Converting my Triumph TR6 to Lucas Petrol Injection

It all started with a trip to the British Car Meeting at Mollis CH. At the way to Mollis, during a short brake at a gas station, I suddenly recognized that the engine lost a lot of oil. I had a higher pressure in the crank case as I had before. I knew the time has come to take the engine out of the car. After dismantling the engine I found out that the block must have been fitted with cylinder sleeves right from the factory, because I knew that the engine never had a rebuild except for my own rebuild approx. 17 years ago. As my plan was to use at least 76 mm pistons, the original block with the sleeves was out of the business and I had to use another block for my plan. The block for this project is an early Pi Triumph saloon block with the prefix CR. I also have the cross drilled crank for it, which I won’t use for this job, as my original crank from the TR6 block was already dynamically balanced and heat treated with zero wear after approx. 70k hard driven Km’s. The flywheel also has been lightened to approx. 8.3 kg with the ring gear.

PI_early limo block 1Pi_early limo block

Here are some Pictures of the parts that will be used for the rebuild.

TR6 cast slipper pistonTR6 cast slipper piston2TR6_cast slipper piston3H-Shaft rodTR6 Throttle bodies_Schaubhut_overhead linkage

Triumph TR6 race manifold
Triumph TR6 race manifold (Copyright

The new rods and cast pistons will reduce the reciprocating mass by approx. 1500 grams in total. Pistons are from a modern car and have been modified by company Wahl. Due to the slipper design they are very leight weight and withstands higher compression ratio’s than the AE or County pistons. Although the price for the pistons and the mod’s carried out costs almost as much as forged JE pistons. The exhaust manifold is a mild steel TR6 race manifold in very good quality with equal primaries and secondaries. The collector outlet size is 63 mm and requires a different intermediate pipe layout. I think it will be a duplex pipe I am going to use for it. The plan for the rear silencer is a transverse box similar to the Phoenix supersport silencer, but as a 63 mm straight through version. Unfortunately Phoenix will not do a one off of this type, so I have to find a solution for that. The TR6 Pi throttle bodies will be completely rebuild to a high standard from Ulrich Schaubhut, using roller bearings on both ends of the spindles. The rear TB will be converted to accept a second idle are valve. This should help to avoid cyl. no. 5 and 6 running too rich at idle.  The original air intake plenum will be increased in size from approx. dia. 80 mm to almost 110 mm and will be fed with air through  two original air filter boxes, one at its original position and the other on the lhs of the rad. The air filter boxes will be fitted with K&N filters of the type KNE9108. I think the two filter boxes and the enlarged plenum will further improve equal distribution of intake air for all six cylinders at speed when the throttles are wide open. The TB linkage is a home made version with uni-ball connectors and roller bearings for the lever spindle.  It is a overhead linkage, as the new manifold doesn’t leave enough space for a low mounted linkage. Pictures will follow later. Back to the block: The main bearing bores have been line bored to make sure it is in tip top straight condition (I had bad experiences with a second hand TR4 block in the past, were a crank seized at the running-in session). Also the cam journals are line bored. The block had to be milled down approx. 1 mm to deck the pistons. The little hump of my new pistons (aaprox. 1 mm) now protrudes into the chamber so that the outer face of the piston is decked with the block. This is how it looks now after painting. All the machining work has been carried out by an engine builder we are using almost 15 years now.  The assembly of the engine components into the block and the initial run in phase will be carried out by myself. I’ll probably use our test bed for the initial run in, so that in case of any issue I don’t need to take the engine out of the car. Further pictures will follow during assembling.


The cylinder head has been modified at the ports and the chambers. Valves are special flowed ones with a slightly bigger exhaust valve. The head work was carried out by Gareth Thomas. Rocker gear is converted to a roller rockers version to reduce valve stem wear. Compression ratio is 10.8 : 1. The camshaft is a GT 42A.

June 2014 Received yesterday my Y-Adapter  and two reduction pieces to route the intermediate exhaust pipes to the rear silencer. The adapter measures 63,5 mm to 2x 50,8 mm and it reduces to 47,6 mm.  The cross section of twin 47,6 mm pipes from Phoenix will be perfect to stay within the cross section size of the 63,5 mm manifold collector. Unfortunately the Y-piece needs to be reworked, to get the nasty welded 1 into 2 collector correct. See pictures below.


Just started to assemble the engine. The weight distribution of the Pistons is 2.3 gramm and rods are 2.06 gramm. After matching the Pistons to the rods the Distribution of the Piston rod assembly is 0.43 g.

