You have said the most important thing, namely that you can't tell by ear whether fuelling is correct. It requires measurement and adjustment of needle profile, ideally on a carb that isn't worn out. Unfortunately there are people happy to take money off owners for twiddling the mixture screw. They probably don't have a gas analyser, saying Oh I'm so experienced, I do it by ear.
Great explanation a a black art AC. I’m fascinated by all this as I have a 1380 with HIF44 track day car. My neighbours despair at my revving after carb and distributor rebuilds and setups. I have learnt so much from your videos and can’t thank you enough for sharing your expertise.
I've been watching all your tuning videos for the last few years, and since swapping to a single HIF44 (after using a Dellorto DHLA40 and twin HS2) and following your advice mine is running superbly. I had an O2 sensor bung installed and I managed to get the 0.95 lambda the whole way up the RPM range at part throttle. It gets a bit rich at low RPM when accelerating so I think the damper will need to be swapped to the 2085. Overall it's been running so well I took out the AFR gauge as I was so happy with it. Going from a 3 ohm coil to a 12V 1.5 ohm (with variable dwell) gave me the extra spark power for "lean" cruising and no more misfiring, lean spots or fouled plugs All of what I've done is contrary to a the "old-fashioned 1960's thinking" of mini tuning that most people do here
There you go, you have experience it for yourself, calibration is key and you will Also notice that very few others have their carburetters set anywhere near close to Being correct.
thanks AC. Your vids have much improved my spark and fuelling knowledge. I conclude amateurs like me will not be able to get fuelling right without an exhaust gas analyzer, which I do not currently have. John in Manitoba.
@@ACDodd When I trained to be a mechanic in the late eighties, carbs were of course common. I’ve been in an office for 16 years, and becoming nostalgic and want to get back to “the roots”, I’ve just bought a Mini in which the engine is being rebuilt. It’s a 1275 with a S cylinder head, Kent 264/268 and 1.5 roller rockers. It has twin SU HS2, so I’m a bit concerned how the fuelling will be. So your videos are gold! I didn’t know anything about setting up SU’s, but now I at least know something😀
Two questions,if I may. You drew the graph with nominal lines for bore wash and misfire zone. What actual figures do you place on those lines? Secondly, do you check the fuelling under load, rather than free revving? I dabbled with SU carbs for some years, and replaced a Weber 34ICH with an ISO 38mm (SU clone, better engineered in my opinion) and after a short time realised that the jet was .095”, rather than .090” or .100” so none of the SU needles were of any use and engine ran very weak once off idle. I then realised I had to fine tune my own needle. After I’d got it running as well as I could I took the car to a professional, who tunes many classic cars for racing as well as road use, for rolling road work. After a couple of runs he laughed and took the plugs out to show me the colour. He said there was nothing much he could do to improve the mixture because I’d got it spot on across the full range. He did manage to get a little more power by adjusting the timing. He jokingly asked me if I wanted a job and we became good friends. I’ve since moved on to fuel injection and built my own fuel injection system. Rather than modifying needles and distributors I now enjoy tuning with my laptop. All fascinating stuff. I still used my Colortune transparent spark plug to get the car running well enough to begin with and my Gunsons Gastester to further improve it before I began actual road work.
Can’t quote actual figure for the misfire limit You have to measure that as it depends on cylinder pressure, spark Power, fuel type engine speed etc. bore wash actually starts happening from the point you have more fuel than stoic. Hence the need to run engines at sensible settings when the engine is being driven most of the time cruising and par throttle. Full power fueling causes more wear, but as the engine is only of full power for minimal periods in a road engine it’s not a concern. After dyno testing many su equipped engines I can tell you that setting the part throttle fueling using the method shown here shows little to no difference. In order to properly dial in full power fueling a load is required.
@@ACDodd Thanks, much as I thought. 🫡 The software for my ECU has fifteen load positions (I fitted a throttle position sensor to indicate load). I’ve spent a great deal of time getting the drivability correct, loading the engine up by various methods. As a trials car it needs to pull reliably from idle right up to full power and it now does so. I’ve also built a device to listen for knock on the road to get the best out of the engine when building the timing curve. My professional engine tuner tried it and said it’s as good as his own device which cost many times more than mine did.
