Austin 850 performance conversion

[abri]

Time for a small update, it's been a while. 

The ram tubes have been completed and fitted to the car. I can't really say they've had a major effect on performance apart from moving the rev range where I experience the strongest pull slightly lower down. That's a good thing I guess. 

So, to take a step back, with my last update I mentioned that I'd be going with the short tubes because they'd need to fit in the air filter box. It just so happened that Vizard's tests showed that the short rounded tube is also one of the better ones for flow. 

I contacted a local engineer, took the air filter box as well as a spare throttle body to him for some measurements. We came up with the following drawings.



The the plan was to fit the ram tubes to the throttle bodies with bolts that don't come all the way through them. This was done in order to keep the surface of the mouth as smooth as possible. As you can also see, because of the shape of the filter box, the ram tubes could unfortunately not be made perfectly round. We needed to leave some space for the filter between the ram tube and the edge of filter box.

The end product looked like this



Here they are fitted to the carbs with the back plate of the filter box in place.




And finally, a shot down the throat of one of the carbs:
As you can see there is a bit of gasket sticking out and a small mismatch in the diameter. The final step before putting it on a dyno will be to clean this up with a dremel so that there is a seamless flow.


After this I have been trying different options to get the fueling and mixture correct. I've been struggling to be honest. I started out with some YY needles, recommended by someone who runs a similar setup in the UK. The car ran ok with these and accelerated fairly well at speed but was very sluggish off the line. I then tried some EB needles (a bit richer) which improved it a bit. My main issue is that if I adjust the mixture so that the sluggishness on pull away disappears, the mixture is way too rich at idle. Since I spend quite a bit of time in traffic, a mixture that's too rich at idle will quickly foul the plugs with soot. This has happened on two or three occasions, causing a misfire (not just with the EB needles). Lately I have settled on M needles (richer than EB). These needles are the exact same diameter at the section that's working at idle, so the idea was to adjust them so the mix is ok at idle but then to give it more fuel quicker to get off the line. With this I obviously assumed that it was it was a lean mix that was causing the sluggishness off the line. The sluggishness was even. It was not spluttering, so I think I was right with this assumption (and adjusting the mix richer reduced/removed the sluggishness).

Anyway, I also played around with different types of oil in the dashpots and found that heavier oil gave better results. So I'm currently running 20W50 engine oil. I did try the approved SU damper oil which appeared a bit thinner as well as an oil supplied by a local SU expert which was very thin. 

With the M needles the car runs very nicely at speed. The sluggishness off the line is not completely sorted out however, because I've had to lean the mixture out in order to be able to idle without fouling the plugs. At the moment it's still a bit rich at idle - so much so that I haven't been able to get a perfectly smooth idle. The tinkering continues...That's what you get for not keeping original parts on the car

The final setup looks like this with a choke cable recently hooked up as well.



And on the inside it looks virtually identical to the original



I have to say that it runs very well and would easily run to max on the speedometer assuming the little 850 won't go bang. I need to fit a rev counter as well