Triumph TR6
Matt tweaks the TR’S fuelling setup and fits some new boots
With the unpleasantness of a summer spent solving a drawn-out head gasket issue on the TR now thankfully behind me, the past few months have been much more enjoyable.
The ability to get in your classic and go for a drive without worrying about whether it will get you home again is easily taken for granted – suffice to say, I’ve really appreciated the simple pleasures of a top-down TR trip of late.
I’ve also finally been able to address a couple of smaller jobs that had to wait until now. The first of these was simple enough – changing the jet needles in the HS6 carburettors. When the TR first went back on the road in April 2019, it was fitted with a pair of BDM needles as a base setting to begin with. Unfortunately, the BDMS were not really up to the task and couldn’t keep up with the fuelling requirements of my engine. Low down performance was fine but, once you pushed on up into the middle of the rev range and onwards towards the top end, there clearly wasn’t enough fuel coming through, leading to nasty stumbling and generally rough running under hard acceleration.
As a short term fix, I’d swapped in the modified needles fitted to my 2500-equipped 2000 saloon.
I’d had similar issues with the 2000’s engine when it was fitted with a rebuilt and modified 2500TC back in 2012. A raging thirst for fuel and no great performance improvement over the original 2-litre engine was disappointing to say the least. Clearly, specialist help would be needed
Expert intervention
After receiving some advice from friends in the TR Register, I turned to Ron Harper of Ron Harper Classic Sports, near Middlesbrough. He tuned and optimised the engine to make the best of its performance components, but the chief upgrade he made was to modify the existing BDM needles to improve their fuelling rate. Ron cleverly used a micrometer lathe to remove material from half of the 16 fuelling ‘stations’ on the needle, chiefly those at the middle to top end of the rev range, richening them. It might sound like witchcraft,
‘The new BCH jet needles have made all the difference’
but the 2000 now effectively had bespoke needles and, when I collected the car, the transformation was clear. So much more power and, when I eventually came to do a ‘brim to brim’ road test, much better fuel economy, too.
So, in the run up to the 2019 Club Triumph 10 Countries Run, I removed the standard BDMS from the TR’S carbs and fitted the modified BDMS from the 2000. The two engines were built to a broadly similar recipe, so I was confident that Ron’s modded needles would make all the difference. Indeed they did – gone was the laboured bogging down under acceleration, to be replaced by a smooth run to the redline. So I was happy, we completed the 10CR without any issues… and I forgot to swap the needles back.
A little less procrastination
Almost a year later, I decided that I really better had sort things out once and for all. Using the online SU Needle Graph Comparator on the Minty Lamb website (mintylamb.co.uk), and with my dad’s help, I was able to plot the fuelling curve provided by the modified BDM needles and work out what standard needles came closest. As you can see on the above graph, needles BGW and BCH came out the closest. I elected to go for BCH and put an order in with Burlen Ltd, a company well-known for its expertise with all things pertaining to vintage and classic car fuel systems. I also ordered a new set of carburettor damper pistons with brass caps, as the standard plastic versions on my car had developed an annoying habit of unscrewing themselves, likely due to the vibration of the engine.
Once the BCH needles arrived, I quickly fitted them and rushed out for a test drive. The result? No discernible drop in performance compared to the modified BDMS, just as I’d hoped. Both cars are now fuelling properly and both can be fully enjoyed at any time. I’d call that a result.
New and improved
As a final flourish, I treated the TR to a new set of tyres. The ones on the car had plenty of tread and would more than likely have passed another MOT, but they were over 10 years-old, so they had to go. A trip to my local branch of Kwik-fit in Huntingdon got me a set of Continental Premiumcontact 6 in the same 196/65 R15 size that I already had fitted. They might not look particularly period, but the performance upgrade makes up for that. I’m impressed so far.