Vac advance blocked off. No tube fitted?????

[Prince Brainier of Meccano]

New toy( Vitesse Mk2 1998) (1969 really) has the vac advance stub at the carb blanked off and the tube completely missing.  Gave the vac advance unit a playful suck  and it moves and holds, so no leaky diaphragm.  Is this normal to allow it to run on modern lead free lower octane fuel or just a thing not noticed by the previous owner?  Has a sensor type point replacement but no programming module.  simply a points wear remover.

Edited September 23, 2020 by Prince Brainier of Meccano
date wrong

[Pete Lewis]

the vac unit gains around 4 mpg  in old money  has no effect on performance just advances up in a cruise throttle drive to gain some economy 

if the dizzy is working roughly to its designed curve and you set the timming to its optimum for the fuel octane you use there is no worldyly reason to abort the contaption

if you  do get pinking with the timing set correctly and you use 97+ ron fuel  then the vac unit might require less light throttle advance than that of 50 years ago but most dont have any problems most would just retard a degree or two to take the edge off any pinking  

the dizzy vacuum is produced by the throttle plate position over two small orrifice in the throat and nothing to do with manifold vacuum.

Pete

[Iain T]

I would refit the vac tube, it's  designed to be there for good reason. Does one of your carbs have the brass tube where the vac tube fits? 

Iain 

Oops just seen your post says it's blanked off and missing! I don't know I'd Burlen sells the tube if not buy some brass tubing and make your own. 

[Nick Jones]

It's probably been removed to cut down the pinking.  The Mk2 vacuum capsule has a fairly aggressive advance curve and pinking can be a problem with modern fuel (not so much if you use the good stuff).  I would reconnect it and see what happens.  If it pinks horribly on light throttle then try knocking back the base timing anything up to 4º from the book figure.  Beyond that you might want to check the overall condition of the distributor (frequently weary), revert to disconnected or swap in a the capsule from a later 2000 which has a less aggressive profile.  Personally I'd take the necessary steps to get the vacuum advance working properly as it helps part throttle torque, throttle response and fuel economy.

Nick

[Pete Lewis]

if its a delco dizzy you can reduce the max by cut a fibre washer and clip it over the exterior vac capsule operating piston   maybe only the early versions 

D202 etc 

Pete

[NonMember]

4 minutes ago, Pete Lewis said:

if its a delco dizzy

Should be Lucas on a 2L Vitesse, Delco on a GT6

[Prince Brainier of Meccano]

On 21/09/2020 at 15:24, Iain T said:

I would refit the vac tube, it's  designed to be there for good reason. Does one of your carbs have the brass tube where the vac tube fits? 

Iain 

Oops just seen your post says it's blanked off and missing! I don't know I'd Burlen sells the tube if not buy some brass tubing and make your own. 

Its only the plastic tube that's missing not the brass stub.  That just had a cap over it.

[Prince Brainier of Meccano]

Thanks for all the advice and help.  It is a Lucas dizzy.  Not driven it since I reconnected the pipe as time didn't permit.  Started OK and now back under cover.  Fixed a fuel leak at the same time in the front carb so that will need resetting.