and neatly into place. [Note: be careful to ensure that the impellor is centred and not fouling the pump casting when relocating it as the slotted holes don't provide an exact alignment. It should rotate without touching the casting.]

Finally, we came to the alternator itself. This was fitted without drama, but caution is required when tightening the attachment nuts. The instructions said to tighten the first nut so that the alternator is quite stiff to move. I found that doing this tended to distort the mounting bracket on the block, so my approach was to tighten the nut until the bracket was about to bend, then fit the second, locking, nut. The original instructions also indicated that the adjusting arm needs a bit of a tweak, and sits behind the top lug of the alternator. In discussing this with Rick, it turned out that his adjusting arm was somewhat second hand, whereas the "proper" arm is virtually an exact fit and falls into place in front of the top lug.


ALTERNATOR

We chose to change to an alternator, preferably Bosch which have a much thicker mounting bracket than Lucas. One with the correct arrangement and shape of mounting bracket is the Bosch BXD1242 which was used on the Holden Astra, Datsun 180B and 200B and the Nissan Pulsar (81-87). It should be possible to get one from a wrecker but we purchased new ones for long term reliability. They are rated at 60Amps which allows for plenty of additional electrical accessories. The regulator unit is also simple and cheap to replace.

To mount this alternator, all that is needed is a replacement front spacer - as per attached drawing [DRAWINGS TO FOLLOW] and a bolt. Again, the spacer is a simple machining job. It replaces the generator front mounting bolt which goes through the front engine plate. The new spacer locates into the hole in the engine plate and is drilled to accept a 10mm bolt (not 3/8") which needs to be 160 - 170mm long and with 2 nuts and lock washers. You may have to dig around to find one as there are plenty 150mm long but not so many in the 160 -170 range. The rear hole of the existing generator bracket need easing out to 10mm with a file.

The mounting bolt goes through the front alternator bracket, through the machined spacer and engine plate, through the rear alternator bracket, through one nut and lock washer, through the rear bracket and finished with a 10mm nut and lock washer on the outside. Tighten the outside nut fairly tight so that the alternator is quite stiff to move. Then tighten the inside nut against the bracket to lock everything in place. Notice that the rear alternator bracket and tube piece is (correctly) free to move.

I salvaged the adjusting arm (water pump casting to alternator top arm) from the one on the old generator which had been considerably butchered in the past. A visit to a wrecker might find a better type - needs to be a bit straighter but still nice and thick like the original one. A tiny cranking of the bracket by a millimeter or so was necessary to get everything true. The bracket fits behind the top lug on the alternator.

The correct belt is an 11mm x 1005  (eg Bosch 11A1005). The final solution does have a slight misalignment between the water pump and balancer pulley of a few millimeters but this has not proved to be a problem. The water pump and alternator pulley should run in the same plane as they are relatively close.

The alternator has a built in regulator so some simple changes are needed at the old regulator. At the voltage reulator join all the thick wires together - ie. A1, A and D. I removed them from their terminals, made a 3 way joiner out of thin brass sheet and taped them in a compact bundle. Take the thin wire off D and join it to the thin wire off F (tape these as well). Leave the Black earth wire on its terminal (not doing anything now). Get your auto-electrician to check - charge rate should be 14V.

Good Luck - Rick Fletcher and John Buck