@ Especially if you’re doing stuff on a very low budget. Had a bad experience or three with another so-called professional tuner who at times seemed to know less than I did. I eventually decided I’d have a go myself rather than keep throwing money away on his efforts.
Thanks AC, enjoyed the deep dive. Glad my Metro's carb wasn't as worn as the example here!🫣 Amazing that a 'tuner' left the Mini unable to teach 5k revs and thought 'good job'! 🙄😡 Glad you were able to get the engine running much, much better. Cheers Steve
Out of interest (as a non SU carb owner), typically what mileage should a decently tuned A series engine do before the engine needs a rebuild and the carbs become worn? I guess this is a 'how long is a piece of string' question - but given that most A series owners now are enthusiasts, how often will a car with a properly built road tune need checking. As a Ford bloke from the 80's we were always tinkering, but what are the signs that stuff has worn. Big question i know because we have to include the dizzy wear! My MIL has a mini 1000 auto... Also - in your honest opinion and given your knowledge, were many main dealer garages were equipped with the deep knowledge and training to get the best out of these lovely cars even when new? Most modern engines will smash past 150K miles but my 10 year old Escort Mk1 1300 was very tired at 70K miles. Do modem machining methods give old engines a longer life? What's Changed? Most of my early cars went to the scrappy because of rust - everything else was easy to get to on a weekend. Given that you can beat the tin worm these days, is a classic mini an viable daily drive without a garage? Asking for a wife with a love of minis (and no garage because that is where my motorcycles live)... Could be an episode there to detail what has changed in the last 30 years.
No, main dealers did not have this skill set. Either biggest effect on engine life is how it’s driven, and how well it’s looked after. They won’t last as long as a modern engine though.
Great video! So the needle fitted was too thick right across the rev range? Making it lean? I’ve a tahini too, mines a 1275 hif38 and has an AEM needle fitted which I believe is what was fitted when new…not that that means anything 30 years later. What do you mean when you say the carb is worn? play in the spindles? Worn throttle disc? Thanks 👍
Worn, wear in every part contributing to a lack of control on the fuel. If a carb cannot adequately control the fueling at all times it needs overhaul.
Thanks AC Loving all the videos. Ive learnt so much. Do you think a gunson exhaust gas analyser or equivelent be enough for a hobbiest to get stuck in with? im keen to learn how to sort the fuelling on my mini especially when i start running in a new engine. Cheers again.
Hi AC. Greetings from Germany. I Tried to follow up your Explantations but because of my english i missed the Point where you mentioned what the figures on the left machine means. Is ist the CO ? Because i have an Innocenti with 2x HS2 carbs i would like to check and see how it is working on different rpm. Greetings Markus
@ Hi….does that mean that if i would find a garage who can measure Lambda at 1000/2000/3000/4000….rpm i exactly know at what rpm My needle need a bit of correction…..? By the way. My car did Not start very Well. I thought it is the battery or the starter, because it was very „Slow“ . Later i realised that it was the cable (negativ/Earth) from the motor to the Frame/Body. What i would like to say/express is, that there are sooooo many things you have to take in considerartion while you trying to sort problems…..
Run E5 and use a fuel stabiliser. Having the carb(s) rebuilt with genuine parts Mean that the carb is fitted with all the ethanol protection that can be afforded. Stabiliser added to your fuel will add the rest of protection needed. At this point there will be no issues with using modern fuels with your SU equipped vehicle. One last point, you need to ensure that all your rubber fuel hose is changed to the correct ethanol rated standard to avoid premature failure of hoses.
@@damiendoran9739then it really important to run a stabiliser, it’s the future and there is no avoiding it. The good news is, your engine will run better anyway!
AC, can I take this opportunity to butt-in and catch your attention to ask what you would recommend as the best non-vac distributor for a MK2 Cooper S 1310 (standard other than hard valve seats and with a negative earth) with rebuilt carbs. Got as far as Powerspark 23D4 electronic but they don't seem to do a High Energy version OR perhaps the CSI distributor with Cooper S advance curve selected would be better - but three times the price?
I would not recommend any non vac dizzy for a road going S engjne, you are better off all round running a vacuum unit unless you have a full race engine build.
