I have the weber carb (DGAV) as well. My car backfired
right from the beginning (after I completed my initial
rebuild to get it running again)... The PO had blown
the engine.
Removing the air pump's drive belt eliminated the
backfire and added power just as you indicated. Here
in Florida, there are no emmission inspections so I've
just left it go. The car runs very well and the
exhaust is clean without the pump hooked up. I was
just thinking if there was something I could fix so I
could run the engine with the air pump-- why not hook
it back up?
I'm going to pop the hood and look for this "diverter
valve" tonight when I get home and see what I can find
out.
Regards,
--Rick
--- "R. A. Woodward" <conn@wctc.net> wrote:
>
> When I got my '80, the air pump hose was
> disconnected, and when I hooked
> it back up, I got the same backfire. It also has a
> Weber carb, and I was
> told at the time that the air pump was incompatible
> with a Weber. I was
> a bit concerned with the vacuum loss at the end of
> the exposed air pump
> hose, so instead of removing the pump, I removed the
> drive belt and
> reconnected the hose. The end result was a
> noticeable increase in power,
> especially on acceleration.
>
> As to the cat converter, I keep seeing the GO'Bs on
> HPTV replacing stock
> converters on various muscle cars with (street
> legal) "high performance"
> ones as part of an exhaust upgrade. Anyone know if
> similar converters
> are available for Spits?
>
> Rick Gregory wrote:
>
> > Atwell:
> >
> > My '77 has this exact same problem. It backfires
> while
> > idling down from high RPMs. I removed the air pump
> > belt to eliminate the back firing, but don't like
> the
> > idea of removing emission devices. Plus, my air
> pumps
> > works good I don't want it to freeze up.
> >
> > I thought maybe the check-valve on the tube behind
> the
> > air pump was shot.... allowing the back-fire.
> >
> > How could the catalytic converter be the cause of
> the
> > problem? Restricted flow?
> >
> > --Rick
> >
> > --- Atwell Haines <carbuff@nac.net> wrote:
> > >
> > > At 07:52 PM 6/13/99 -0400, Sam Gentry wrote:
> > > >We just got the 80 spit running and it works
> well
> > > EXCEPT: When we rev the
> > > >engine and let it coast down it backfires and
> gets
> > > very rich. Works great
> > > >if we eliminate the air pump. Any ideas? I
> would
> > > like to keep the
> > > >emission stock if possible.
> > >
> > > Sam,
> > >
> > > Chances are that your catalytic converter is
> shot.
> > > That's an expensive
> > > repair. :(
> > >
> > > I have left the air pump disconnected on mine
> > > because of that. Plus, my
> > > air pump is a bit noisy also. (Another expensive
> > > repair) It passed the NJ
> > > idle emissions test that way... :)
> > >
> > > Also, there is an off chance that your
> > > bypass/deceleration valve (front
> > > side of carb) has been blanked off.
> > >
> > > Atwell Haines
> > > '79 Spitfire
> > > Succasunna, NJ USA
> > > "If horrific means to make horrible, doesn't
> > > terrific mean to make
> > > terrible?"
> >
> >
> >
>
> --
> "History shows again and again, how nature points
> out the folly of man."
>
> -R. A. Woodward (conn@wctc.net)
>
>
>
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