Lamborghini Miura - Tracing a running fault to a 17th century invention | Tyrrell's Classic Workshop

[Music] [Music] [Music] hello and welcome to another tyrells classic workshop this time round we're looking at this car here another lamborghini miura and this car we restored we did a full ground at restoration on it which was completed about four years ago something like that it's come in for effectively a first service because of covert and one thing another and it's got a running fault on it which we're looking into i think it's stale fuel actually it's spitting back through the carburetors on light throttle when you're driving it it has all the sort of symptoms of stale petrol which is not surprising because it's been stood round but it's a lovely car it's finished in this blue speciality which uh the owner and myself went to a great deal of trouble to nail for him so that it was exactly right and it suits the car perfectly as i say that we've done a complete rotisserie ground at restoration on this car it has come in with a running fault and let's see if it's just as simple as stale fuel well this is really curious because we've drained the fuel tank we've put fresh fuel in it we've run it through the carburetors and we clearly have not got a stale fuel problem because the front bank of carburetors the inlets are clear but the back bank of carburetors the rearmost bank of six cylinders are actually black inside the carburetors which either means there's something drastically wrong with one of three things the fueling the valve timing or the ignition timing and i'm going to eliminate valve timing because we've not long rebuilt the engine and we know that the valve timing is set up and nobody else has been tinkering with the car so i mean it's a really odd problem this is not what i was expecting so we're going to just check the ignition timing in the fueling the carburetors and see what's going on there well um we put the trumpets on and given it a run and uh quite clearly it's spitting back through these so we could monitor exactly we've also done ignition timing on this bank and it's 21 degrees advanced over what it should be and that is enough actually to give us a problem it sort of throws the combustion process out of kilter and you end up getting uh spitting back back firing which gives a bit of carbon buildup a bit of exhaust essentially coming into the inlet so undoubtedly uh something is not right inside here so i'm going to take this distributor off and strip it down and see what we find well here's the distributor we've taken it off um some mirrors have two six-cylinder distributors because a v12 is two six-cylinder engines and some of them have a one 12-cylinder distributor depending on whether they've got air conditioning fitted or not if they have got air con they need the space of the second distributor to put the air conditioning bracket on so this is a non-air conditioned car so therefore it has a six cylinder distributor we did fit electronic ignition to this car when we restored it quite whizzy um electronic distributors fully electronic but unfortunately one of them has very unusually failed so we put it back on this conventional morelli lamborghini system which is what they had on when they were new and actually they work surprisingly well if they're maintained you've got two sets of contact points in here which make and break and they are synchronized to coincide with the firing order of the six cylinders and then you have the distributor shaft which rotates here but the interesting thing is um and this is this is um i've identified that this is the problem this is called the centrifugal advance mechanism and it relies on weights which as the as this drum spins faster with engine revs the weights actually go outwards again spring pressure and alter the position of this the distributor ignition point as compared to what's happening at this end so this end is turning and that's the weights actually move out under spring pressure what's happened is one of the springs is broken inside which is causing this to move too easily so we checked the ignition timing and it should be 18 degrees before top dead center and it was actually 21 degrees advanced which by my arithmetic equals 39 degrees so that's too much and that's why it was actually spitting back through the carburetors and causing the inside to have combustion dust a little bit of a film of carbon in there so i'm going to put a new spring in here this this is very old technology um this is effectively um taken from a steam engine from the governor on a steam engine that had bob weights on it as they're called which expanded with centrifugal force until they reached a certain point and they stopped the engine over speeding using a linkage very clever steam engine technology these were around for years in various forms because the faster the engine revs the sooner the spark has to happen on a a gasoline or petrol engine because the explosion takes the same length of time effectively even though things around it are happening a lot more more quickly so that's why the spark advance has to happen at higher rpm and it's amazing to think that something as tiny as a broken spring can can cause all these problems something as tiny so i'm going to strip the distributor now strip this off there's that bit which is the plate and then we have the bob weights here which are on pivots they come off and we can clean all this lot up it's not in bad condition actually i'm pretty sure we did something with them at the time as a backup just in case of situations such as this that's actually the good one but the other one is broken and what's happening is it's allowing the weight to spring open too soon so all that affects the running of a 380 brake horsepower engine it can cause it to run out of kilter essentially so um i'll build this up with some new springs and then we'll uh it's all preset um we've checked the the clearances and everything that they're all to factory specs so when i build this back up um with the correct springs it will all function exactly as it should do but it's really amazing it's it's uh very interesting to think that this dates back to uh the 16 or 1700s with steam engine technology uh still using this kind of mechanism today and it works very well these morelli distributors are very reliable actually generally speaking so yeah we found the problem not what i thought it was but every day is a school day well we've got our two new springs here and this has been cleaned out the the housing assembly the drum so i'm just going to build this up with a little bit of copper grease um these are beautifully engineered these uh morelli distributors they are italian precision engineering at their finest probably which is a very sad thing for me to say because the lucas distributors um people called lucas the prince of darkness particularly in america and unfortunately it wasn't on altogether um untrue so put that in there in there a little bit of copper grease um but these uh that they