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Re: [T3] Best dizzy for AT with carbs?


On 20 Mar 2003 at 22:45, Steven Ayres wrote:

> I didn't say it won't work well, I said it ought not to be his first
> choice. (Besides, he hasn't got an FI distributor.) Bob has a stock
> 1600 with stock carbs, so it makes sense that go with the stock
> distributor for carbs that he has in hand, certainly at least until he
> sorts out his problem. 

I don't think the carb dist he has is any better match than the FI dist he has.

I agree that if he is having problems it might be interesting if he could find 
exactly the right carb, although finding a 69 type 3 AT dist will be 
challenging, at the very best.  ;-)  

> I have a 1641 that's been extensively modified, therefore a different
> situation. I was commenting on the L distributor in a different
> context. 

I don't think that there is much difference in advance curve needs of different 
engines, but there are certainly lots of different ways to get there. I'm 
really concerned that you probably are running 40 deg of advance under some 
full load circumstances. I don't think that you realize this, and I suspect 
that you'd be concerned, too, if you did.  

I'd expect you to have trouble, for example, when you came to a big hill and 
shifted down to keep up your speed. Now you have high rpm (~30 deg mech adv) 
and WOT (~10 deg vac advance, but here I'm guessing that the carb you have 
gives enough vac under these circumstances to give you full vac advance.) Of 
course, if these carbs don't give enough vacuum to give much advance under 
these circumstances then it really doesn't really make much difference whether 
you connect that hose or not.

Or maybe your vac adv is not working for some reason, while Ben's is.... It's 
kinda hard to tell from way over here....

What you really want is ~30 deg adv going up that hill, but it would be nice to 
up that to ~40 once you're at the top and you can let off the throttle and let 
the engine relax again. This is what the later (vac/mech adv) dists do, and the 
later carbs that were made to work with them had their vacuum ports drilled 
differently so they would provide the right vacuum under the right conditions 
FOR THOSE DISTRIBUTORS.

OTOH, this aux vac advance was just a fuel economy add-on, which gives us a 
couple of extra highway mpg. Those engines will run just fine on just the mech 
adv.

-- 
Jim Adney
jadney@vwtype3.org
Madison, WI 53711-3054
USA

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