Distributor Vacuum advance

[garyf]

I have recently been reading an old technical article from theTSSC Courier magazine about Performance and economy improvements by blanking off the vacuum advance pipe to the Distributor.

Has anyone tried this on there Triumph 4 or 6 cylinder engine fitted with a Lucas Distriibutor?

I have got the standard engine in my Vitesse Mk2 and was going to give it a try and see if I could notice a difference, is this modification likely to cause any damage to the engine?

Regards

Gary

[mark spit]

Yes, it's a 'performance' mod.  You disconnect it then set the max advance at the appropriate rpm, say 3 or 3.5k rpm.

However the vac advance is primarily to give more advance at part throttle settings when the mixture gets leaner so you get a more efficient burn of the fuel.

My fast road engine was set up this way by the builder.  However I have since changed to megajolt which does take into account engine vacuum.  Much more fuel efficient since.

If your car runs fine with the vac advance connected, probably best to leave it.

You won't damage it as the maximum advance you'll get with it disconnected would be less than before so highly unlikey you'll get any pinking (pre ignition) which can cause damage.

Yours
Mark

[Nick Jones]

Can't see how this can be possibly regarded as a performance mod on a road car when it will actually decrease part throttle power and increase fuel consumption.  It's there for a reason.

If you have part throttle pinking issues then this could help, but should really be addressed properly by fitting a vacuum capsule with less aggressive charcteristics (Mk 2 Vit has quite alot of vac advance).

Nick

[piman]

Hello Gary,

that is not a sensible suggestion. If you want performance, put your foot down, the the vacuum advance does nothing because there is not sufficient vacuum to activate it, so, in effect it is as though it is disconnected.

Certain engines do not have a vacuum advance, like my P.I. as there is very little vacuum anyway, Aston's did not bother with the DB5, as I presume they felt their customers wanted performance rather than economy, so the engines were set up without it.

Alec

[garyf]

Ok Guys, thanks for the feedback.

I will leave the vacuum advance pipe fitted, the Engine is set up at the factory figure of 10 Degree's BTDC and it runs well with no pinking or running on when using the Shell V-power fuel.

However if I use standard fuel it runs on and I can notice a definite loss of smooth running.

I tried the Aldon Octane booster when I first put the Car on the road but didn't notice any difference?

I will stick with the Shell V-Power petrol.

Regards

Gary

[Pete Lewis]

the vac unit is purley a ecconomy device and designed to give around 3/4 mpg cruising throttle
the vacuum is made as air flows  over a small hole near the throttle plate creates a vortex any more than 1/4 throttle and vacuum is next to nothing.
reduce as Nick says the max vac advance would be best option the numbers on the lucas can give its vac start point eg( 4 ins Hg) the max vac (eg 11)and the max degrees  eg(7)
if you ran you car inth 1960/70 on 95 it was considered mower fuel so dont expect much, they were designed to run on 100 ron fuels  tesco pumps show there's as 99  get as high as you can optimax shows as 97ron    its down to preference but for 95 you have to retard the settings in the book and pretend youre  in outer mongolia with less performance and very hot running exhaust gases  peter
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