And also how DOES one spell vaccum ?
Anyhow I had a mechanic tune the side draught 40s today (did a great job). Anyhow he mentioned that he didn't like the whole vaccum advance set up. The manifold is bored on the tube close to the fire wall (as one would expect). This sends a pulse to the diaphram on the dizzy. The problem is of course that the pulse is only sent when the number one cylinder is taking a breath and not when numbers 2,3 &4 are doing their thing.
Soooooo........
All datto owners of much great experience and fountain of all knowledge....okay I'm pushing it a bit.
What do you suggest.
Cheers

Quote:
V A C U U M [VAC- yoU- UM]

If you are using vacuum for the distributor, then it needs to be 'ported' vacuum from the carb, not from the manifold. Your mechanic should really know this already. If you are using Webers/ Solex's/ DeLorto's, then forget it, you won't have enough vacuum to suck fizzy drink up a straw anyway & none of these carbs came with ported vacuum fittings.

If you are using an IR [individual runner] manifold, then any vacuum signal, such as for brakes, should come from ALL the runners

Yeah thanks, Its a twinweber set up. So should I just take the hose off and bung the hole on the distributor and the manifold. It sounds like the hose isn't doing anything at the moment anyway.

Bye the way I'm looking for a new dash. Can you remember who makes them, some guy in Ipswich.

You dont really need vac advance on a worked engine, its just kind of a economy thing (so ive been told). Or if you are going to run it the port should be as close to the butterfly/s as possible.

If I remember rightly, it's 120Fly who makes them. From all indications, he does a good job of it too.

At light throttle settings, & at cruise speeds, the engine can take advantage of more advance, so the high manifold vacuum is used to 'suck in' some more advance & the end result is improved economy.

If you check, you will find that the legendary triple Weber Valiant R/T models did not use boosted brakes. This was done simply because with the Webers, there was NO vacuum to speak of to power the vacuum brake booster. I'm tipping that your engine will be much the same, so plug the hole in the manifold & run without the vacuum advance feature.

If you can afford it, get the engine dyno'd & have the distributor re-graphed to best suit your engine with mechanical advance only.