This is GREAT stuff, been watching your videos about the SU carbs. Learned a LOT from this, and my Volvo B20 is running better than ever a BIG thx for your informative work :-)
Very helpful. I met John around 85 or 86 I think when he restored the carbs on my Dad's '69 B. We drove up to his shop from Chicago to pick them up. The bodies were glass beaded and the bowls polished. They were beautiful. I just picked up a '72 BGT that has been parked for 3 years, so a tune and carb sync is on the horizon.
Very useful video! Just bought a set of twin SU carburettors for our '77 spitfire 1500, maybe now it will be ready to run by spring time, great video .
Thanks, working on a 78 rolls royce with a dual HIF SU setup, after much fiddling using this procedure figured out one is not flowing enough fuel regardless of adjustment but the other works well, so I am taking bad one off to re-check the float level and jet for obstructions.
I used to own an MGB GT back in the 80's, my method of tuning the carbs after making sure all other aspects were OK, ie timing, mixture, etc was to use a piece of rubber tubing and listen to the 'Hiss' on each Venturi. I used to adjust each carb so that the 'Hiss' was equal on both. A bit of a Red Kneck approach but it worked for me.
Two other additions to the balancing of HIF's at idle and fast idle versus at higher speeds: 1) after a long time, the two soft springs pressing against the two pistons may become unequal in length/strength. The mixture at higher throttle then comes out of balance. They come cheap, so in doubt renew...... 2) looking at the color of the spark plugs after a long drive on the highway gives a perfect indication of balance in mixture at higher throttle. A quarter turn left or right is often enough.
Is the "finger" of the plate attached to the throttle shaft supposed to come in contact with the lower choke shaft at zero throttle or idle? Does that act as a stop or limit for the throttle shaft? Can anyone clarify this?
Asking for your help: I’ve got a ‘73 MGB with 2 SU (HIF4) (AUD 550) carbs… At startup, choke-on, underneath the rear Skinner Union are fumes coming off the exhaust pipe- I’m thinking it’s a gas leak from the carb to the hot pipe? But, when the choke is off, no fumes. When running, no fumes. At idle after a drive, no fumes. Can the choke-on at startup cause my SUs to leak? Thank you, Neil Shovlin a Subscriber.
Very informative video. I look forward to using this a little more thoroughly when I am adjusting my SU, I pick up the car tomorrow its a '72 triumph. Whats that tool called with the ball in it? Might have to purchase one for myself to get things accurate. I think I'll be swapping the single SU out for Twin 40's in the spring, but we'll see how she goes first.
I'm guessing all MGs left the factory jetted for sea level. Everyone wants to complain about SU carbs not knowing how to tune them, they actually perform very well.
OH , Btw, Im trying my SU Carb Tuning atm, and i cant get it right, everytime i lift the piston it either just stumbles or rises then stumbles to an almost stall, is the "rises and stumblesto an almost stall" what i should be looking for? because iv always assumed that the engine should go back to its normal idle when lifting the piston
hi john great vids , i just bought a 72 mg mgb it has no brakes and the pedal goes to the floor, and there is no leaks i can see and the fluid stays the same level in the master cylinder can you point me in the right dirrection on the problem? Thanks You in advance
If you're watching this video, definitely also check out this later video, czcams.com/video/4nvGLgO6pj0/video.html. It covers a lot of the same material, but with a higher definition video. The two definitely compliment each other.
I've got myself a weber 32 ibf for my 1.1 mk2 ford fiesta, it did have a ford own design carb, called the Ford VV carb - but it was terrible, so now i've got the weber 32, much much better! I like webers anyway!
Instead of changing parts you will need to do some testing. establish your light works on the car, then use the timing light when it dies to figure out if you have any spark to any cylinders. If you do, then its fuel related. It could be possibly boiling fuel and vaporlocking. Are the carbs hot? The pump maybe pushing, do you have a gauge in line near the carbs to see if the fuel is making it up front? If you do have fuel problem have to check tank vent all that stuff as it may build up vacuum.
