can't for a minute see how this sorted the issue,if the air supply to the HE's wasn't capped of I would say lack of cooling air to cylinders and oil cooler but they were capped !!!.
I run headers with block off covers on both sides of my engine runs great oil temps,this is known to provide better cooling besides.
Have worked with aircooled engines for 30 odd years this one has got me stumped

Tub, the heat exchangers on the stock headers effectively double wall the headers preventing cooling air from carrying heat away from the header and tubes. Then the exterior of the heat exchangers is also heated


I can see where this is a much bigger heated mass and a much bigger heat radiator than just the air flow cooled header tubes. The result would be more heat transferred into the heads

Would like to see an analysis by my thermo dynamics prof but That's my theory

To take gereed75's theory a step further, if the heat exchangers can't allow the hot air to escape it's going to back up the positive air flow. As long as the hot air can get out, either to the cabin or out the vent in the flapper box, there's positive air flow and it won't be a problem.

The reason this isn't a problem in a car with headers is because there's no restriction of the cooling air flow.

Years ago I rigged an electric fan in the spare wheel well to blow heat through my 68 Bus heat exchangers in an effort to keep from blowing engine fumes into the cabin. I ended up having to run the fan all of the time because the exchangers would get hotter and overheat the flex hoses I was using and cause a burning smell. I can see how this could cause additional heat in your situation.

That would be the esteemed Grady Clay of Denver Colorado.
Proud to say I met him long ago.
He left this world in 2014
RIP

Wow, what a difference. Nice find! Thanks for sharing.

So they basically cease being a heatexchanger without the flow from the fanshroud,the heat builds up but has no where to go right ?? so it transfers back into the engine, hot heads = hot oil =high temp right ?.
Thanks for helping my clear this up Perry and gereed75,good I have that in my thick head know .

When I pointed my IR thermometer at the backside of the oil cooler near the bottom I got readings near 300 degrees (after driving it) before I put the ducts to the heat exchangers on the car. After I installed the ducts (and driving again) that same area of the oil cooler read 235 degrees!!!!!!! The oil cooler is only a few inches above the exchanger. Imagine how much heat must have been radiating upwards onto the bottom of the cylinders..:-0

That says a lot

Glad you got that worked out. I believe that that is Puffs old car I had faith that it was solid (looks right too!!)

It is Puffs old car. He was kind enough to pass along the needed ducts!

I can't wait to put this theory to test in mine. It will have to wait a while for weather to improve in my area. I hope it works as I have battled higher temps in my 2.7 than I would like to see.

Don't know who puff is lol ,what ever way real nice car ,go out and enjoy