@@ACDodd Thanks for your reply and all your videos. So would you recommend using a Powerspark 25D High Energy (using a carb spacer with a vac take-off nozzle)?
@@ACDoddI recommend ported vacuum. I did it successfully after watching your videos. If I could attempt to demystify the process, It ensures that vacuum advance doesn’t begin until you open the butterfly valve. So advance at idle (with throttle closed) is purely centrifugal via distributor. Without this Carburettor mod, there is some vacuum advance added to the static advance at idle so idle advance is too great. You set the static advance at idle with the vacuum pipe disconnected then when you connect it, the advance at idle increases due to a bit of vacuum advance. This is due to the position of the vacuum port on the engine side of the butterfly valve. The mod relocates the vacuum port behind the butterfly valve so you only start getting suction on the vacuum advance when you open the throttle. My engine idles much more smoothly now. I’m surprised that SU didn’t do this originally. I understand there’s a special AC Dodd SU design being manufactured by Berlen Fuel Systems which is a powerful endorsement of the principle. Well done AC.
Another good video. I've learned more about from AC about SUs in the last 10 months than in 40 years in the motor trade!
Wow!
You have said the most important thing, namely that you can't tell by ear whether fuelling is correct. It requires measurement and adjustment of needle profile, ideally on a carb that isn't worn out. Unfortunately there are people happy to take money off owners for twiddling the mixture screw. They probably don't have a gas analyser, saying Oh I'm so experienced, I do it by ear.
thanks for doing this Deep Dive. It clearly shows the value of getting a proper tune!
Really good..........every Mini owner should watch your videos 👍🚘👍
Please share
Great explanation a a black art AC. I’m fascinated by all this as I have a 1380 with HIF44 track day car. My neighbours despair at my revving after carb and distributor rebuilds and setups. I have learnt so much from your videos and can’t thank you enough for sharing your expertise.
I've been watching all your tuning videos for the last few years, and since swapping to a single HIF44 (after using a Dellorto DHLA40 and twin HS2) and following your advice mine is running superbly. I had an O2 sensor bung installed and I managed to get the 0.95 lambda the whole way up the RPM range at part throttle. It gets a bit rich at low RPM when accelerating so I think the damper will need to be swapped to the 2085. Overall it's been running so well I took out the AFR gauge as I was so happy with it.
Going from a 3 ohm coil to a 12V 1.5 ohm (with variable dwell) gave me the extra spark power for "lean" cruising and no more misfiring, lean spots or fouled plugs
All of what I've done is contrary to a the "old-fashioned 1960's thinking" of mini tuning that most people do here
There you go, you have experience it for yourself, calibration is key and you will
Also notice that very few others have their carburetters set anywhere near close to
Being correct.
thanks AC. Your vids have much improved my spark and fuelling knowledge. I conclude amateurs like me will not be able to get fuelling right without an exhaust gas analyzer, which I do not currently have. John in Manitoba.
Peopl think they can do it, but the reality is you do need some training and the right tools.
Another great video. I will definitely be giving you a call when I get my Magnette back up and running.
Friday treat. Cheers AC, another beauty.
Thank you that you give us some background knowledge.
I like these kind of videos
👍👍👍
Great insights, thanks 👍
Thanks for watching!
@@ACDodd When I trained to be a mechanic in the late eighties, carbs were of course common. I’ve been in an office for 16 years, and becoming nostalgic and want to get back to “the roots”, I’ve just bought a Mini in which the engine is being rebuilt. It’s a 1275 with a S cylinder head, Kent 264/268 and 1.5 roller rockers. It has twin SU HS2, so I’m a bit concerned how the fuelling will be. So your videos are gold! I didn’t know anything about setting up SU’s, but now I at least know something😀
Love the info
Perfect video, very informative. Thank you! One question, that misfire limit for high power ignition, could you share around what lambda value it is?
No because it’s different for every engine.
