Upgrades and Conversion Kits

I have owned my TR5 for 12 or so years. It has been on the road rain or shine all of that time and is a proper workhorse. My TR3 was a complete body off resto, undertaken myself using most of the old body and chassis as templates to make new. It has been on the road for 4 years. In normal years both cars go round Europe at least once; myself and my wife in the 3 and friends or family in the 5. Both are well used so you get to know what works and what doesn’t.

These are a few of the upgrades and conversions I have come up with over the years to make TR life a little easier.

Countershaft Bearing Upgrade

Countershaft Bearing Upgrade

As well as being fiddly to replace, non-rigid bushes can do little to ensure repeated synchronised opening of all 3 sets of butterflies, which is required to ensure uniform mixture across all cylinders.

So, replace those wobbly, imprecise flexi-bushes with a pair of self-aligning sealed ball bearings. We can also supply oilite bushes press fitted into new standard countershaft brackets. These work fine but take a bit of tweaking to get aligned so that the countershaft turns freely.

Both types are straight replacements using existing fixings, so completely reversible. Precise and uniform throttle response every time you put your foot down.

Countershaft bearing upgrade – Oilite bushes £45 / Self-aligning sealed bearings £65

Twin to Single Choke Cable Conversion Kit
TR5 TR6 CP twin to single choke cable conversion kit

TR6 Choke Cable – Twin to Single Choke Cable Conversion Kit CR and CP Models

Replacement twin choke cables are hard to find. They cost over £100 when they are available, and they are poor quality. This conversion kit includes a high quality* single choke cable that connects to a modified choke fast idle cam. A link cable connects the fast idle cam to the metering unit. Watch video of the system working here. Metering unit enrichment and fast idling remain independently adjustable. It all attaches using existing fixings so is completely reversible. Should your single choke cable break in the future, similar replacements are available on eBay for as little as £15.

TR6 Twin to Single Choke Cable Conversion Kit – £85

*The choke cable supplied in the kit is specially made to our specifications by a well-established cable-maker in the Midlands. The cable has a square knob with original logo, chrome bezel, multi-stranded Bowden inner cable with soldered end, PTFE lined outer cable and either twist and lock or friction lock operation. The only thing it doesn’t have is the removable knob.

TR6 Choke Cable – Single CR & CP Choke Cable

A longer version of the above cable for those that are not bothered about the fast idle and just want to connect directly to the metering unit.

Single CP and CR Choke Cable – £45

TR6 CP and CR Improved Throttle Cable

Most owners will have probably experienced issues with the infamous crimped ferrule on the outer cable slipping resulting in limited throttle operation. Despite this being an issue for many years, it still happens with new cables.

Another issue with standard cables is they are excessively long, resulting in unnecessary bends in the cable under the bonnet. This results in the cable binding and problems with idling.

Rather than the usual recommendations such as the use of cable ties etc to prevent the ferrule from moving, we dispense with it altogether. Instead, we terminate the outer cable where it passes through the bulkhead and fit an additional cable adjuster.

Our cable is also shorter with a single curve from the bulkhead to the throttle linkage to avoid the problems with binding.

Cables are made up with new or original fittings.

Improved CP Throttle Cable – £45

CR to CP Throttle Linkage Conversion

TR6 CR to CP Throttle Linkage Conversion

The throttle linkage system fitted to the CR cars was probably deemed a great success by the cost engineers when they came up with it. When everything was new they probably even got them all synchronised and working as they should.

The linkage fitted to earlier cars had more moving parts, and was therefore more expensive to make, but it did have the advantage of allowing each of the throttle bodies to be adjusted individually to take up any wear in spindles, swivel posts etc.

Refurbished CR Throttle Bodies with new CP Throttle Style Spindles Allowing the use of CP Countershaft Assembly

This conversion involves the installation of CP style butterfly spindles in CR throttle bodies, allowing the CP countershaft and choke assembly to be used. If you want your original setup to operate as it was intended, this is the way to go. Bearings can also be fitted to the butterfly spindles that will eliminate any future wear for an additional £200.

If you change over to CP throttle bodies, you are then into new springs and recalibration of the metering unit, (with or without a change of cam), due to the different bore of the throttle bodies themselves.

This conversion is a simple spanner job, and all of the metering unit settings are unchanged. It all fits using existing mountings in the throttle bodies so it is completely reversible. Note – if bearings are installed, throttle bodies have to be counterbored and would require bushes fitting to revert to standard setup. To see a video of the system working click here.

CR throttle bodies with conversion spindles and bearings, CP countershaft and rods (outright sale) – £1350*

CR throttle bodies with conversion spindles and bearings without CP countershaft and rods (outright sale) – £1080*

*£150 trade in for your old throttle bodies if they are suitable for reconditioning.

CP Throttle Body Bearing Upgrade

CP Throttle Body Bearing Upgrade

The butterfly spindles in the CP throttle bodies are smaller diameter than those on CR cars. They wear significantly at the lever arm end where the force is applied to open the butterflies. The wear is then transferred to the centre of the spindle. The end farthest from the lever is the pivot point and wears the least. Despite the absence of a bushing, the bores in the castings do not wear much at all.

Play in the butterfly spindles affects the basic operation of the butterflies, and allows increased airflow into cylinders 2, 4 and 6 at tick over, which can do little to help smooth idling.

Our manifolds are fully refurbished with slightly oversized new spindles as standard. However, we can also fit a sealed bearing to the lever end of the butterfly spindle, preventing wear for good.

CP Throttle Body Bearing Upgrade 2

Those on my car have been in for 10 years and have easily done over 50,000 miles with no detectable wear. They are, however, on their second set of lever arms and linkage rods. So, if you are having this conversion done, you really need detachable lever arms as fitted to early cars to get the full benefit. Ours have the detachable levers, allowing lever arms and spring replacement as required without the removal of butterflies and spindles.

CP Manifolds Refurbished with Bearing Upgrade (outright sale) – £750*

*£150 trade in for your old manifolds if they are suitable for reconditioning.

Long Distance Touring Upgrades

Some of the upgrades I have made on my own cars are specifically for long distance touring abroad. These include:

Twin switchable Bosch fuel pumps, submerged in swirl pot, that has its top in the boot and its bottom fitted with cooling fins between boot floor and chassis leg.

Cooling the pumps with the fuel is fine, but it’s much better if you can also cool your fuel as you drive. After an hour thrashing the car along the A351 to try and avoid rush hour traffic in Strasbourg a few summers ago, we arrived right in the middle of it.

This setup kept us going in stop-start traffic at 34C around the ring road, with less than a quarter of a tank of fuel. Had we fried a fuel pump, a flick of a switch would have brought the backup pump into action and got us going again.

PI dashboard comprising fuel air ratio gauge, vacuum gauge and electronic fuel pressure gauge.

The fuel air ratio gauge constantly monitors the mixture the metering unit is sending to the engine. The vacuum gauge then allows you to know where you can adjust the metering unit if you are lucky enough to have a PI test rig!

The electronic fuel pressure gauge is just that, an instantaneous readout of the fuel pressure. I generally run my car at 100PSI to take some of the load off the fuel pump. The PI dash enables you to see how the engine is running at all times – you are a human ECU. You can even use it to make adjustments on the road. If you want to drive over the Stelvio Pass, you lean up the metering unit at the bottom so you need the choke out to keep the fuel air mixture in range, and you slowly put the choke in as you go up to maintain the correct mixture, pulling it out again as you descend. You can then use the gauges to reset the metering unit once you are at the bottom.

These upgrades are a bit involved and of limited interest, so are not available in kit form. If you are interested, let me know using the form here and I can let you know what’s involved.