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On 26 Apr 2004 at 19:12, Mark Seaton wrote:
> I'm still getting worse than expected MPG despite new pistons cylinders and
> valves, and I think its due to my ignition timing. The car has been running
> ok but I checked the timing again anyway. I've heard Jim say that the vac
> advance shouldn't come into effect when the car is stationary- only when
> cruising at partial throttle. Well mine definately does come into play as
> soon as I rev the engine and it shoots up. If I keep revving, the advance
> goes up to 40+ deg! (I put a paint mark on at about 35) With the hose
> disconnected it maxes out at my mark.
I'd say that your idle advance setting is too far advanced. You should set the
timing such that you can get about 30 deg of advance max out of the mechanical
advance ALONE. Adding in the vacuum advance can bring this up to 40, but I
don't care for the fact that you can get this while standing still. I wonder if
you've got the wrong carbs (with the wrong vacuum pickoff port) for your
distributor.
> So I really don't understand whats wrong. The carbs are now the original
> ones and have been re-built, but the same has happened with 2 other pairs of
> carbs. If the balance were slightly out, could that cause a too strong vac
> signal? (I checked the balance and on my synchro-tester it seems very good).
> I checked and the arm on the vac can has number 507 stamped on it- does
> anyone know if this is the right can for a late ('73) european spec dual
> carb engine? If its not, does anyone have one?
I don't have specs on Euro engines, so I don't know if that's the right can or
not. It's not used on any US type 3s. I think you're set too far advanced and
that will get you running hot and reduce the gas mileage, I assume, as it's
past the optimum.
> I disconnected the vac and ran the car on a longish run this weekend and it
> ran better than before. Timing is stock 7.5 deg adv at idle and otherwise
> the dizzy is in very good health. Any ideas?
Is this the stock dist? The carbs and dist have to be matched. If they're not,
then differences in the vacuum advances can get you in trouble. I have the
impression that you were actually the one who figured a lot of this out for us.
--
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Jim Adney, jadney@vwtype3.org
Madison, Wisconsin, USA
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