MGB GT - Weber 45 DCOE Idle Tuning

[@badmonkeyspilljuice]

Whoo! The MG is back! Taking mine to the local MG specialist over the weekend to sort out my cold starts and over reliance on Easy Start.

[@peterpowder8546]

Weber is always better!! HOWEVER…… it must be properly tuned using correct jets pumps venturis…. Took me over a year to get my triple Weber setup right on my hotted tr6 but it ultimately ran like fuel injection! Wonderful!! plan on buying a whole lot of parts and spending a whole lot of time what the result is a rewarding new understanding of how these carburetors work

[@louisgrillo9218]

I have SU carbs on my "A", but neat to see how the Colortune works! Thanks.

[@oaktree3278]

Great to see your lovely MG again Mark. Good handy tool that, might try it on the Capri, thanks 😊

[@138Tuber]

Excellent Mark, thank you so much for this video. Very best.

[@SteveDentonClassics]

I see your running NGK spark plugs, bin them!! They cause nothing but misfires and issues, I've had so much experience over the years with NGK spark plugs causing all sorts of issues with British made classic cars and motorbikes, I avoid them like the plague. A good set of Champion N9YC and she'll run so much better, that's what they we're built to run on. Great video mate, them colortunes are a nice little investment for a good basic tune up 👍

[@granblogismo]

Thanks Steve, great advice as ever, ordered some new ones!!

[@stevo6900]

Maybe a few years ago Steve but I personally prefer Japanese to Chinese spark plugs champion are awful plugs now never had a problem with NGK plugs

[@SteveDentonClassics]

Maybe you have had a better experience with NGK than I have, but at the garage I work at for a living, we are endless replacing NGK plugs for other bands as NGK plug electrode tend to fall to bits. A few years back in my Triumph club we did an experiment with 4 TR6s using NGK and Champion plugs. NGK just kept failing, causing misfires etc, Champion never went wrong. I tried a set of NGK in an MGB 2 years back in an attempt to redeem them, nothing but hopeless misfires, replaced with Champion, ran a dream. I tried another set in my own 1965 Triumph Tiger T90 last year, let me tell you having a misfire on a motorbike, and being in the middle of nowhere is no fun. With NGK plugs in it was hard to start and run with a intermittent misfire, I changed them for Champion it starts up first time and runs a dream. I know there is a lot of talk one way or the other with NGK vs Champion plugs. Its much like how some people will only like MG or Triumph, if you've had better luck with NGK that great, but personally I wouldn't stick an NGK spark plug in a lawn mower

[@stevo6900]

Steve you know what it's like with Chinese parts especially classic cars they last five minutes I personally wouldn't use champion in a car but brought several sets for my gardening equipment one plug didn't run the other didn't last a day I know they were a good British company used nothing but champion back in the 70-80s unfortunately long gone now Japanese is probably best Denso or NGK even Bosch are going down hill now

[@SteveDentonClassics]

I know what you mean, it's something that'll we'll probably never agree on, so may as well leave it their. The thing is you get good batches of things, and bad batches of things. You've had good luck with NGK, I've had bad luck. I've had good luck with Champion, you've had bad luck. I'll never doubt Denso and Bosch are very good, but I won't use NGK, as much as you won't use Champion. As I said it's like MG and Triumph, some things people will never agree on

[@andrewb3497]

As hinted in the RedlineWeber article it is the position of the butterfly throttle plates with respect to the progression holes that is important for correct idle setup. On the Weber45 152G model the edge of the plate(s) should just cover the first progression hole however on some of the earlier Spanish Webers that only have 3 progression holes you will likely be unable to do this without compromising the carb set up and an additional progression hole needs to be drilled.

[@steamwally]

Enjoyed that, thanks! The colour tune is a "fun" device and quite useful as you well showed. You will probably find it beneficial to tweak the mixture again after a spirited drive. The colourtune gets close, but nothing wrong with final tuning by feel, I often do that with ignition timing after the initial setting and a better result is often obtained. looking at the colour and condition of the spark plugs is the best indicator of what's going on and if any cylinder particularly has a problem. Out of interest, are you running the standard fuel pump? They are perfectly Ok. The only other suggestions I have are to check for air leaks, it looks kind of like a mixture imbalance between front and rear cylinder to me - my car was just the same before overhauling the SU's, one was too rich, one too lean. You could just pop the carb off and check that the throttle butterfly valves are properly fitted to the spindle and are both closing together. Also make sure there isn't a leak at the manifold gasket, that would do it. Have a good look at those spark plugs after a run, it will certainly help identify issues like that.

