Running on the lean side can be good for top end power, but it makes the
engine run hotter. And it also can cause throttle hesitation and surging
at constant RPM operation. Ideally you want it lean enough for strong
top end, then richen it as needed to get smooth throttle response.
But I've never used exhaust temperatures to adjusted carb mixture. The
carbs I've worked on had an "idle drop" procedure to set the idle
mixture. You close the screw all the way, then open it a specified # of
turns (usually 2-3 turns). Then start the engine and let it warm up
completely. Attach a HIGHLY accurate tach to the engine. Then slowly
open (richen) the screw and you'll see the RPM climbing. Continue
opening the screw until the RPM reaches its max value. Then close the
screw until the RPM drops about 50 RPM from its peak value. Then, from
that setting, open the screw a specified # of turns, usuall 1/2 to 1
turn.
After you adjust the mixture like this for each carb, you then attach
vacuum gauges to the intake and synchronize the carb throttle plate
positions so the vacuum in each is the same.
The basic procedure is the same for most carbs, but the details (# of
turns) varies from carb to carb and engine to engine.
Good luck,
> -----Original Message-----
> From: owner-ba-autox@autox.team.net
> [mailto:owner-ba-autox@autox.team.net] On Behalf Of Scot Zediker
> Sent: Monday, May 06, 2002 11:38
> To: james creasy; ba-autox@autox.team.net
> Subject: Re: exhaust temp gauges, where to find info to use?
>
>
> IIRC, the higher the exhaust temp, the leaner your fuel
> mixture. I'm not absolutely sure, but your 1400 deg. temps
> are probably okay. You can enrich the mixture if the temps
> are worrying you, but of course you will use more fuel.
>
> If you run any endurance races, running richer might actually
> be a good idea. It'll help to reduce stress on your engine
> by keeping temps lower, and you'll shoot flames out the
> tailpipe on overrun ;)
>
> Scot
>
> ----- Original Message -----
> From: "james creasy" <Black94PGT@pacbell.net>
> To: <ba-autox@autox.team.net>
> Sent: Monday, May 06, 2002 11:22 AM
> Subject: exhaust temp gauges, where to find info to use?
>
>
> > ive got two exhaust temp gauges on my 2.4 liter I6 with
> dual SU carbs.
> they
> > appear to be on the front and rear cylinder header tubes.
> >
> > how do i use these, or where can i get info to learn about
> this? with
> > the unshaved needle floats, they ran about 1400 degrees at 4K RPM.
> >
> > im new to carbs.
> >
> > thanks!
> >
> > -james "EFI" creasy
> > thevenom.net
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