Carbtune use

[William2]

I tried my recently purchased Morgan Carbtune out today having first warmed the engine up. I found it easy to use and a great piece of kit. I adjusted the mixture screws and idle balance screw as instructed and managed to balance cylinders 2, 3 and 4 to almost exactly the same levels on the gauges and as high as possible. However, no. 1 cylinder appeared to be about 2cms Hg higher on the scale. Might this be due to the servo/headlight vacuum takeoff from the inlet manifold? Would it be better to temporarily remove these and blank off the two tubes so they do not interfere with the vacuum of the manifold? Maybe a 2cms difference is acceptable and has anyone else using a Carbtune had a similar issue with no. 1 cylinder?

[john.p.clegg]

William
My carbtune in use..

carbtune.jpg (78.08 KiB) Viewed 1397 times

ended up a lot better than the photo after " setting" the butterfly shafts.

John

[1963Turnerjohn]

Where are you taking the vacuum feed from - the inlet manifold runners?

[john.p.clegg]

If that question is directed at me...Yes ( dellortos with no "tapping" )

John

[William2]

In my case I am connecting the carbtune directly to the carbs, My main question was is it better to remove the servo/headlight manifold hoses and plug them so that you can get an accurate reading on no. 1 cylinder?

[john.p.clegg]

Willaim
Yes,just in case there's a leak.

John

[alan.barker]

William,
seems like a good idea. Then when you reconnect if the reading changes you know you have a problem with the non return valve on Servo or Headlamps
Alan

[William2]

Just to follow up on this thread that I started, it made no difference to the manometer readings when I disconnected the servo/headlamp vacuum feeds. Still got a higher reading on no.1 cylinder compared to others no matter how much I adjusted the idle mixture screw. However, when I revved the engine slightly above idle, all manometer levels were equal so I think I will leave as is. I did go back to testing no.1 at idle with my Colour Tune and adjusted the mixture to give the correct colour. Overall the engine pulls very well and idles smoothly. The only noticeable thing when driving is a very slight hesitation off idle but barely noticeable.

[mbell]

J Still got a higher reading on no.1 cylinder compared to others no matter how much I adjusted the idle mixture screw.

Do you really mean the idle mixture screw? I'd be adjusting the air bypass screw (on 40DCOE151) to balance the different cylinders not the idle mixture screw. On older carbs you'd need to drill holes in the throttle plate to balance them between the different barrels.

Will be doing this job on my car soon as I can get a few minute to do it.

[William2]

My DHLA 40 carbs don't have idle bypass screws. I have decided not to mess around drilling holes in throttle plates because the engine is running very smoothly so I will leave everything as is.

[William2]

My DHLA 40 carbs don't have idle bypass screws. I have decided not to mess around drilling holes in throttle plates because the engine is running very smoothly so I will leave everything as is.