Wish the carbbies where SU HS4's, because along with a new Lumignition 123 dizzy, the 1972 carburettors that are fitted to an American import 1970 MG B with I think a 1974 engine (no ID plates fitted, except for South Australian Police plates!!) have been troublesome even a so called SU specialist could not get the engine to run without stalling under load when blue flame was showing on the colortune. The carries nave to be adjusted rich for it to run and of course black plugs and misfires are the result. Oh, well Safety Fast or Stuttering!!
TOOO bad you guys are over seas, My Triumph 2500 TC could use a little work!, I just replaced the clutch only to find it wasnt the release bearing making the noise.. the gearbox is naffed, also, it needs one hellova tune as its been sitting for so long!
These are horrible carbs. Had them on my 240Z and the throttle response was just terrible. I can't imagine who thought to put these on any car including the e type jags. I got rid of them and went to a great carb made by weber. It is a must change out or any car that is stuck with these oversized motorcycle carbs. I think the only reason we see them on cars is cost. If you have them on any car get a weber conversion kit and make the car work right.
I replaced my 260z Hitachi smog carbs with a pair of SU HIF 6 carbs and your videos have been a great help!
This is GREAT stuff, been watching your videos about the SU carbs.
Learned a LOT from this, and my Volvo B20 is running better than ever
a BIG thx for your informative work :-)
Another excellent John Twist Video -- a must for anyone that has an MGB
Very helpful. I met John around 85 or 86 I think when he restored the carbs on my Dad's '69 B. We drove up to his shop from Chicago to pick them up. The bodies were glass beaded and the bowls polished. They were beautiful. I just picked up a '72 BGT that has been parked for 3 years, so a tune and carb sync is on the horizon.
Very useful video! Just bought a set of twin SU carburettors for our '77 spitfire 1500, maybe now it will be ready to run by spring time, great video .
I think my old Volvo likes me more now thanks to You John. Thank You!
Great video and tuning process, very simple. I love my SUs!!!
This was VERY helpful! Thank you very much, John.
Chapeau, very well TUTORIAL!!!
Followed your guide to the letter. Spot on!
John, you are awesome! I wish you were closer, you'd have my business.
Thanks, working on a 78 rolls royce with a dual HIF SU setup, after much fiddling using this procedure figured out one is not flowing enough fuel regardless of adjustment but the other works well, so I am taking bad one off to re-check the float level and jet for obstructions.
Thanks! It was interresting for my 240z su !
Outstanding, Thank you
Barry, MGCCT
Very well explained, like it
Thank you ! Great information.
This video is very educational , thanks!!!
Thanks Man Great Help...
really useful tutorial!....thanks a lot
Very helpful but don't have the tools necessary to do it myself wish were in Ft. Myers Fl. thanks for all your help
Great video
that was very easy vid he says everything in plain english and makes it look so easy gary in the uk
I used to own an MGB GT back in the 80's, my method of tuning the carbs after making sure all other aspects were OK, ie timing, mixture, etc was to use a piece of rubber tubing and listen to the 'Hiss' on each Venturi. I used to adjust each carb so that the 'Hiss' was equal on both. A bit of a Red Kneck approach but it worked for me.
Hola. Podrías explicarme como usabas el tubo de goma. fabio.martinez@hotmail.com.ar. Gracias.
Muy lindo !! Gracias,desde argentina.
This was quite helpful for my '62 AH Sprite. It now purrrrrs.......
Best info as always, to compare to others info
Two other additions to the balancing of HIF's at idle and fast idle versus at higher speeds:
1) after a long time, the two soft springs pressing against the two pistons may become unequal in length/strength. The mixture at higher throttle then comes out of balance. They come cheap, so in doubt renew......
2) looking at the color of the spark plugs after a long drive on the highway gives a perfect indication of balance in mixture at higher throttle. A quarter turn left or right is often enough.
It's also important to make sure that the pistons rise the same amount when you open the throttle
Is the "finger" of the plate attached to the throttle shaft supposed to come in contact with the lower choke shaft at zero throttle or idle? Does that act as a stop or limit for the throttle shaft? Can anyone clarify this?
Asking for your help: I’ve got a ‘73 MGB with 2 SU (HIF4) (AUD 550) carbs… At startup, choke-on, underneath the rear Skinner Union are fumes coming off the exhaust pipe- I’m thinking it’s a gas leak from the carb to the hot pipe? But, when the choke is off, no fumes. When running, no fumes. At idle after a drive, no fumes. Can the choke-on at startup cause my SUs to leak? Thank you, Neil Shovlin a Subscriber.
