Dan, does it cough in both carbs? I know that you set idle mix etc with the
color
tune, but the only other thing I can think of is a gasket leak... and why only
at
certain times is not clear. If you are diagnosing a fuel problem it might be
worth your while to get or borrow a fuel pressure gauge and see what the pump is
actually putting out. If both the carbs are backfiring, then one might assume
that the problem is in fuel delivery, or an intake gasket leak that is being
caused or becomes extreme at higher than normal temps (maybe the header is
expanding that much more and pushing off the intake manifold... I'm guessing
here!). Have you tried the old "spray the carb cleaner around the gaskets and
see
what happens" trick? Got a lot of people rackin' there brains here!
Greg Burrows
Dan Neff wrote:
> datsunmike wrote:
> > The fuel pump has nothing to do with low float level unless you put in a
> > higher/lower pressure fuel pump.
>
> (I have a stock pump)
> Well, yeah. Assuming vaporlock could be A symptom of several possible
> causes of leaning out the engine, I was jumping from (eliminating)
> fuel pump problems, to possible (unrelated) float levels. Considering
> it runs great at all rpm's, and in cool weather (engine hot or cold),
> I find it hard to believe the floats are 'off', unless there's some
> minute adjustment to compensate for if/when the gas boils in the bowls.
> I don't think so, but I was wondering..
>
> > But I will tell you fuel level is extremely important for correct
> > running. Make sure your floats are good and set correctly. It would
> > change your mixture.
>
> I haven't heard/seen a way to adjust floats to perfection. Help?
> I've done the flip the lid over and measure float to lid when it hits
> the jet. Seems sloppy to me. Nissan manual talks about sticking some
> gauge thingy down the overflow hole to measure the depth of the fuel,
> but I don't see how that'll work without hitting the float!
> OTOH, we've demonstrated the mix is right (colortunes/exh gas
> analyzer), so perhaps the floats must be right?
>
> > How's your timing?
>
> Fine, contrary to any claims my wife makes.. :)
>
> I run it at 17 degs. It does ok at 15-16, altho it doesn't solve
> any problems (like vaporlocking), so I run it at 17 as it seems a
> little better at this altitude.
>
> dan.
>
> > ----- Original Message -----
> > From: "Dan Neff" <neffster189@adelphia.net>
> > To: "Roadster Listgroup" <datsun-roadsters@autox.team.net>
> > Sent: Tuesday, April 09, 2002 3:33 PM
> > Subject: Vaporlocking, part 2
> .
> .
> > > It's a beautiful 68 degree day out, so dropped the top and took the
> > > scenic route on my lunch break. Got back, left it idling (it's *thinking*
> > > about spluttering, but not there yet) and pulled the return hose at the
> > > firewall (pipe). Wow, NICE fuel flow! It took most of my thumb pressure to
> > > stopper it. Gas is cool too. Go figure!
> > > Well, next I'll check the return line from the fire wall to the tank,
> > > and make sure it's not plugged there.
> > >
> > > Wondering about the floats though. Could they be some minimal adjustment
> > > too low (ex: 1mm) - such that 90% of the time it's sufficient, but when
> > the
> > > gas starts to boil in the bowls, it leans out the carbs, even though the
> > > rest of the system (pump/lines/return) is flowing nice and cool?
>
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