I have some questions and actually have some info to share with the list.
First the question. I have two problems which may be related. The mileage
I get is consistently 17 mpg and it sounds like this is much lower than
other Spits. Also, during the first five or ten minutes of running the car
I get backfires when I take my foot off the accelerator to shift gears.
It's not loud "banging" backfires, but more of a "slap-slap" sound as the
engine decelerates (someone on the list once used the term "wet farts" which
probably also describes the noise I am hearing). I have a '79 Spitfire with
a stock ZS carb with a water choke. I recently did a carb rebuild and had
an LBC mechanic tune and adjust the carb afterwards (I had this same problem
before the rebuild). I have checked the performance of the
deceleration/bypass valve according the directions in the Haynes manual and
it seems to be performing as designed and doesn't need adjusting. I also
recently had the car smogged and it was way below the permissible limits on
CO and hydrocarbons so I assume the mixture is set pretty good. Any
thoughts?
And now something helpful to share with the list. Awhile back someone had
mentioned the benefits of changing out old spark plug cables. I got a new
set and compared the resistance of the old ones to the new ones using an ohm
meter. I can't remember the exact numbers, but I seem to remember the old
ones being at least three times higher than the new ones if not more. Since
putting the new cables on the car seems to start easier and I think it runs
just a tad smoother (not included the first 10 minutes of run time described
above). It was well worth the $16.
Bob Bollinger
79 Spitfire
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