Exhaust port color update (what is that noise?)update, Light gray vs black Options

[cwpeden]

Just chasing a noise on my 2.0 that sounded like an exhaust leak but doesn't look like one once the exchanger is off the head.

However I notice that the #3 port and pipes are light gray instead of black.

I tightened the exhaust before taking it off with no change and it doesn't look like it was leaking there. Could leak between the head and cylinder cause it to be lean? and also go away once its warmed up? Or is this generally a problem that is cause by intake leaks?

[r_towle]

#3 is typically the hottest cylinder, that is why the CHT sensor is mounted on that part of the engine.
Being the hottest, it will be the lean one.
The whole system is designed based upon that head temp.

If you are running djet, I can't recall what you are running, you can add a resistor inline on the CHT to add resistance which will richen up the mixture of the whole engine, across the whole range of rpms.

The best way to do that is to put an accurate temp gauge on that head, and even better on the exhaust port to measure the temp.
Then (what I do) is install a variable POT inline with the CHT, and turn it up until you get th temp Down to what you need.
Then use an ohm meter to measure across the POT to see what the resistance is, and go buy that resistor....

This was a standard item on certain 1973 models....
I have done this twice, it works well enough.


It could also be a vacuum leak on that cylinder.
Rich