Tu3S Vacuum Advance

[fourbanger 2]

My vacuum advance pipe dropped off the carb and the car now has much more top end and half the fuel economy, leading me to think that it wasn't working correctly to start with and the previous owner might have played with the timing to compensate.

I've tried sucking on the pipe and it makes no difference so I'm pretty sure at least the diaphragm is gone, if not the whole mechanism.

Anyone know where I can get a replacement?

And does it make much performance difference to run full advance and block off the carb?

[And 15 1 Cars]

It only works on over run and idle to retard the timing for fuel economy if say using twin carbs you would remove it any way it won't harm any thing but I would check the timing settings are correct as you may have to much advance if it was set up with it connected and working, I think it was meant to have the timming set with vacum off but not 100% on that as I never had mine connected and is pined inside my dizzy,

[tdr_1976 41 1 Cars]

Funnily enough, I have literally just had the timing light on my TU3S to check the timing. The book says 8 degree advance with the vacuum advance disconnected.

Edited February 25, 2016 by tdr_1976

[Tom Fenton 1,542]

Vac advance works at light throttle eg cruise. As soon as you floor it, the vacuum is gone and you are back to base timing. It helps economy a lot on cruise so it's worth getting it working really.

[Mid-life 205 0 1 Cars]

Sounds familiar. I just bought a Rallye with a mild cam and Webber. In diagnosing a flat spot I found the Vac was shot. To stop it sucking air and messing with the idle mix the previous owner had plugged the vac pipe and re-fitted it. :-) nice.

 

I took the distributor to these guys

http://www.ignitioncarparts.co.uk/

 

Who repaired the Vac and spotted a broken bob weight spring at the same time.

 

Not big money and at least you know you still have the right distributor.

BTW I measured 11 degrees at idle when warm.