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Re: [T3] Carbs vs FI


Your going to dual carbs on a dual port ?
Your engine will probably have a higer rpm
speed. Probably more power. This is due to the freer
breathing intakes that just suck air directly.
optimum for this setup is cool air from the outside
and the old type oil sump air filter. 
Usually most setups are like this big carbs, tiney paper
air cleaners and hot intake of air.

The larger than modest carbs give you good top end
and sometimes poor low end due to low vacume.
This setup is better for stick shift because you can rev it for take
offs but in automatics it can bogg you down. 
The small paper filter is a barrier for good bunch of air
and this air is prewarmed by the engine compartment and
can cause knocking if the carbs are leaned a little. 
The vacume is not steady since it is directly above the 
small runner, this can cause an uneven idle, sounds
like a hot cam. There are usually flat spots in the RPM
range aggrivated by the wrong add on distributor and 
race cam. Some peoples "hot" setup almost make the car undrivable
and if you are not properly versed in tuning them , hard starting
and low power when cold engine will happen.
In addition to all of this, your gas mileage will go down since
you must run richer and have to overcome the flat spots with 
more gas pedal. 

The stock dual carb works fine because they are small, get cool air
from outside,  have a low restriction aircleaner, smaller throats for
more vacume and better fuel control but less upperend power.

The EFI has no flat spots and makes the cars drivability very
very pleasant . The stock system is not a rocket but performance 
is all around outstanding and it is easily modified by "frankenstiening"
parts and odd tweeking, for much more speed . Drawback is that it
seems more complicated than carbs by design : wires , 3 sensors,
brain, two switches and injectors. This is actually quiet easy to understand
by reading about , looking at schematics from the bently manual,
and taking every component apart for understanding function and 
inpecting for condition. Once you recondition a system, it will
give you decades of dependible operation.

The aftermarket carb setup , to be fully satisfied, you must either be
"doctor carburator" or "Vw carburator god" or "know one of these"
For the common mechanic most aftermarket setups are always in the process 
of tunning and never arrive to the desired perfection.
Some people I have heard are really good at jetting , tunning , selecting
and modifing to the point that they have awesome all around performance and
good gas mileage. 

It depends on skill of the carb dude  to be satisfied with the carb setup.
Call a carb dude specifically on this list so you can have the other side of
the 
story I am VW efi dude but a Detroit monster carb dude.

I have heard alot of complaints about changing from EFI to carbs by
people that felt they lost some pleasant drivabilty. The change was
done because no one or they were NOT able to fix a problem or continual
failures
associated with wiring or components on their system. Lack of experties 
and knowledge is the cause of EFI replacement.

If you are really going to go for the change , talk to a real good carb guy
that can help you with info on his near perfect setup and will not 
say later "I don't know" or " it should have not been doing that".
Good luck for the search of more zooom! Or just modify the 
EFI for more zooom!
 

LEON MARTINEZ

1969 SQUAREBACK EFI/AUTO
SAN DIEGO AND TIJUANA

 

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