Gewichtsangleichung Kurbeltrieb WP_20140617_005WP_20140617_007 WP_20140613_011WP_20140613_013

Fiddling around (just a trial fit) with the manifold and the enlarged plenum, to see if there is enough space between those two. It all fits very well, except for the support bracket that holds the plenum. I Need to fabricate a new bracket, so that it does not touch the primaries. The tubular race manifold is a top notch fit and even with this manifold the standard starter motor can be used.


Trying to figure out if the rocker geometry is correct. I have two different types of roller rockers to compare. That’s why you see two different types of RR’s at the pictures. The old type was from TLD and the new one is from Harland. I need to improve the geometry, no matter which type of RR I am going to use. There are different factors that influences the rocker geometry (rocker ratio; cam lift; cam base circle).  The roller tip axis and the shaft axis have to be 90° to the vertical axis when the valve is half way open (50-60% of the valve lift). This can be set up correctly by using shims below the pedestals. I Need to shim approx. 4 mm to get the geometry correct with the Harland rockers. The roller tip must roll over the valve stem plane face within the middle of the face. Otherwise the valve guides will wear out soon. This can be checked by using engineering blue at the stem face and rotate the engine with the rocker gear installed and set up. The push rod length is given after this work has been done. Below are some pics.

WP_20140619_003 WP_20140619_008

Rebuild throttle bodies are ready. The spindles are now guided with two bearings (front and rear), as well as shaft seals on both ends. Furthermore the rear throttle body has now an idle air valve, same as the front TB. The plenum has been altered with a braced in hose connection for the rear idle valve. I am really impressed with the quality of the rebuild. Below are some pics of the throttle bodies. You can also see the nice overhead linkage kit made by a friend, with uni balls and the shaft guided with roller bearings.

TR6 Throttle bodies_Schaubhut_2bTR6 Throttle bodies_Schaubhut_overhead linkage _bTR6 Throttle bodies_Schaubhut_3bWP_20140626_007

Trial fit of throttle bodies to the head. The plenum is now  finished and painted with wrinkle paint. Same paint used for the rocker cover. Unfortunately I used a little bit too much paint for the rocker cover, which causes that the paint wrinkles to much. I will probably paint the rocker cover again.


August 2014 I’ve played today with the custom throttle cable arrangement. I bought a throttle cable with inner POM tube. The 2 mm wire cable is stainless steel with 7×7 wires and is very flexible in this configuration. The attachments still needs to be optimized. Between the primary pipes the cable should route right to the back of the engine. I will probably use a bent pipe below the adjusting screw, so that the direction of the cable is guided by the pipe. The cable will be put into a heat reflective hose to avoid to much heat from the manifold. I’ve choosen this way of routing the cable below the plenum, because there are already so many hoses (fuel and air) routing all above the injection system. I still need to find a way, how to fit the choke cable arrangement. Below are some pictures from the trail fit.


December 2014 Installed a heat deflector shield below the throttle bodies and plenum. At the moment it is not yet the final shape of the shield, but all the attachments to fit the shield to the cylinder head and plenum have been realised as can be seen below.

TR6 Manifold heat deflector 1 TR6 heat deflector shield 3TR6 heat deflector shield 1

The engine is now fitted to the test rig for the first start. I hope to do the initial run before Christmas or latest before New Year. Just waiting for the crank pulley which will be fitted with a trigger wheel for the planned mapped ignition.

TR6_Engine test rig TR6 race engine lucas Pi TR6 fuel pump setup test rig

Just thought it would be good to show the difference of an original plenum and the modified plenum (see pictures below). These mods will help to get a better breathing balance at idle and more important at full throttle.

Modified enlarged plenum_1 Modified enlarged plenum_2

The „Christkindle“ brought me a nice gift. An AFR (lambda) controller with stepper gauge and Bosch LSU 4.9 O2-Sensor.  It is the Prosport Premium Series with output for ECU.  Also a warning light can be installed and set up for critical AFR.  Unfortunately the colour is either white or amber, but Prosport sell these gauges also in white/green, which would be the better choice for a TR6. The set came from No-Limits Motorsport

Lamda_Controller_ OT_Sensor

Also the crank pulley with installed trigger wheel is now ready for the crank. The pulley has been machined to fit the trigger wheel on the backside of the pulley.  I choose the trigger wheel with the size OD 6.5″ ID 5.25″. This is a very good fit as the OD is almost identical with the pulley. I had to machine the backside of the pulley by removing approx. 4 mm in width to a dia. 5.25″.  The wheel is attached with 6 allen screws. Also the pulley weight with the trigger wheel attached has been set identical with a std. pulley, to achieve the same harmonic balance. Although, the elastomer for sure is harder then it was 40 years ago, which has influence to the harmonics. I don’t know how critical this elastomer shore change is for the crank. Due to the missing tooth I thought it’s a good idea to balance the whole unit.