will sort of run a v12 engine um for many thousands of miles if they're set up properly which is very impressive really so we put that in there a little bit of copper grease and we build those up on there these components are in fabulous condition really when you consider this is 50 years old okay i will concede it hasn't done an amazing amount of miles but even so put that on there oh yes that is much much tougher and it's also returning to the rest position that's much better put a little bit of copper grease in there same on that side wipe off the excess and back into the distributor it goes and back on the car as i was saying earlier we've got these contact points here the contact breakers which as this three-lobed cam rotates it's not working properly at the moment because it's not fixed at the top it actually opens the points as the cam comes over and then closes them again and then it synchronizes the other set to open in between so you get you get six openings of the points per revolution of the distributor which is your six cylinders on that bank and as they open they cause the ignition coil to go in to exert a high voltage spark out of the outlet on the distributor which then goes to the spark plug and obviously it combusts the mixture but the interesting thing is we've got to be careful because with quite a lot of modern electronic ignition systems we've actually experienced that if we put too strong a spark on these old ignition systems whether this bit needs to be electronic or not the actual infrastructure the cap and the rotor arm there's the rotor arm that fits on the shaft and revolves they actually get the spark jumping and it causes a misfire in the car so there's a limit to how much the original ignition system can cope with voltage-wise some people would say take it off and put a new ultra high energy all electronic ignition system on get rid of everything but things like that are the question how far do we go how far do we keep it original but anyway this is all built up now until the electronic ignition system comes back we'll put that back on the car and the car should perform beautifully in the meantime should okay let's see well as ever the byword with uh classic cars is warming them up properly so i'm just doing that now but i can tell already that it's very different it's smoother um the response is more linear uh everything's happy for one to a better way of putting it no spitting back uh these mirrors do not get any bigger to sit in they really are tiny and i can't quite understand bob wallace who was the the test driver for lamborghini at the time was six foot two i'm just on six foot and they actually made the miura two inches lower to start with how on earth he fitted in those i have no idea okay he was rather slimmer than me but um incredible uh really even with the extra two inches of roof space there is negligible room inside them i'm sure i'm sure they're getting smaller with everyone i get in but anyway we won't dwell on that but everything's warming through feels lovely and smooth that's uh that's just on 2000 rpm now engine is very happy we might have a bit of a result here following my discovering and authenticating the italian job mura in 2016 i thought that would be the career highlight of my life uh but there's actually another one on the way which i think will beat that so that's a little spoiler i'm going to say no more but we have something very exciting coming up in 2022 but i'm very very happy with this car the way it's going she's still not up to temperature so we're just monitoring that and the other thing to mention is that the engine warm-up video is on the way uh it takes a bit of putting together because i'm using so many different engines as an example but um i did mention a while back about how to start and warm up different types of classic car i am going to be doing that in the near future but we'll just bear with this car a few minutes and just warm it through well things have worn through now one of the joys of this job it's so satisfying when we've um when we've done a complete restoration and the whole car has been torn apart to the very last nut and bolt and put back together again one of the real challenges on miura's is the gearbox as i've said before on videos because the gear change goes literally through the engine to the gearbox at the back it's quite a complicated linkage to to put it mildly and it's very difficult to get them optimal um they are notoriously difficult and this one is really now it's warmed up very happy it's a joy to use actually it's all to do with the thickness of the molybdenum coating on the synchro rings it's quite involved it's quite um technical to get them right um but once they are right or as right as they can be it's never going to be fingertip like a modern um sort of a 1990s or early naughties honda or something like that but it's nevertheless uh very good just click click from three to four and once again the engine because it's set up properly it's quite happy just to tinker along um i'm doing all of uh 70 kilometers an hour at the moment uh just just uh ambling along in fourth gear miura's in the day had a reputation for conking out for being unreliable um just breaking down and the reason one of the reasons for that is that the the carburetors more often than not just weren't tuned properly on them um and they were over rich and the plugs got fouled up and eventually i mean i've heard many stories of film shoots where um the mural has just just given up halfway through uh but uh not this one it's uh oh it wants to go now it's warm i can feel it chomping at the bit it's really really wanting to meet just to open the taps and give it its head so now that everything's warmed up and the carburetors are sorted out and the timing's sorted out let's give it a try that is fantastic all present and correct all six bulls charging all 12 bulls charging wonderful we'll try that again yes that is a result beautifully running all the piston rings bedded into the boards all the valves doing their bit everything's sparking at the right time burning and turning properly great fantastic we don't think about how much it's worth we just think about the open road and the loud pedal um so wow well that concludes another classic workshop video hope you've enjoyed it uh please share please like please subscribe and you can follow me on instagram as well for some sort of quirky snapshots of life in the universe and we'll be back with something else very soon you

Channel: Tyrrell's Classic Workshop

Views: 244,519

Keywords: Iain Tyrrell, Tyrrell's Classic Workshop, Classic Car Expert, Classic Car Restoration, Classic Car Insights, Classic Cars Cheshire, Lamborghini, Miura, Blue Speciale, V12, Rotisserie Ground Up Restoration, Road Testing, Shakedown, Running fault, Carburetors, Inlets, Carbon, Distributor, Centrifugal governor, Windmills, Steam Engines, Christiaan Huygens, James Watt, Engine Tuning

Id: 4Sett24vQ-w

Length: 20min 11sec (1211 seconds)

Published: Sun Feb 06 2022