Auxiliary thermostat........
 

BW,

If I were in your shoes, I would try to eliminate the auxiliary thermostat as a culprit to your overheating problem. It is either working or not but you don't know it!!!! Pull out the auxiliary thermostat and place it a water bath. And observe the opening temperature. Below is an illustration of four (4) thermostats (external) previous owners believed to be a good unit.
http://forums.pelicanparts.com/uploa...1379192681.jpg

You don't have to dismantle the auxiliary thermostat to do a test:
http://forums.pelicanparts.com/uploa...1379192858.jpg

Place the auxiliary thermostat/s in a water bath and heat it. You could actually watch the thermostat valve slide open or not during heating. A pen-light flashlight is very helpful in observing the movement of the thermostat (if it's good).
http://forums.pelicanparts.com/uploa...1379192952.jpg

The one on the left is fully closed (stuck), the middle is partially open, and on the right is a fully operational (good) unit. At water temperature of 187°F (+/-) the paraffin thermostat should start to open and fully open at 195°F. As you can see from the photo, some thermostat failed to open even at 195°F. Water boils at 212°F (atm).
http://forums.pelicanparts.com/uploa...1379192975.jpg

Tony

The OEM heater boxes were both connected but in installing the SSIs I just had the left side connected and the right side is connected in front but open at the back. There is no blowing into the engine compartment because there's nothing moving air in either direction on that side (as I understand it).
The external thermostat was replaced a year ago so I'm assuming its okay--there wasn't a change in temps from before the replacement.

You are guessing........
 

RW,

You are guessing and hoping for the best. The auxiliary thermostat may not be the culprit. But not until you eliminate it from the equation, it could be your problem. Who knows until it is tested and confirmed good. I have seen auxiliary thermostats stopped working all of a sudden!!! One day is was good and next it went bad. Just my two-cents.

Tony

I was able to drive my car quite a bit yesterday.

In the morning, about a 35min drive, mostly highway, was 50deg outside, car never got to 200.

Afternoon, ambient about 70, came up to exactly 9 o'clock which is 202 on my guage.

Night, was about 50 again, lower key ride, got to about 180 aside from about a 1mi blast to 125, and it rose to about 195.

NOTE: I have a heater delete plate (heat is deleted) on my shroud and have my heat exchangers taking in air (tubes still connected) at front but open to the air under the car at rear. (removed metal elbows and piping going into engine compartment, logically it doesnt seem like it would do anything) Before reading a prior post I never thought this could be adding to the cause...possibility?

My issue is I changed so many things on the car over the winter prior to this happening I can't simply undo/redo everything.

I wouldn't think un-connected heater boxes would lead to your overheating...

But I do have a suggestion, maybe your igniton wires are shorting and causing some mis-fires? I have seen this with too big of a spark gap also; the spark would rather go thru the wire than across a big gap. Did you put new plugs in during the clutch job, and maybe gap them larger than normal?

Chuck.H
'89 TurboLookTarga, 363k miles

Chuck,
My mechanic did install new plugs and wires. There doesn't seem to be evidence of misfires--the car runs really strong to redline--but he has the car now and I'll have him check. I'm having new brake calipers, pads and rear rotors from PMB installed ahead of a DE on Friday.