lean engine

[thomas g. warner]

When you are talking about the possibility of screwing up your engine with a
to lean mixture, spend a couple of dollars and have your repair shop put
their gas analyzer in the exhaust and check the mixture. Why be penny wise
and pound foolish? Engines are expensive.

>Chuck,
>
> While the old carburetor gives better gas mileage, are you sure it is rich
>enough to avoid engine damage? You don't want to burn any valves from
>running too lean just to pick up some MPG. It may be fine, but you should
>keep an eye on it. I would check the plugs after a trip to see what they
>look like. Fairly clean to a brownish color is good. Black/Sooty is too
>rich. Totally clean, white deposits, or a slightly burned electrode could
>all indicate a lean mixture. The plugs should be checked after a normal
>run. Shut it off as soon as you stop instead of letting it idle,
>otherwise, you will be reading the idle mixture instead of the normal
>running mixture. This is not the most accurate method of gauging your fuel
>mixture, but it should give a reasonable gauge.
>
> Another, even less accurate gauge would be to see how red the exhaust
>manifolds get when pulling an incline. This method would entail driving
>with the engine cover off, so BE CAREFUL if you try this method. They will
>probably get red even with the correct mixture, but if they are really
>glowing cherry red, then it is probably too lean. OTOH if they don't get
>red at all (very unlikely), then it may be too rich.
>
> Zak
>
>

>>oil flow and wonderful oil pressure (not a false one either) I changed to
>>the old carb today and we went 250 round trip up the coast and back. 1/4
>>tank of gas. Much better than a tank up and a tank back like last week
>
>
>
Tom & Marg Warner
Vernon Center NY
1976 palmbeach

 

[zachary zehnacker]

Tom,

We use a DFI fuel injection unit on our GMC, so our oxygen sensor gives us
a pretty good idea if we are too rich or too lean. Most repair shops will
find something wrong if you want them to, and Chuck would probably end up
getting the carb rebuilt again if he took it to get analyzed. While the
exhaust gas analyser is an accurate way to check, it also can't tell you
the mixture under heavy load conditions (pulling a hill) unless you put the
engine on a dyno or rig up some way to drive around with the analyzer
attached. We have used the spark plug method for many years on our race
cars and have had good success. The exhaust manifolds are also a good
indicator if something is significantly off in the mixture. These methods
should get the mixture close enough (or at least on the rich/safe side) to
ensure that engine damage will not occur. They may not result in the
maximum power or efficiency, but they are a good check to make sure you are
a little safe/rich.

Zak

>When you are talking about the possibility of screwing up your engine with a
>to lean mixture, spend a couple of dollars and have your repair shop put
>their gas analyzer in the exhaust and check the mixture. Why be penny wise
>and pound foolish? Engines are expensive.

 

[philip l. stewart]

We use a DFI fuel injection unit on our GMC, so our oxygen sensor
gives us
> a pretty good idea if we are too rich or too lean. .... While the
> exhaust gas analyser is an accurate way to check, it also can't tell you
> the mixture under heavy load conditions (pulling a hill) unless you put the
> engine on a dyno or rig up some way to drive around with the analyzer
> attached.

Cinnabar Engineering in Sandusky, MI, has just such a rig, i.e, one that
is portable and analizes the exhaust while the vehicle is under whatever
load conditions you drive it at. If they are close to you, its a system
worth checking into.

Phil Stewart
'67 Transmode