[@granblogismo]

Thanks for all the tips!! Will certainly have a look at some of those, getting to the point where a lot of stuff needs a bit of an overhaul but it’s tricky to know whether to try and get the MG tip-top or get progress on the Lotus!

[@timbutton4990]

You didn't mention balancing the chokes? I assume that each choke has it's own throttle butterfly? You really want to check the basic ignition timing & valve rocker clearances before looking at the carburation. To generalise a engine has to rich a mixture when it 'hunts' or surges at tickover which you touching the throttle. A lumpy tickerover means the mixture is too weak. I'm surprised if you don't have the invoices for the engine work? With the amount of money spent I would be surprised if a standard camshaft was still fitted?

[@granblogismo]

Yeah I was going to make a follow-up video about doing the chokes as I didn’t have an air flow meter when I made this, I do have one now. The chokes have their own butterfly but on the same spindle (not sure if that’s the right term) so not quite the same as twin SUs on how it’s adjusted, will look into it!

[@petercurtis1976]

Many thanks for this video. I have a 45DCOE fitted on my MGB by a previous owner. I’ve just finished a strip down and rebuild on the carb and have been scouring the interweb for a tuning tutorial. Perfect timing (not a pun)! I’ll have a look for a Gunson. Did I see that it’s size 14mm?

[@granblogismo]

Cool! Yep 14mm set is the one I bought 👍

[@timbosinius3653]

When I did a compete service on my 67 MGB GT yesterday I noticed that the sparks for Cyl 1 & 4 are quite black. Sparkplugs on Cyl 2 & 3 look quite good (light brown) and it idles fine. The same check with the Gunson that you did also looks good (blue). Do you have the same or is the color on all spark plugs the same? Not sure what I could do to change it.....

[@granblogismo]

Interesting!! Can’t remember what mine looked like the last time I changed them (back in April or May I think) but thought they were all quite similar. Did a quick google and seems that a few things can affect it, sounds like it’s not mixture as the 2&3 are fine but people say it could be valve clearances or weak spark so maybe HT lead or dizzy cap terminal for those cylinders aren’t in top condition or could even be oil but would think that would look wet rather than sooty? I’m no expert but I would start with any of the easy/cheaper stuff before getting too concerned, if it runs fine without smoke out the back then probably not anything major 🤷🏻‍♂️

[@voncoconut5293]

What about balancing the throttles? Getting the airflow equalised is an important part of the tuning.

[@granblogismo]

Indeed! Being a single carb (as opposed to twin SUs) I didn’t appreciate you can balance the chokes/barrels, there’s no separate throttle to adjust but apparently you can use the air bleed screw or something 🤷🏻‍♂️ got an airflow meter coming next week to check it 👍

[@petercurtis1976]

Hi Mark, do you have a fuel pressure regulator fitted to your BGT? Some people recommend them for use with Weber side draft carbs.

[@granblogismo]

Hi Peter, I don’t think I do but will look into that 👍👍 thanks!

[@stevo6900]

Still sounds rough mark are you running a different cam im running SUs on my 72 definitely idles better after a set up

[@granblogismo]

Yeah I’ve heard the Weber carbs are less smooth at idle anyway but the cam idea might have legs.... there was evidence of engine tweaks in the service history, lightened flywheel, different exhaust etc as well as club racing documents which might suggest stuff like that may have been done 🤷🏻‍♂️ certainly past MGBs I’ve had feel happy at 30mph in 4th gear but this one really isn’t, much happier in 3rd ie higher revs

[@stevo6900]

@@granblogismo that would explain it then my 72 is standard definitely pulls well low down in the revs yours does sound nice when you give it a boot though it's amazing the difference little things make swapped over the JR filters like KNs changed the driving experience I've yet to check if I need richer needle's weathers still wet need a good run

[@DavidScott-hi4fz]

@@granblogismo This is a great idea for a future video. I've been thinking about converting to a Weber45, be great to hear how it sounds going through the revs on the street. The big appeal of a weber is definitely the sound. Be great to hear yours on the run!

[@granblogismo]

Good idea! Need to get out in the ‘B again soon so may do this, thanks!