I’m afraid that my vacuum advance pipe had seen better days so I decided to replace it (it was split mad thus not creating a vacuum!) however, when going to take it off the end by the carb/manifold, the small tube it slots into came with it Is there anything I can do about sorting this? Unfortunately, it is completely flush so I cannot fit anything on, even the tiniest bit
Do you have the metal vacuum pipe with a screw at the dizzy end or a plastic push fit at both ends - won't make any difference to the fitting at the carb end, but could be useful background. Also, which model carb do you have (if you don;t know, then what year is the car?
From what you say, it is the metal pipe that sticks out of the carb body that has broken off? I've never seen that before, but can understand why it poses a problem.
The SU reference catalogue shows a diagram of the carb body but does not list any separate fitting to connect the vacuum pipe. I suggest that you remove the carb and drill a small hole into which you can insert a small piece of copper tube (around 1.5mm ID). Make sure that it is an interference fit in the carb and will fit securely inside the connector rube for the vacuum pipe. If you have access to model makers tools then you could tap the body and cut a matching thread on the tube. In either case use a heat resistant adhesive to ensure that the pipe is airtight and cannot come loose.
Alternatively, you should be able to pick up a complete carb at a scrapyard or autojumble; or via club spares.
Phil,
Very interesting indeed! and well to be believed. It tallies with my own experiments.
When I converted my MG TD XPAG engine to a PCV closed circuit breather system to try and reduce the oil leaks, the first ting I did was to tap both sides of the manifold as the TD has a balance orifice in the centre of the inlet manifold. I connected up a temporary vacuum gauge to measure the actual pressure. I started the engine and thought that the gauge needle gauge was going to go into orbit! Obviously due to the pulsations mentioned in that article- although the XPAG has a standard cam which is not highly profiled. This was solved by inserting a restrictor ( a cigarette butt filter ) in the line to the gauge. I was able to get a constant reading of-700mbar at idle. When the PCV valve was installed and without any restrictor I couldn't get the car to idle properly and the vacuum pressure in the crankcase was -120mbar. All sources of infiltration air with the exception of the rear crankshaft scroll were block off. So no proper idle but the oil leak had stopped! Where air is drawn in,- oil cannot flow out!
I began making brass restrictors for each side of the manifold going down in size until I could get a decent idle. I stopped when I had a 1.7mm restrictor each side of the manifold which gave a good idle so obviously was just enough to damp out the pulsations. The improvement on the oil leak was great success and it has been that way for a couple of years.
I used to have an eggcup full after each run and now I only have to drain my drip tray once a season.
From a torrent to a trickle!
Regards
Declan
Is there anything I can do about sorting this? Unfortunately, it is completely flush so I cannot fit anything on, even the tiniest bit