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?

#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

Thanks Rich, how are you feeling?

Its a 73 2.0 with all original FI and resistor.

So it seems what I think is a leak is temperature dependant(goes away when engine is warmed up).
It sounds like an air leak like a whistle or squeak most noticed when engine is under load and not fully warmed up.
Could this be a leak developing at the cylinder head?

Just grasping at straws hoping to pull the right one before I have to pull the engine.

Could just be a leak in the muffler to head seal.

I always start with new copper gaskets.
Anneal them.
Hang HE loosely front and rear, then,doing all four together, I tighten the HE to the head.
Then, after that is done, I hand the muffler and get that fitted and tightened

Then I go back and,tighten up the HE again.

Thanks for asking, feel like I had a HA.

Done
Done
Done
Done

no change

What does a leaking head gasket sound like? Or at least the beginning of one?

PS: 9 months tomorrow....

Update:

So after checking the head studs and finding one that was a little loose I thought I had the problem found.

Nope.

Turns out one of the exhaust nuts was not even touching the HE flange. It was torqued to spec, just a blemish on the stud was preventing it from going all the way down. I just happened to notice it as I was moving the light from under the car while getting the engine ready to pull.

Hope this helps someone else in their quest...

So, pull the heat exchanger from that side and take a good look at that exhaust port and copper gasket, if it has been loose all this time it blew out the gasket and may have blown out a groove in the head also.....thus a loud leak.

Yup, replaced stud and gaskets.
Its odd how a small exhaust leak can sound like so many other things.