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Distributor vacuum advance goes no-where?
damajin - 29/4/09 at 11:36 AM

started looking over the engine last night in preparation for giving it a tune up (I bought the car second hand) and noticed that the vacuum hose from the distributor has been cut to about 3in long and just goes to atmosphere.

Is this right?
Will this give me power / performance / running issues?

Cheers
D

blakep82 - 29/4/09 at 11:38 AM

it will affect the advance curve... its supposed to go to the intake manifold i think (been a good few years since i saw a vacuum advance dizzy)

omega0684 - 29/4/09 at 11:40 AM

blake is correct, the vac adv pipe from the dizzy should be connected to the Inlet manifold vac pipes

Mr Whippy - 29/4/09 at 11:41 AM

the dizzy will only be advancing the ignition using the centrifugal advance then and not the load sensing effect of the vacuum

Basically you’re loosing power. Is this engine multi carbed?

flak monkey - 29/4/09 at 11:49 AM

Incorrect, the vacuum can be left disconnected on the dizzy, and is recommended if you are using twin carbs or throttle bodies as the pulses from the manifold cause timing fluctuatuations. The proper thing to do here it to buy a vacuumless dizzy, but leaving a std one disconnected is fine.

Essentially the vacuum advance brings in much more advance when the engine is cruising where you can run higher advances due to the leaner mixture meaning you get better fuel consumption.

All that disconnecting the vacuum will do is increase fuel consumption. But this is more beneficial than erratic timing if you are running on DCOEs etc.

If you are using the standard single carb though, keep it connected.

[Edited on 29/4/09 by flak monkey]

Mr Whippy - 29/4/09 at 12:07 PM

you can actually buy dizzys specifically for no vacuum advance like the 009 ones fitted to the bug engines

damajin - 29/4/09 at 12:37 PM

quote:
Originally posted by Mr Whippy
the dizzy will only be advancing the ignition using the centrifugal advance then and not the load sensing effect of the vacuum

Basically you’re loosing power. Is this engine multi carbed?


Thanks to all for the advice. Engine is a 1600 x-flow with a single Webber DCOE 40.

From the sounds of it, it won't be too desperate in the immediate future to have it hooked up, but if I have trouble with emissions etc it may be something to look at. Out of interest, how to the dizzies that are designed to work without this differ, if anyone knows?

Cheers
D

flak monkey - 29/4/09 at 01:06 PM

Dizzy without vacuum advance has a solid top plate inside rather than one which is in 2 pieces.

David

britishtrident - 29/4/09 at 01:12 PM

Vac adadvance is essentially an economy device to allow weaker mixtures at light throttle opennings --- vac advance is practically zero at full throttle.

You can convert a lucas vac adavance distributer to non vac advadnce by fitting a one piece bas plate or by lockking the two parts of the base plate together with a screw or pop rivet.

Davey D - 29/4/09 at 02:28 PM

my old fiat uno 1.0 IE had vacuum advance on the dizzy. didnt seem to make much/any difference if it was connected or not

02GF74 - 30/4/09 at 07:23 AM

what emission are you worried about? pretty sure SVA test is visual only