The replacement carburetors have now had a check over by a man who knows about these things and he kindly soda blasted them inside and out to get rid of all the hardened gunk inside. All the components have been checked through and re-assembled so I am now confident that *this* time I have a way of squirting fuel into the inside of the engine rather than all over the outside.
The replacement carbs are from a later period than their predecessors but are still pre 1940 and fully acceptable. The only downside is they were designed to have an air filter on the front to keep out the dirt and grime, but my engine bay is narrower than it was originally and there is simply no room to fit an air filter. This leaves me with a very flat flange on the intake which is rubbish for air flow as it has to turn 90 degrees around the rim. A smoother intake is required and I could have machined the carburetor body to suit or I could modify a ‘velocity stack’ / ‘ram pipe’ from another application so that it does the same job. I chose the later solution and bought some cheap alloy ram pipes which simply bolt onto the front of the carburetor. They were designed to increase air flow within an air filter but they will meet my needs.
The best air flow for low revs would come from long pipes (100mm). Shorter ram pipes are better at high revs. No Ram pipes are not as good at any revs. The bulge in the bonnet allows me to have 25mm pipes with sufficient clearance to allow air to be sucked in. So whilst the short pipes are not really what i want – they are the only viable solution.
Below you can see one of the carburetors with no ram pipe which looks a bit….. agricultural and not what i want to see at all.
And here is one with the ram pipe bolted on
Although fully functional, it doesn’t look right or as good as it could. I think I need to replace those ugly bolts with a brass topped stud which will match in with all the other brass fittings. With that in mind, its over to the drawing board. Basically I need a top hat shaped head with a short stud partially threaded. Luckily I have a lathe which I seem to be using all the time now – who would have thought it was so useful. Below you can see the basic shape coming along
Which then gets a thread put onto the end, using a tool I adapted to fit into my lathe…
All that needs doing now is to cut the machined part from the length of bar and finish off the top. This uses a ‘parting off’ blade which you have to set absolutely square to the bar and slowly cut your way through to the middle. I have pretty much worked out how to do this now without getting stressed about destroying all my hard work. There is so much to learn but thats part of the fun for me.
And here you can see the finished part which has a slightly rounded edge purely for aesthetic reasons even though no-one will ever notice it.
After a trial fit to check it was the right size, I then proceed to make another 3 of these studs. In my usual fashion, I then aged them to look similar to the rest of the brass and this is the final effect which I think now makes the whole caboodle look rather sporty. I rather over polished the carburetor tops but they will soon dull down and the two aluminum cam covers will be similarly polished as so many people used to do in those days anyway.
Next I think I need to turn my attention to the fuel tank, fabricating protective mesh end panels, running in a fuel line to the engine etc…