No sooner had I got the car running better than it had ever run before, another carburettor related problem arose. I was getting the car out for a blast around the local country lanes when I heard the sound of liquid pouring from underneath the engine – one or more of the carburettor float chambers were overflowing.

Schematic diagram of the SU HD8 Carburettor.

I’d had this issue several years ago and it is generally caused by one of the following:

• a sticking float needle caused by debris or build up of fuel gum or ‘varnish’ in the needle seat housing (53)
• incorrect heights of the float levers (54) operating the float needles
• a sunken float (50)

In light of the ethanol fuel issues, you could add the deterioration of the float needle’s vulcanised tip to the list.

I had previously checked and adjusted the height of the float levers so it all pointed to some sort of issues with the operation of the float needles. The height of the float levers can be set by simply turning the lid upside down so the lever is holding the float needle in the closed position. The correct height should allow a 7/16” (or 11mm) bar to be inserted so the float levers forks are just touching the bar. Any adjustments can be made by bending the lever.

Setting the float lever height

All three lids were removed allowing a visual check for the buoyancy of the floats and the lever heights re-checked. All was as expected so the float levers were then removed by withdrawing the pin hinge to enable the needles to be removed.

The front carburettor’s lid disassembled revealed a broken needle tip

The vulcanised tip of the front carburettor’s needle was only partially attached. It looked like at some stage in the past it had been glued back in place and during the inspection just fell off. Again this could have been a result of having ethanol in the fuel which has degraded the tip over time. The other two needles looked fine and so were retained (a poor decision!).

A new needle and seat housing arrived from Burlen Fuels a few days later. The replacement needles now have a Viton tip which isn’t affected by ethanol.

Replacement needle kits now have a Viton tipped needle to overcome ethanol problems

The three lids were refitted back on the car and the ignition key turned to switch on the fuel pump to check everything was now resolved. It is an understatement to say that the now familiar sound of fuel pouring from underneath was a disappointment!

One problem is the ends for the overflow pipes are hidden away next to the oil filter. They’re only clearly visible from beneath the car so it is tricky to diagnose which carburettor is at fault and then get back into the car to turn off the ignition before too much fuel has been discharged.

In the end I had to remove the air filter so I could position a mobile to video the overflow pipes while operating the ignition from within the car. The results were very conclusive – it was the middle carburettor that had the issue …..

If you’re going to do a job, do it once and do it properly! I think it was an eagerness to get the car back up and running that I’d taken shortcuts and had assumed the broken tip of the front carb was the only issue.

Also if the ethanol fuel had been the cause of the issue then it was only a matter of time before the other two would fail. So a false economy only replacing one. Therefore two more needle kits were purchased so it shouldn’t be an issue in future.

I’ve now also taken to using Ethomix Ethanol Corrosion Inhibitor Additive (E5/E10 Fuel Protection) and VSPe Power Plus Fuel Additive whenever I fill up the tank.

It’s been almost 10 years to the month that the restoration was completed. Due to other issues NNF 10H hasn’t be in use for almost 18 months and it has just had the occasional starting. A plan had been hatched to head off to the Le Mans Classic in 2027 with John and Martin, who had helped install the IRS. This was a good excuse for a planning meeting and an opportunity for Martin to see the fully restored E-Type. But first I needed to ensure it would make it to the meeting venue!

It had been in the back of my mind to get the car properly tuned as I had felt it had never been running brilliantly since the restoration was completed, even though it had been through the hands of several E-Type specialist garages. I mentioned this to John who made some enquiries with his motorsport contacts and the advice was to take it to Ray West of West Tuning at Thruxton race circuit. It was reassuring that Ray is clearly in demand as it was over 4 weeks before he had any availability to fit my car in.

The first task was to give the car a full service. In fact the first task ended up being just to get it running! The battery had been on a CTEK trickle charger however one or more of the cells had failed in the time it had been laid up. The delay while a new, replacement PC1200T ODYSSEY Battery 12V arrived was put to good use to buy all the servicing items; high temp grease, grease gun, spark plugs, coolant, oil filter and the various engine and transmission oils. I kept with the Odyssey battery as it has a high cranking output even though the current one had failed.

I could tell things weren’t going to go smoothly – as soon as it arrived the new battery was fitted and the car fired up to bring it out into the open to work on. Well it would have fired up had the fuel pump still been working. I had previously upgraded the internals to electronic actuation and my assumption was the circuit board had failed. The only other possibility was that the internal coil had burnt out which would require a new unit.

I had acquired and renovated a spare pump during the restoration but couldn’t find it anywhere! The only other option would be to buy a new one although I found all the suppliers only had them on back order. Back to plan A …. and after an extensive search I managed to find the spare pump, which had been hiding in plain sight!

The assumption is the circuit board of the SU Fuel pump has failed

The cooling system was given a good flushing out by opening the radiator and engine drain taps and placing a running hosepipe in the radiator filler until the water coming out of the drain taps was clear. The only other issue I had was being able to grease the outer UJs for the rear half shafts as I couldn’t get the gun on the grease nipple. I think I need to swap them to angled nipples.

The final task was to tune the car before taking it off to the tuner! I managed to get a fairly good base setting and then tweaked this to improve the running but all I achieved was to make things a whole lot worse. I couldn’t understand what I was doing wrong.

To make matters worse one of the cooling fans failed while tuning. I’d also acquired spare cooling fans during the restoration so set about rebuilding a replacement fan asap. However the trip down to Thruxton was early the following morning. I just had to get the fan fitted (untested) and the car into a state of tune that would at least get me there. At 9:30pm the night before I called it a day – fingers tightly crossed it would make it there without incident, as it was in a shocking state of tune. The revs just rising when the clutch was depressed. The only way to reduce the revs was to use the brakes to slow the car down while in gear.

As John kindly mentioned when we rendezvoused early in the morning en route to Thruxton, at least I’d set a very low bar for Ray to improve on! The car was put on the rolling road to give Ray an idea of what he was playing with. Even with my ‘tuning’ attempt it was pleasing to still be showing 208.5bhp. Some way off the published 265bhp claimed by Jaguar although real-world figures were typically in the 210-220bhp range. I’d not had the car on a rolling road before so it was somewhat unnerving having the engine rev’ed up to the red line.

The gas analyser was giving a lambda reading of around 1.2 (lean) at low revs but the desired 1.0 (Stoichiometric) higher up the rev range, which is the exact fuel/air mix for complete combustion. After some deliberation and reviewing the SU carburettors needle graphs, Ray decided we needed to swap over from UM to UK needles to correct the mixture at low revs. Fortunately Burlen Fuels who manufacturer the needles were only 14 miles away in Salisbury so we were able to collect new needles and resume after lunch.

The profile mapping of the SU needles

Time was pressing on when Ray noticed the jet in the rear carburettor had dropped which implied something was wrong internally with the jet bearing and jet assembly. It was decided to leave the car with him to investigate. The outcome the following day was the jet bearing had both cracked, therefore allowing the jet to fall, and was worn. It was more oval than round and would need to be replaced. This would necessitate replacing the jet bearings in the other two carburettors so they are all in an identical condition.

To be continued ….