[6pack] carb problems

[Greg Tatarian]

Hello,
This is a long-running debate, and I'd like to add my 2 cents.

Having rebuilt about 7 pairs of ZS carbs for Triumphs and Lotuses, and 
having in the past worked on a number of SU carbs for my cars and for 
other people, I'd say each has their own strengths and weaknesses, and 
that the problems with ZS carbs are usually related to lack of 
maintenance, which sometimes results in wear that can't easily be 
compensated for.

Specifically, the air valve assembly and the body of the carb are 
matched during manufacture, but a bad diaphram, bad air cleaners, high 
mileage, or lack of maintenance can cause the tolerances to increase to 
where the performance suffers. A common problem is when an owner or 
mechanic rebuilds the carbs but swaps the air valves between the bodies. 
The bypass and temperature compensating valves are really common problem 
components when they go out of adjustment or the gaskets or diaphrams 
fail, but when properly maintained and adjusted, both perform their 
duties well. Many problems with performance and driveability with TRs 
are related to worn linkages, or other smog equipment still left in 
place (e.g. coolant temperature vacuum sender in radiator hose. A pretty 
good range of needles is available, but not as many as SU. The ZS are 
shorter, so can fit tight spaces better than most SUs.

I run ZS carbs on my Elan and my TR6, have rebuilt them (and spare 
sets), and maintain them, and performance is great. Having said that, I 
haven't tested any motors on a dyno to compare properly tuned SUs vs. ZSs.

Cheers,
Greg Tatarian
1971 Lotus Elan S4
1974 Triumph TR6
1974 Alfa Romeo GTV (on Webers)




On 6/1/2010 2:38 PM, Bob wrote:
> All,
>
> Is it me or are these ZS carbs a real PITA?
>
> I made a decision very early in the restoration of my 72 6 to convert to HS6
> carbs.
>
> The reason at the time was I understand SUs with a 3 and a 4 in the garage so
> why bother trying to figure out something new?
>
> So ever since I joined this list and the 6pack forum, it seems all I see is
> problems related to ZS carbs and the emission stuff.
>
> I am starting to think my decision to use SU HS6 carbs was a good move.
>
> Bob
> _______________________________________________