What if the rpm falls when I put the uni syn on? Also it barely raises the red ball a quarter way up
What does it mean when I put the unisyn on the mouth of teh carb and RPMs rise about 200 RPMs?
Very informative video. I look forward to using this a little more thoroughly when I am adjusting my SU, I pick up the car tomorrow its a '72 triumph. Whats that tool called with the ball in it? Might have to purchase one for myself to get things accurate. I think I'll be swapping the single SU out for Twin 40's in the spring, but we'll see how she goes first.
I'm guessing all MGs left the factory jetted for sea level. Everyone wants to complain about SU carbs not knowing how to tune them, they actually perform very well.
I would like to get one of those balancing gauges. Could you recommend me one please?
this was great content, it would great if it was redone with better cameras.
@Sulaimaa hey im watching this video because I also need to tune the carbs on my 240z. How did it work out for you?
OH , Btw, Im trying my SU Carb Tuning atm, and i cant get it right, everytime i lift the piston it either just stumbles or rises then stumbles to an almost stall, is the "rises and stumblesto an almost stall" what i should be looking for? because iv always assumed that the engine should go back to its normal idle when lifting the piston
What happens if all is good and well and you choke it and one is now pulling more than the other? WHat do you adjust from there?
hi john great vids , i just bought a 72 mg mgb it has no brakes and the pedal goes to the floor, and there is no leaks i can see and the fluid stays the same level in the master cylinder can you point me in the right dirrection on the problem? Thanks You in advance
If you're watching this video, definitely also check out this later video, czcams.com/video/4nvGLgO6pj0/video.html. It covers a lot of the same material, but with a higher definition video. The two definitely compliment each other.
whats that tool hes using to gage airflow?
I've got myself a weber 32 ibf for my 1.1 mk2 ford fiesta, it did have a ford own design carb, called the Ford VV carb - but it was terrible, so now i've got the weber 32, much much better! I like webers anyway!
roughly how many turns out are those mixture screws?
gunsmoke
If all the way rich, does that mean ? An issue with that SU?
Instead of changing parts you will need to do some testing. establish your light works on the car, then use the timing light when it dies to figure out if you have any spark to any cylinders. If you do, then its fuel related. It could be possibly boiling fuel and vaporlocking. Are the carbs hot? The pump maybe pushing, do you have a gauge in line near the carbs to see if the fuel is making it up front? If you do have fuel problem have to check tank vent all that stuff as it may build up vacuum.
hi....I'm converting my fuel injected xj6 jag to triple SUs,,,,,can you let me know iof you source that tool....looks better than the hiss test
Hi I have problems with the carburetor a Daimler 250 of 1966 could help me.
Wot probs you having
My car has a carburettor... Is a carburetter a very different thing?
Wish the carbbies where SU HS4's, because along with a new Lumignition 123 dizzy, the 1972 carburettors that are fitted to an American import 1970 MG B with I think a 1974 engine (no ID plates fitted, except for South Australian Police plates!!) have been troublesome even a so called SU specialist could not get the engine to run without stalling under load when blue flame was showing on the colortune. The carries nave to be adjusted rich for it to run and of course black plugs and misfires are the result. Oh, well Safety Fast or Stuttering!!
I'm about to tackle the triple HS4 set up on my ride... not for the feint hearted...
Spinning like a kitten after a total renovation and several hours of polishing
Wrong needles in it if your mixture screw is all the way down lol
TOOO bad you guys are over seas, My Triumph 2500 TC could use a little work!, I just replaced the clutch only to find it wasnt the release bearing making the noise.. the gearbox is naffed, also, it needs one hellova tune as its been sitting for so long!
Good video shame about the quality
These are horrible carbs. Had them on my 240Z and the throttle response was just terrible. I can't imagine who thought to put these on any car including the e type jags.
I got rid of them and went to a great carb made by weber. It is a must change out or any car that is stuck with these oversized motorcycle carbs.
I think the only reason we see them on cars is cost. If you have them on any car get a weber conversion kit and make the car work right.