Making the Metro Run Properly - SU Carburettor Needle
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- čas přidán 10. 11. 2023
- Following its gearbox rebuild and modifications, my A-Series-powered Austin Metro doesn't quite run right, so to compensate, we're going to fit its HIF44 SU carburettor with a new needle.
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After 40 plus years of automotive service I can say SU carburetors were my favorite. The simplest to understand and probably the most forgiving. They obviously were designed by someone that understands variables in demand.
So true best carb on the market, in my mind.
Not the best for absolute power, but for road use, you have a point.@@johngrubb1590
I love the old SU carbs. IMO the best carb design ever. They were wear and dirt tolerant and didnt suffer from the piddly drillings and pilot jets of other carbs used by Ford etc. Strombergs were a take on a similar design but the diaphragms were a weak point on those.
Yeah... it's a real head scratcher why the Rube Goldburg of carburetors didn't catch on.
good old Strombergs, heavy black smoke out the back and running rough = split diaphragm
I would strongly recommend you do the tune-up and timing yourself. It's a pretty simple process, and helps hone a suite of intangible automotive senses that are invaluable when it comes to classics. Though it can be a bit of a curse, as you soon realize that many, many "well sorted" classic cars aren't actually running properly!
With a cheap strobe light and some white nail varnish these engines are easy to tune, and using your ear and an su carb adjuster you can set the carb to perfection. the carb can be helped with a slightly stronger spring.
I agree with the other commenters, the SU carb is a lovely device. Deceptively simple but really quite clever. The damper means you don't need an accelerator pump. You floor the throttle and the damper stops the needle flying up but the increased air flow through the throat sucks though more fuel enrichening the mixture until the piston rises again to the 'correct' position. You do have to be careful though that over the years the parts can be interchanged but they aren't always compatible. So you can get the wrong pistons in the wrong dashpots on the wrong bodies. You could definitely rebuild that yourself, it's not too hard and well worth learning how to do it.
Your beguiling smile and giggle that so perfectly reflects your huge pleasure and the satisfaction that you have part-sorted the Metro on its way to perfection. As to tuning, in the distance past, having had rolling road tuning done on my much missed Browns Lane beauty it was a Home Tuning bloke that got it perfect and increased the BHP.
Thanks for morning lift by your enthusiasm.
Rob
Fascinating engineering those carbs. I have a fairly high end British audio system. And when you first started the engine after working on the carb, I thought, "Hmmmm....sounds pretty good! Nice and smooth." Always amazing doing something like that and it turns out so well. Was fun watching something like this being rejuvenated.
Definitely a car guy. We have a habit of fighting with things rather than taking parts out of the way for easy access 😅
I had a 1972 mini that was brilliant. I put a long centre branch exhaust, new 1 3/4" SU carb with a new nweedle and spring. It also had Spax adjustable dampers. One most fun car I have had. It would spin its wheels in 2nd gear with a heavy right foot. I also fitted a smaller steering wheel and a pair of bucket seats. The steering was so direct I just had to think of steering and it would turn. Beautiful. I now own a Ford Focus Vignale estate with 183 BHP three pot engine and while it;s great to drive and fast it's not as entertaing as my mini. Keep up the great videos, well done🙃🙃
I did exactly the same with my 1976 mini. Removed the centre box straight through pipe with straight back box . The good old days no computers then . Couldn't afford disc brakes or servo so adjusting the drums every weekend 🤣🤣🤣🤣👴
Good start Ed. When you rebuild the carb properly, check you have the correct spring too. It controls the speed that the piston moves relative to the vacumn in the carb. It can make a huge difference to the running of the engine.
Ah...... The SU carb. Years back I had a Jag with three of them.
Glad to see your cars have found a good home. Keep up the good work.....
Well done! I thoroughly enjoy watching your progress and your positive attitude.