Superb video AC 👌🏼
Glad you like it!
watching this video has made me understand the fuelling on my hif44 better for my 1380 thank you for sharing AC
Glad I could help
Another great Deep Dive and reveal of some information for a correctly tuned SU engine. Great stuff
Two questions,if I may. You drew the graph with nominal lines for bore wash and misfire zone. What actual figures do you place on those lines? Secondly, do you check the fuelling under load, rather than free revving? I dabbled with SU carbs for some years, and replaced a Weber 34ICH with an ISO 38mm (SU clone, better engineered in my opinion) and after a short time realised that the jet was .095”, rather than .090” or .100” so none of the SU needles were of any use and engine ran very weak once off idle. I then realised I had to fine tune my own needle. After I’d got it running as well as I could I took the car to a professional, who tunes many classic cars for racing as well as road use, for rolling road work. After a couple of runs he laughed and took the plugs out to show me the colour. He said there was nothing much he could do to improve the mixture because I’d got it spot on across the full range. He did manage to get a little more power by adjusting the timing. He jokingly asked me if I wanted a job and we became good friends. I’ve since moved on to fuel injection and built my own fuel injection system. Rather than modifying needles and distributors I now enjoy tuning with my laptop. All fascinating stuff. I still used my Colortune transparent spark plug to get the car running well enough to begin with and my Gunsons Gastester to further improve it before I began actual road work.
Can’t quote actual figure for the misfire limit You have to measure that as it depends on cylinder pressure, spark
Power, fuel type engine speed etc. bore wash actually starts happening from the point you have more fuel than stoic. Hence the need to run engines at sensible settings when the engine is being driven most of the time cruising and par throttle. Full power fueling causes more wear, but as the engine is only of full power for minimal periods in a road engine it’s not a concern.
After dyno testing many su equipped engines I can tell you that setting the part throttle fueling using the method shown here shows little to no difference. In order to properly dial in full power fueling a load is required.
@@ACDodd Thanks, much as I thought. 🫡 The software for my ECU has fifteen load positions (I fitted a throttle position sensor to indicate load). I’ve spent a great deal of time getting the drivability correct, loading the engine up by various methods. As a trials car it needs to pull reliably from idle right up to full power and it now does so. I’ve also built a device to listen for knock on the road to get the best out of the engine when building the timing curve. My professional engine tuner tried it and said it’s as good as his own device which cost many times more than mine did.
@@wheater5it’s surprising what you can achieve if you have the time and understanding to.
@ Especially if you’re doing stuff on a very low budget. Had a bad experience or three with another so-called professional tuner who at times seemed to know less than I did. I eventually decided I’d have a go myself rather than keep throwing money away on his efforts.
@@wheater5there are a lot of those still out there!
Thanks AC, enjoyed the deep dive. Glad my Metro's carb wasn't as worn as the example here!🫣 Amazing that a 'tuner' left the Mini unable to teach 5k revs and thought 'good job'! 🙄😡 Glad you were able to get the engine running much, much better. Cheers Steve
As I have said choose your tuner wisely, about a third of my customers have this very experience
@@ACDodd I'm VERY happy with my choice of tuner!!😁🤩👏🙌
Out of interest (as a non SU carb owner), typically what mileage should a decently tuned A series engine do before the engine needs a rebuild and the carbs become worn? I guess this is a 'how long is a piece of string' question - but given that most A series owners now are enthusiasts, how often will a car with a properly built road tune need checking. As a Ford bloke from the 80's we were always tinkering, but what are the signs that stuff has worn. Big question i know because we have to include the dizzy wear! My MIL has a mini 1000 auto...
Also - in your honest opinion and given your knowledge, were many main dealer garages were equipped with the deep knowledge and training to get the best out of these lovely cars even when new? Most modern engines will smash past 150K miles but my 10 year old Escort Mk1 1300 was very tired at 70K miles. Do modem machining methods give old engines a longer life? What's Changed? Most of my early cars went to the scrappy because of rust - everything else was easy to get to on a weekend. Given that you can beat the tin worm these days, is a classic mini an viable daily drive without a garage? Asking for a wife with a love of minis (and no garage because that is where my motorcycles live)... Could be an episode there to detail what has changed in the last 30 years.
No, main dealers did not have this skill set. Either biggest effect on engine life is how it’s driven, and how well it’s looked after. They won’t last as long as a modern engine though.
Great video! So the needle fitted was too thick right across the rev range? Making it lean?
I’ve a tahini too, mines a 1275 hif38 and has an AEM needle fitted which I believe is what was fitted when new…not that that means anything 30 years later.