January 2015 The engine survived the first run of 20 minutes. I still need to check/balance the butterflies and sort out an oil leak at the Distributor. I think it’s coming from the O-Ring of the distributor. The original starter motor did not have problems to start the engine with a compression ratio of 10.8, which was a positive surprise.

February 2015 I will try to make my own air filter housing to be able to get a K&N-like twin cone airfilter with larger filter area installed. I thought about a filter and housing as shown in the picture below. The Housing would need to be modified and will be open at the front and at the cylindrical part to get as much air in as possible with least restriction and still looking close to the original design.

AIR_X_Twin_Filter TR6 Filter Housing TR6

Installed the Bosch fuel pump outside of the trunk at the left Hand side of the spare wheel well. I also moved the PRV to the same place. The panel is fitted to the body shell with silent blocks to isolate the pump noise from the body shell. Need to order a pre filter to be installed after the tank, before the Bosch pump. I think I will install this filter also outside of the trunk. The benefit of these mods will be less noise, probably less smell inside the car and better cooling of the pump. I am going to use a 4 mm/2 wire for the pump electric and a relay.  2,5 mm/2 would be to small for the pump’s approx. 16 amp. When everything is in place, I will fabricate a sheet metal panel, to cover the pump arrangement from stones and dirt which could catapult from the wheel.

Bosch fuel pump install

The pre filter and hoses are now installed. It’s a 30 µm  filter, good for up to 700 l/h flow rate. The feed from the tank to the filter and pump is made, using dash 10 fittings and stainless braided PTFE hose with ID 14,2 mm. The smallest dia. of the fittings is ID 12 mm. I think that should be good enough for the Bosch pump, which is not a good sucker pump, compared to the original Lucas pump.  Also installed the stainless steel Pi fuel  tank with integrated swirl pot and slightly higher capacity. The fuel outlet of the tank had to be drilled from ID 10 mm to 12 mm. Below are some pictures of the installation.

TR6 Pi Bosch pump
TR6 Pi Bosch pump
Stainless Steel TR6 Pi Fuel Tank
Stainless Steel TR6 Pi Fuel Tank

May 2015 The first test drive has been done with success  and the impression was as expected. Compared to the previous engine, the new engine pulls like mad. The torque at lower revs is quite astonishing and above 3500 rpm she is getting really wild. So far I didn’t rev the engine much higher than 4000 rpm, but it feels like the performance improvement starts above 3500 rpm. You can feel how easily it revs, which for sure is also part of the lighter pistons and rods.The test drive was done with the O2-Senor and AFR gauge installed. So I had the chance to see how the combustion behaves in different driving conditions. The AFR is in all conditions approx. 1 AFR to rich. I still need to do fine adjustments to the throttle plate balance and also the ignition. Ignition is still not the mapped ignition. I will install the mapped ign. not before next year. So first of all the balancing and mechanical ignition advance needs to be set up perfectly. Than I will do a second test drive and check AFR again. If its still to rich, the metering unit will be adjusted. The Bosch pump (from an Audi 2,3 Turbo) seems to work fine, except for partial resonance, probably coming from PRV or the fuel line between pump and PRV.

August 2015  Changed the running in oil and filter after 800 miles and use now Millers Classic Sport 20W50. Checked and reset the tappets. The clearance after 800 miles increased by approx. 0,05 to 0,1mm. I think this comes from bedding in tappets to cam and pushrods to tappets. I will keep an eye on it, to see if the clearance stays the same now. I have also altered the fuel settings, because the AFR was approx. 1 AFR to low at full load (WOT) and also at part throttle. I have adjusted the max. fuel screw to lean off combustion. Now the AFR figures are much better. Part throttle at 2000-4000 RPM = 14-15 AFR. AT WOT the higher the RPM, the higher is AFR, which is a bit strange. I think this could be coming from the Audi 2.3L Turbo Bosch Pump, which probably doesn’t deliver enough fuel at high load and high RPM. Part throttle at 2500 RPM when driving slightly uphill 15-16,5 AFR. WOT at 2000-3000 RPM = 12,5-13 AFR. WOT at 3000-4000 = 13-13,5 AFR. WOT at 4000-5000 RPM = 13,5-14 AFR. Misfire did not occur. Nevertheless, I will reset the max. fuel screw again to make it slightly richer, because at WOT and higher RPM’s the mixture seems to be a bit to weak and probably causes pinking. So far I am quite happy with the result and the TR6 goes now even better after the running in period and the metering settings. I hope I can make a little video clip of the car when driving in the next view days.

