I’m currently waiting for Australia Post again, this time to deliver some glass tubing to replace the broken drippers on the Bebe so in the mean time I am having another crack at the Bug’s low speed chug. In the tradition of fixing one thing and breaking another, this has only been evident since the new diff was installed as I’m now cruising at lower revs.
Up until now I had mistakenly believed the following from the publication “Grand Prix Technicalities” put out by the Bugatti Owners Club UK:
That does seem logical until you think about the alternative firing order of 1,3,4,2, so if Carb A was connected to cylinders 1 & 2 and Carb B was connected to cylinders 3 & 4
| Cyl | 1 | 3 | 4 | 2 | 1 | 3 | 4 | 2 | |
| Carb | A | B | B | A | A | B | B | A |
You get “two successive sucks followed by an interval” (or a Swedish pop band) as stated in 4.17. So it’s bollocks, strangely Ettore went to some trouble fitting two inlet valves a cylinder then siamesed them, making it just about impossible to predict the outcome. They just run better with one carburettor, so I have ordered a new manifold for hopefully the right reason..
Colin Chapman had the answer for siamesed ports on the Austin 7 engine see here for the story.
I must have far too much time on my hands, I have included a few pics from this week of the Bebe, note the echos of Bugatti in the tappet cover and the unbent banana tappets. Also checked the valve timing which was spot on and read this great article on Model T valve timing which makes a lot of sense in slow revving low compression engines. Lastly people talk about ABS, ESC and even ESP making their car safe, the Bebe on the other hand has automatic ignition cutout if the oil drippers are turned off, now that’s a safety feature.
Cheers
Mark
Here is a thermal image of the radiator after idling for a bit, I should have put something behind the radiator as you can see the heat from the exhaust. But you can see the heat going from the top and down the LHS of the picture then cooling as it goes toward the right.
