Triumph Spitfire - Troubleshooting Rough Running #3 | Roundtail Restoration 

Great video. I'm sure you will sort it out. I would love to hear the story about running without air filters. Good luck at the show.

Hi Chris, You can check if the engine is in need of fuel by slightly pulling out choke while on the road. Good luck.

original box filter is more effective as it acts as a cold air duct and feed both carbs equally well. the aftermarket sports air filter soak more heat and are more uneven in supllying fresh air. lots to learn, philip

Hey Chris, I had a GT6 with a similar problem that it would not continue to run and I finally found that the fault was with the rubber membrane in the Smiths Valve. It might be worth your while changing that out and see if it solves or improves the situation. Just a thought and I wish you lots of luck. Regards.

Good luck with this...sorry i have no suggestions.

If ever you suspect a carb issue check the ignition is 100% FIRST ! I am 90% sure your problem is ignition by the way it stopped suddenly. BTW that UK made distributor is not made in the UK, it is made in China. Not that it is therefore bad.

Chris, I feel your pain. My car would not rev well beyond 4K, turned out to be valve springs that had got weak over the years. Not sure if you’d changed yours during the rebuild.

Could it be the coil breaking down when it gets hot, and you loose spark or you get a weak spark ?

Does the electronic ignition still use the weights on the distributor? (The weights often stick at higher RPM.)

Hi, I haven't checked if you've actually sorted this yet but I had a problem with my spit that made it run rough: There was a screw in the distributer assembly holding on the... condenser? I think... And the flow of current that should have been going to the points was managing to earth onto the head of that screw intermittently. I found it by making the spark gap with a screwdriver and thankfully my friend looking over my shoulder pointed out that the spark that was created was finding that screw instead of always going between the contacts. Also, despite having disassembled and cleaned my carbs, once things had warmed up one of the carb pistons was occasionally finding some grip and not descending again, ruining the timing of the carbs. Just some suggestions, I hope you've sorted it!

Chris love your videos. I have a 67 Mk3 I tore down 8 years ago. Nut and bolt total restoration. I lost hundreds of photos when I bought a new iPhone ( thanks to their employee) I am installing a new wiring harness now. Problem is I don’t have any photos of how everything was routed so it is a slow go. Rear harness was easy but under the dash and engine compartment is where I am struggling. Could you send me photos of your wiring? I m ready to get this job done but need some visuals. Thank you for your help,Tony

Ignition switch…… or associated wiring. Plastic piece on the back of the switch can deteriorate, become loose and cause an intermittent issue.

Im having this exact issue right now and its confusing the hell outta me, almost like its running on 3 cylinders, i get the odd backfire. But under load looses power!!

Chris, you may have already checked, I haven't seen the previous streams yet but, have you checked the gas cap vent?

Hi Chris, I do hope your pb is only ignition/carb related but the fact that cyl n°3&4 seem always down on power, all the symptoms you have might be caused by a very tiny crack in the inlet manifold water pipe, going through n°3&4 inlet duct below when the cooling system pressurizes and metal expands. Similarly it could be tiny coolant passage through the head gasket on cyl 3 & 4. Good luck!

Is the intermittent related to only rpm? Can it be induced with speed vs rpm? Any quicker to intermittent on rough road vs smooth road? Rpm could be related to load but also related to vibration. Battery and alternator output up to snuff? On big jets we’d do a “ hand over hand” inspection of wire bundles hunting for intermittent situations. This included tapping on connectors with say the butt of a screw driver, flex a wire bundle at various locations or even use freeze spray or judicious use of a heat gun trying to initiate a change in the status quo. I found a lot of faults with the freeze spray at connectors. 99% of all Lucas wiring issues are bad grounds or dirty/ corroded connections. Probably all obvious to you, just brainstorming with ya brother….

Very long shot, but when I bought my Spitfire it had been run very infrequently over the preceding few years, and the float bowls were full of some sort of sediment which I assume must’ve resulted from fuel degradation (it had a filter before the pump). It might be worth emptying them fully with a syringe as you’d only need a tiny bit of muck to reduce the fuel flow to the jet. Small chance you have the same issue as you’ve done a pretty low mileage since rebuild.

Hey Chris get you a gallon jug gas put beside that car take your fuel pump and hook it straight into it and rev the 0:07 car up and see if it's doing what you're doing now it sounds like you're sucking trash up in the tank and higher RPMs did you use the original gas tank I can't remember when you was building that car hopefully that might help you have a good day

Could it the exhaust has a blockage and when you run at high RPM you get a lot of back pressure. Just a thought. 👍

There is an old saying about British cars - "most carburettor problems are electrical", suggesting that most running issues are related to the ignition faults. You have eliminated distributor and plugs but what about the coil? I had a very similar problem where the car would run well when stationary but once moving would start to miss and backfire. The problem was the ignition coil breaking down when warm and under load. It might help diagnosis if you have another coil you could substitute. Good luck.

Is there a diode on the rotor?

And check the fuel filter, how old is the gas?

it odd that it seems to run fine, then it goes rough after a while. Does it ever go back to running smooth without shutting it down and letting it cool off? My gut tells me that its the coil again. it could also be something like a tiny vacuum leak that gets worse as the engine warms up, maybe a loose intake? I know that is what the propane is for. Maybe even a borderline bad plug or wire. I have confidence you will nuke it out eventually.

fill up with oil black plastic scru on top of carburators

Chris what I was trying to get to on using a gas tank beside the engine I can't remember if you bought a new fuel tank or just reconditioned the old gas tank but you could be picking up trash and about 3,000 RPMs with a vibration of the car. And what happened with the higher RPMs the vacuum sucks the trash to where the gas line is in the tank

it seems to me to be a coil problem. try the tr four coil on the spitfire and at least eliminate that issue.

replace the coil I've have had this problem twice and both times it was the coil.

How frustrating!

I own british bikes, not cars. But my long distance youtube guess is the fuel tank is not vented. Try removing the gas cap and take it for a quick run and see if anything changes.

I had a 64 years ago. I sure miss it. I notice that the windshield wipers on your 66 are opposite from my 64. The wipers rested to the left and would leave a smear right where I looked through the glass. It seems that later years they inverted them to rest to the right. Am I right?

Unless it is the video I can see the missfire on your timing light. Try running a jumper direct from the battery to the coil. This will eliminate any problem with the ignition power supply to the coil.

Just finished watching the video, I have very little doubt right now that you dont have enough fuel to support more than 3500 rpm. Colapsing fuel line, plugged tank vent, fuel line to small... For quickest check, try running with a temporary tank. That eliminates everything but fuel pump (least likely thing I think). Good luck and keep us informed.

had the same problem....... webercarbs