August 2015 update Adjusted the max. fuel screw again, to make it a bit richer. WOT at 2500-4500 RPM AFR=12-13. The higher I rev the leaner it gets. So WOT at 6000 RPM is 13,5 AFR. On the other hand at part throttle the higher I rev the richer it gets. At light load (for example uphill) and lower revs it goes lean up to 16 AFR. Applying a bit more load and it goes from 16AFR back to 13.5-14 AFR which shouldn’t be a problem at light load I think. I have also checked the compression of each cylinder and it looks very good.  I checked it dry with hot engine. No 1 and 2 = 207 PSI (14,3 Bar) / No. 3 = 203 PSI (14 Bar) / No. 4 = 210 PSI (14,5 Bar) / No. 5 = 217 PSI (15 Bar) / No. 6 = 215 PSI (14,8 Bar). Average is 210 PSI (14,5 Bar) and a spread of 14,5 PSI (1 Bar). The compression ration is 10.8 : 1. The compression and the spread between the cylinders  will probably get a bit better after some more miles, because the engine has only 1100 miles on it.

August 2015 update 2: Drove the TR6 now for 200 miles with the new max. fuel screw set up. Mainly at country roads and lots of small villages from Biberach to Augsburg and back. I didn’t use a lot of WOT, but mainly part throttle. In this condition the TR6 consumes 10.3 litres per 100 km, which seems to be very good. Spark plug colour also looks pretty good. Next tank full I will drive a bit harder with more WOT actions and also Autobahn at higher speed and see what’s the consumption at this conditions.



14 Kommentare zu “Converting my Triumph TR6 to Lucas Petrol Injection”

  1. Nice work! I am very interested in your throttle linkage fabricated by your friend. I need help with this as the accepted UK source for these is reluctant to make any more. Would your friend consider making another linkage for me? docdelete at gmail dot com

  2. hello and congratulations for all that work!
    I see that you have kept the original PRV.
    Don’t you have resonance in the hose?
    We are a few TR6 owners who had this resonance problem and we changed to a PRV with membrane which is best suitable for mounting Bosch pump.
    I’ll be as interested in your throttle linkage if your friend would consider making a small series …
    Thank you for your reply and good luck (when the car is finished!)
    Jérôme (from France)

    1. Hi Jèròme,
      yes, I also have resonance vibrations from time to time, but it’s not always present. Sometimes the resonance disappears, if I move the hose from pump to PRV up and down. I probably will also change the PRV to a membrane type PRV. Do you have a source for such a PRV?
      Regarding the throttle linkage kit, I will let you know if I can get my friend convinced to make a small series. How many would you need?

  3. Hi Jerome,
    I also am interested in your linkage system, I am going with efi and most of the webber based systems will foul the injector pressure tube. Please let me know if your friend is able to assist with this.

    1. Hi Greg,
      The distance from the throttle body face, to which the injectors are mounted, is approx 70mm to the overhead lever spindle. So I think you would need to move the fuel rail closer to the head side. Maybe with 90 degree elbow tubes.

  4. As I read the optimum TR6 engine! nice exhaust header! How did you succeed in contacting G Thomas and where did you order his 42A camshaft?

    1. Hi Frank,
      GT brought the cam personally. He visited me couple times.
      I am quite happy with the cam. Above 3500 it starts to go wild and at the low rev range it still has a lot of punch.
      Will forward GT’s contact to you by mail.

  5. Hi Michael,
    I am interested in the nice linkage kit you have
    is it possible to make it fit the late throtle bodies with some transformations to do?
    How do I get in touch with you?

    1. I think it would need a lot of mods to use this linkage for a CR model. They are completely different. Better try to find early throttle bodies, make your own linkage, or get in contact with Malcolm from Prestige Injection. I think he has kit’s available for CR models.

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