Cleaning the carb out is easy. Just get a spray can of carburettor cleaner and the muck and staining will just flush away like magic with zero effort. The reason you have brass nuts (and therefore a relatively low torque setting) on the manifold is because the heat would cause a steel nut to corrode onto the studs, making removal almost impossible; nevertheless, it's a good idea to put a dab of Copperslip on the threads to make later removal easy. I have a 948cc Frogeye and a previous owner has removed the original H1 SUs and fitted HS2s; whoever selected the needle spec (they're not the "correct" ones) was a genius because it drives as well as a modern fuel injected car with zero flat spots and zero hesitations and I get 45mpg overall. Granted, I have the knowledge and equipment to balance the pair and set the jet heights perfectly, but I'm still impressed.
I have a 1987 D reg 1300 automatic metro with the same HIF44 carb on it, only 15000 miles on it and amazingly the previous owner had it waxoyled and then stored for years. What I have noticed in almost all metros is that there's a vacuum loss on the crankcase vent system, it gives lumpy idle and flat spots. Simple cure is to unplug the plastic y-piece splitter for the crankcase vent hoses and plug the one coming out of the carb. If it then runs perfectly just stick a small mesh filter on the crankcase vent hoses and let it vent. The other one to watch is a worn throttle spindle which allows a leak but I doubt thats the case unless it gets high mileage perhaps.
Agree with you there Andrew, that breather pipe at the base of the dashpot puts air into the mixture flow just at the wrong point, on my reliants with HS2 carbs I had the same so I plugged the breather port and moved the engine breather pipe to the top face of the K&N so the engine still took in any oil mist and it also could lube the dashpot piston, also i'd still check the throttle spindle for wear SU Burlen do a bush kit for the spindle and also a new spindle should be fitted.
I found by lots of experiments that SUs had a more stable mixture if the spring tension was increased slightly. This was due to changes in the fuel from leaded etc. Modern fuels do not atomize properly in carburetors and increasing the spring tension gives a faster flow accross the needle seat hence a more reliable mixture . I just streatched the springs so they were about an inch higher. However only do this if you have a spare spring to play with. At least with an SU its possible to get them to run perfectly with modern fuels unlike many other carburetors that never work properly.
All you are doing is increasing the accelerator pump effect with the stronger spring. The cruise mixture will still be way off.
@@timbo19751975 in the cases I was thinking about we had perfectly running cars and when the fuel changed (in New Zealand) these cars all ran badly. Increasing spring pressures solved the problem I thought the daspot gave you accelerator pump aciton? A stronger spring will decrease airflow slightly.
Have a go at tuning it yourself. I learned on my mgb and it’s really not that bad. If you mess it up it generally doesn’t hurt and you can get a professional to sort it out later. It takes a few tries at it before your good.
Ed one thing I suggest you try as soon you can rather than change the spring tension is to replace the grade of oil that you have in the dash pot,I would recommend that you change from engine oil to atf automatic transmission fluid which is of a lighter grade and in doing so you will have an easier rate of rise on the piston which will counteract the flat spot when pulling from lower revs in top gear,also a quarter of a turn inwards on the mixture screw will help .
Good luck feel free to give me a shout if you need anything by way of advice.
@Cupid stunt.
Be that as it may ,I've been tuning these for over Fourty years so my Experience tells me that ATF works far better than the recommended grade ,that information you so kindly posted was based on the original design of SU carburettor fitted to the A series engine which first appeared around the time of the Austin A30/35 ,so what was good then is not so suitable for today's version,in conjunction,with higher compression ratios and unleaded fuels these later SUs need all the help they can get,which is the reason behind me offering the benefit of my professional experience to Ed in the first place
So in future if you wish to join the party, bring something useful to the discussion rather than letting what the book says trip off your keyboard on to the page Thankyou.
