342 MG Tech | Fitting and Tuning H Type SU Carburetors on Your MG

John Twist shows how to tune H Type SU Carburetors, mentioning key points to be aware of and the tools you'll need to do it yourself. Thanks for watching and Safety Fast!
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[@mohanperformance.enginerd.1308]

Ahhh. The good old days. I was trained in English su's on Volvo when I was age 15. I have not got to work on a pair for years. KD needles and 30 wt was pretty close on a b20b.

[@truethought369]

Interesting, that you use sound to balance or pear the throttle butterfly's. Thats new to me! When I did that years ago, I put the carbs on the manifold. Then, I put lights behind the manifold, with a blanket over my head, so I could see the cresants of light shining from both slides. I found this was best for me to get it spot on. Mind you, I am a visual learner and my hearing was below par. I remember a common problem with the SUs, which was the Flexi fuel pipe could get blocked due to no inline filter! This was sorted once a filter was fitted. Thanks for your video, have great day 🙂🇬🇧

[@roberthepburn6087]

I have gone thru your video a few times and decided today to do the carbs on my BugEye with 1 1/4" SU's which are different from the video but work the same way. I took my time and stopped the video every time I went to do what you suggested. After I was done Itook the car for a drive and wow...such a difference......great job and thank you for doing this

[@strawz007]

Thank you John, have taken over from my dad a 1967 MGB GT. Very new to tuning old cars. You're video is great👍

[@chrisevans8308]

God i wish I had this mans knowledge on MG’S.

[@ThatChrisSneedon]

Great video!! Glad to see you’re coming to Portland for All British. It’ll be great to meet you!

[@carbostar]

Clear and concise reference for every step of setting up the carb's,

[@johngenova9870]

Comprehensive video, thanks John!

[@airman49]

Hi John, I have watched a lot of your videos and they are very informative. Have had british cars for over 40 years now. Mostly Minis. I have a -69 MGC GT now which I have had for nearly 8 years now and it took some time and experimenting to tune the carbs right. I have always used a rubber tube for syncronizing but used a Colortune for adjusting the mixture. It works fine. But my experience is that the MGC likes to run a litte rich.

[@americanpatriot2422]

Outstanding video and presentation

[@rolfastrom586]

Tuning a Volvo with SU carbs, very helpful video. Thanks for doing this!

[@rogerinbrighton]

Great video!!!

[@can-cruiser]

Great video.. I'm just about to embark on rebuilding a set of H Type for my MGA. Thanks John!

[@netpackrat]

If you haven't already done so, check out some of his earlier videos on the SU carburetors. Lots of good info in there.

[@riderzinc]

Thank you, I’ve got a set of H4’s on my British Ford Zephyr i need to tune, Changing it from filters to open intake stacks so will need to tune it

[@angrybreadbox]

I'd love to see ya come to northern Michigan!!

[@HamishRacing]

Thanks John great video hope I’m allowed on your channel ( I race a TR3a 😳) but my H6’s need a little attention to match them up looking at the plugs. The front 2 are a bit leaner.

[@martinharris5017]

I have a few of these carbs lying around, Putting an HS4 on my VW Beetle!

[@steverabinowitz4216]

Great video. Very Informative. After you synchronized the carbs, you locked the carb linkage back together. Then you adjusted the mixture on the front carb. Once you had that set, you brought the RPM down by adjusting the front throttle screw. In effect, lowering the air flow through both carbs. Then you adjusted the mixture on the back carb and once set, the RPM's increased. You lowered the RPM's by adjusting the rear throttle screw. Wouldn't that effect the front carb? Since the front one was set with the proper mixture and air flow, wouldn't the air flow through the front carb now be too low? Edit: I went back and watched the video and at 7:15 I think you answered my question. You said any adjustment to the throttle screw must also be made in the opposite direction on the other carb throttle screw. Sound right?

[@LegendsWorkshop]

What kind of camera are you using? The picture's fantastic. Thanks!

[@ivanscountrymusicandcars2357]

Are these similar to SU Carbs on the Datsun Roadsters? I have never heard of MG are they collectable? How are they on reliability? Are they known to leak? I have always wanted a Datsun Roadster since I was a kid but if these MG’s are less expensive maybe I will settle.

[@gregnovak0070]

Great video, I wonder if you could talk about matching carb's and manifolds to distributors on an MGB? I have a late model 18V engine and carbs using an early model distributor and notice the vacuum advance takes vacuum from the manifold instead of the carbs. Seems like the advance would occur under different conditions so wonder if the dizzy should be matched? Car runs beautifully as a daily drive, but does seem to use more gas than I would expect and exhaust is a little sooty. Thanks, greg

[@UniversityMotorsOnline]

Good idea for a video! If your plugs are blackened then the carbs are too rich. Turn the jets up three flats / half turn and check the plugs after a five mile run.

[@TinaFollett-es5un]

Hi John, do you have a site I can by su twin carb and manifold to suit a Wolseley 1500.?

[@alextr3a640]

Hi John, great video! Love it! Just one question, if you lift the piston, just a little, so not pushing the pistonpin on the side all the way up, how long do you suppose to lift the piston? Can’t find it anywhere, also not in the original manuals…. Please let me know! Thanks, Alexander

[@UniversityMotorsOnline]

When you lift the piston the vacuum at the jet is reduced which leans out the mixture. You have results immediately when disturbing the piston's height. Move it just "a bit!" You can always call me.

[@alextr3a640]

@@UniversityMotorsOnline Hi John, thanks, so you are telling me; just lift the piston very slightly and for just a moment within a second? :-)

[@NickG24]

Hi John, I’m adjusting carbs on my Mg midget (later style Hs4 but basically the same). This is the bit that’s confusing me, isn’t lifting the piston, the same as dropping the jet, therefore richening the mixture? Instead of the jet falling away from needle, the needle is moving up as it would as the revs increased by sucking the piston upwards?

[@ianwilliams1448]

No wonder I can't get the settings correct.. I'm not dismantling the lever below. I only releasing the spindle !

[@heatheridoni1213]

This is great. I recently rebuilt the carburettors for my MGA. Getting that rear lower bolt on and off the intake manifold was quite a chore (and my children learned some new vocabulary watching me do it). When I was all done, it started beautifully from cold (the "choke" worked properly for the first time since I've owned it), but there seems to be a vacuum leak. I tried spraying carb cleaner to localize it to no avail, and listening with a stethoscope makes me think there is a big leak around the gaskets. Can you please do a basic video on how actually to get them off and on properly?

[@UniversityMotorsOnline]

I'll try! Use GREASE on all the gaskets.

[@scottjohnson7774]

SU dashpot oil is SAE 20. if you need to use 90 weight that carb needs to be replaced

[@tedsmith_photography]

I've been putting 20/50 classic engine oil in my carbs John. Is that not right? You mention to use gear oil? Is that more suitable?

[@UniversityMotorsOnline]

I find 80/90 gear oil to be thicker to account for wear on the dashpots so the acceleration is rich enough. Some engineers say 80/90 is the same as 20/50.

[@NickG24]

The manuals in the later cars tell you to use 20/50. I was quite surprised as I thought dashpot oil would be thin.

[@walterjanssens8485]

I'm revising the carburators for an MG TD 1957 but noticed the 2 springs on the pistons are missing and probably never installed. Are these springs needed when the pistons are brass and thus heavy?

[@35terraplane]

No, springs were fitted after they went to lighter weight pistons

[@garyowen9044]

I’d need a full rich Ritalin drip 💧.

[@daveman1975]

Best way to tune those is to throw em in the trash.