What do you mean when you say the carb is worn? play in the spindles? Worn throttle disc?
Thanks 👍
Worn, wear in every part contributing to a lack of control on the fuel. If a carb cannot adequately control the fueling at all times it needs overhaul.
Thanks AC Loving all the videos. Ive learnt so much.
Do you think a gunson exhaust gas analyser or equivelent be enough for a hobbiest to get stuck in with?
im keen to learn how to sort the fuelling on my mini especially when i start running in a new engine.
Cheers again.
I think you will be better off with a wideband gauge.
Hi AC. Greetings from Germany. I Tried to follow up your Explantations but because of my english i missed the Point where you mentioned what the figures on the left machine means. Is ist the CO ? Because i have an Innocenti with 2x HS2 carbs i would like to check and see how it is working on different rpm. Greetings Markus
No it’s lambda.
@ Hi….does that mean that if i would find a garage who can measure Lambda at 1000/2000/3000/4000….rpm i exactly know at what rpm My needle need a bit of correction…..?
By the way. My car did Not start very Well. I thought it is the battery or the starter, because it was very „Slow“ . Later i realised that it was the cable (negativ/Earth) from the motor to the Frame/Body. What i would like to say/express is, that there are sooooo many things you have to take in considerartion while you trying to sort problems…..
@@markusstruwe7608yes they can measure the readings, the difficult bit is working out where that is on the needle.
Hi AC I have a question about my 1974 MGB. Would there be any advantage in my replacing the hif44 throttle plates with non overrun type? Please.
This modification may cause it to run rich on overrun.
AC, what are your thoughts on the effects/risks of running E10 with SUs
Run E5 and use a fuel stabiliser. Having the carb(s) rebuilt with genuine parts
Mean that the carb is fitted with all the ethanol protection that can be afforded. Stabiliser added to your fuel will add the rest of protection needed. At this point there will be no issues with using modern fuels with your SU equipped vehicle. One last point, you need to ensure that all your rubber fuel hose is changed to the correct ethanol rated standard to avoid premature failure of hoses.
@ACDodd thanks AC. Unfortunately they have stopped supplying E5 in Ireland so we are forced to run E10
@@damiendoran9739then it really important to run a stabiliser, it’s the future and there is no avoiding it. The good news is, your engine will run better anyway!
Hi would you be interested in tuning my Land Rover v8 the carbs are new on it. Regards Mike.
Yes I can do that. There is a video earlier this year on me tuning a landrover v8
AC, can I take this opportunity to butt-in and catch your attention to ask what you would recommend as the best non-vac distributor for a MK2 Cooper S 1310 (standard other than hard valve seats and with a negative earth) with rebuilt carbs. Got as far as Powerspark 23D4 electronic but they don't seem to do a High Energy version OR perhaps the CSI distributor with Cooper S advance curve selected would be better - but three times the price?
I would not recommend any non vac dizzy for a road going S engjne, you are better off all round running a vacuum unit unless you have a full race engine build.
@@ACDodd Thanks for your reply and all your videos. So would you recommend using a Powerspark 25D High Energy (using a carb spacer with a vac take-off nozzle)?
@@jobrown1485I would convert the carb to ported vacuum and for a re curved 45d dizzy
@@ACDoddI recommend ported vacuum. I did it successfully after watching your videos. If I could attempt to demystify the process, It ensures that vacuum advance doesn’t begin until you open the butterfly valve. So advance at idle (with throttle closed) is purely centrifugal via distributor. Without this Carburettor mod, there is some vacuum advance added to the static advance at idle so idle advance is too great. You set the static advance at idle with the vacuum pipe disconnected then when you connect it, the advance at idle increases due to a bit of vacuum advance. This is due to the position of the vacuum port on the engine side of the butterfly valve. The mod relocates the vacuum port behind the butterfly valve so you only start getting suction on the vacuum advance when you open the throttle. My engine idles much more smoothly now. I’m surprised that SU didn’t do this originally. I understand there’s a special AC Dodd SU design being manufactured by Berlen Fuel Systems which is a powerful endorsement of the principle. Well done AC.
Thank you both for your advice and the information. I will look further into this.