@@mrcogginsgarage7062 SAE20 is the perfect stuff imho, the original metro manual states 10w/40 for the dashpot along with the engine though I actually put motul 5000 10w/40 motorbike oil in the automatic (engine not dashpot)...again thats something thats turned up as later better knowledge I guess. When you think about it, the auto a-series are similar to wet clutch bikes.
When you think about it the original listed grade of engine /gearbox oil for the A series engine with gearbox in the sump be it automatic or manual transmission was 20/W50 it's what that blend was invented for,
@@mrcogginsgarage7062 Yep the grades changed as the years went on, in 1987 the grade for the 1300 auto was 10w/40, JASO/MA2 to be specific on the auto version, plain 10w/40 on the manual.
You are doing great. Went down many of the same paths as I learned how to tune my Mini's A+ over the last 5 years. It takes some hands on time to understand what helps and what hurts.
If I was doing this carb work I would definitely have had a can of spray carb cleaner available so I could clean the parts of the carburetor before I reassembled it back on the car.
I have an 1989 mini sky, you saw it at Mawdesley earlier this year. It needs tuning, when yours it done could do with mine doing also. Great work Ed.
Thank you for another interesting video.....I always enjoy them. Roger... Pembrokeshire
Thanks as always Roger 🙂
Nice job Ed. Why don't you try tuning it yourself? Can't be that hard? Also would be nice to fit an aftermarket rev counter on the dash, like a Smart car has. Also old skool 😃
Good job, keep it up,
Love watching this channel as it grows. Review my MCS !!
Good to see the Metro coming together. A quick suggestion. It may just be my imagination, but I've always found shallow, flat air filters don't seem to work very well. They make the engine feel a bit strangled to me. A deeper one (I appreciate you have limited space between carb and firewall) might be beneficial.
Awesome work TC…will you run her on the dyno after tuning her?
nice one Ed.
I loved SU carburettors back in the day. simple reliable and very efficient. once you know the basics they're dead easy to maintain and set up. biggest issue used to be float valves leaking and floats going porous. best thing about them was adjusting the jet height to tune out low level mods like putting on a K&N and messing around with different oil viscosities/quantities in the dash pot to change acceleration characteristics. needles and jets only got replaced when really old/worn (jets go egg-shaped) or with slightly more serious engine mods so I'm guessing your later SU doesn't have height adjustment thanks to emission rules maybe???
(best not mention about my mates MGB we stuck a stage 2 cam, double valve springs, K&Ns, a Janspeed exhaust system & a pair of SUs out of a Jag ported to the standard manifold to feed it lol)
back in the day I used to complain about how little space there was in the engine bay. compared to modern cars, there's acres in there.
Fantastic little cars…good work. How’s the BMW going…you never mention it. Great videos…thank you😃👍
Enjoying your videos . do you know the difference between the later A + series engine in the metro and the early 1970's A series engine of same cc ? thanks
Thanks for another interesting vid Edd, my Dad ran Reliants for years and they all were equipped with an SU carb, good reliable carbs, he had very little trouble with them as far as I can remember.
Is that Metro running points ignition or electronic?
I had an E30 like that. The shocks were completely worn so it just oscillated up and down on the springs while driving. Hilarious and awful at the same time.
The carburetors are so different between US and UK cars.
This is a variable-jet carburettor, and some US cars used units that operate on the same principle. The one I'm aware of is the Ford VV carburettor which works like this SU, but turned 90 degrees on its side. However the Ford VV is also regarded as unreliable junk so they've probably all been replaced with fixed-jet units by now.
Ed - youtube AC Dodd.
I have the same problem with my MG B. It runs way too rich. 😢
Put the factory manifold back on.
Aftermarket ‘performance’ ones lose you all you torque. You may (probably won’t) gain a small amount of Hp at the very top of the revs.
Totally not worth it.
Good to see you getting your hands dirty!
I start by opening the jet 3 1/2 turns as a start and then use a gunson colourtune. I hope thats correct?
You do not have the correct original air filter fitted, this could have been the root cause of your carburation problems.