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Re: [T3] Carb Conversion?


On 23 Feb 2001, at 14:09, Douglas_Brashear@amsinc.com wrote:

> I have a '73 Fastback (manual transmission) that wasn't running so
> well, and I just spent like $300 at a local shop to have them tune it
> up, trouble shoot a bunch of things, and get it running.  It is a
> totally stock engine aside from a header exhaust.  Now it runs about
> at about 80%, I'd say...the engine only has 42K miles on it (car sat a
> while before I bought it), has great compression (130 PSI in all
> cylinders even when cold), and sits inside a car that should last many
> more years.

Sounds like you got a good one.

I wish I were closer to you. Working together we probably could 
have gotten you to a better state for less money. The biggest 
problem with the FI is just finding someone who understands it and 
is honestly interested in helping you. It sounds like you have a 
great car, so I hope you stick with this effort for awhile.

I think I have one list member coming here from NYC sometime 
early this summer. Want to make it a caravan?

> Basically, if I could get the FI running 100% then I'd stick with it. 
> Since the remaining problems involve some surging at idle, and slight
> surging/lack of power at speed, I'm thinking I may have a leaky
> injector.  I may consider new injectors in the future to see if that
> helps.

It is probably not an injector problem, but until I hear more I'm not 
sure what to suggest. Have you measured the charging system 
regulating voltage?

> Anyway, back to the question...I've seen Weber Type III carb kits
> available, but have no idea what's involved in converting the engine
> to carbs.
> 
> - Can you fit a mechanical pump to the stock case?  Or do you have to
> go with a Facet electric fuel pumps? - Are there any wires already in
> the rear harness that must be connected to the carbs?  Probably not if
> they don't have electric chokes... - How difficult is the tuning
> procedure? Are there any special tools than can help? - Do you need a
> special throttle cable (perhaps longer than the stock one)? - What do
> you do with all the breather hoses that lead into the stock air filter
> (from the heads, from the case, etc.)? - What source of carbs/parts do
> people recommend?

I have heard of cases that wouldn't take a mech pump, but I've 
never seen one. You can run any wires you need from the coil. 
Tuning is a significant learning curve and you can't count on the 
carbs being jetted correctly for your car as they come out of the 
box. Parts are available, but probably only by mail order. They are 
also getting harder to find every year. Special tools: Uni-Syn carb 
syncronizer. Most people just ignore the hoses that are left over. 
Not a particularly responsible idea since these are emissions 
related, but there is not much else you can do. You'll probably 
need a different cable, or perhaps the kit will come with an 
extender. Carb linkages are a big deal and I hear that the quality 
can vary a lot.

> One con I've heard of:
> 
> - The carbs have no choke, so starting the engine in cold conditions
> (i.e. 0 degrees F) can be a pain. - what else?

I don't think the Weber carbs have any vacuum or choke provisions.

> The pros are obvious:
> 
> - Somewhat easier to maintain than FI, and easier to troubleshoot -
> Parts readily available - Less to go wrong - Probably better mileage
> than I'm getting right now (about 22 MPG) - Increased power - what
> else?

I don't think they're any easier to maintain, but there are a lot of 
people out there who at least think they understand carbs better 
and can troubleshoot them more easily. Both systems have 
significant learning curves. Increased mileage is likely, but at the 
cost of increased emissions. Increased power is very probable.

There are clearly people on this list who have had both positive and 
negative experiences with both systems.

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

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