At what displacement are external coolers needed?, Building an alternative engine for my six Options

[Speedo]

I have read that the general consensus is above 180 hp an external cooler is needed.
I am at a crossroads with the 2.2 T I am building. I have 2.2 S pistons and cylinders and and cams. If I stroke it I get a higher cr 2.4 S. If I don't stroke it I get a decent 2.2 S which would still be a nice choice. I have everything I need for the 2.2, but if I stroke it I will need to source a 70.4 crank. Curious what the board thinks about the "red line in the sand" for needing cooling. It goes without saying that I am not interested in cutting on the six for a cooler up front.
Having said that...I spoke with a friend over the weekend with a 76 911 with a 3.2 transplant that doesn't run a cooler. He says his temps never go over 210...which I question as I have a stock 74 2.7 with a modified pulley setup that runs 200 but will show 230 when pushed. I think I need to measure his temps with a pyrometer to double check his temp gauge. (IMG:style_emoticons/default/bs.gif)
Tell me what you guys think! (IMG:style_emoticons/default/idea.gif)

[gereed75]

I do not dispute any personal experiences or recommendations on this subject and they seem to be all over the map. I can only relay my personal experience

I run a 2.4 with 9.5 CE pistons ( actually measured static), ported T heads, mod Solex cams, single plug, 40 Weber’s and I also run conservative ignition advance 26-28 BTDC.

Nothing but stock cooler, temps never above 210. I do not normally do a lot of extended highway cruising which seems to be the worst condition for cooling. Stock four cylinder side shift trans.

I did run an under trunk floor cooler for awhile. My thread is on here somewhere. It effectively dropped temps about 15 -20 degrees and I ran 20 minute track sessions with it no problem.

My opinnion based on this experience and a lot of experience running aircooled flat four Lycoming in aircraft applications - every engine is different, mixture, compression and ignition timing have a huge influence.

Bottom line - I think you can run a 2.4 S without extra cooling if everything else is good. By the way, this is a great street motor, good clean torque and VERY entertaining from 4500 - 7000 rpm!