What do you consider the optimal operating temp (coolant temp - measured right after exiting the head) for an Alum headed twink? What is a perfectly safe range? And what temp thermostat do you usually run? (DocE - feel free to chime in anytime :-)

That Vegantune is certainly NOT "average", Allen!

185~195*F would be a nice "range", methinks. Temp at outlet will (usually) be around 195*F+ I'd expect. I normally go for a low temp t-stat... 180*: Florida in July is decidedly not where these things were designed to operate. Your climate is about the same. But there are more than a few factors determining temp's... don't wanna get me started on ethanol, etc.

Alloy heads are kinda sensitive to the higher temps (+200*) so I err on the side of caution. Combustion efficiency is likely suffering a bit, but I don't have any desire to warp "unobtanim" here. With all that monitoring rig ya got, you should be able to tweak the mix to keep it from goin' so lean as to get ugly, yet not so fat as to bog 'n load up. Webers are part voodoo so I tend to jet 'em a bit fatter just on G.P.

I've had very few temp issues with my own cars, cooling system flushes annually and always a coolant mix. If we got an overheating car in the shop, the usual problem (other than a t-stat malfunction) would be a radiator goober'd up from lack of maintenance.

Thanks doc. That's pretty much what I was thinking, but I searched the net a bit and couldn't find anything to verify. I'm sitting idling a lot as I'm starting to tune now and I get really nervous when the temp gets up around 200. I'm comfortable with 195, 200 I get worried, and when I see its crept up to 203 when I've looked away for a bit it scares the crap outta me! (the head, cam carriers, etc are definitely "unobtainium" - though I have seen two complete engines for sale on the other side of the pond in the past couple of years.) I wasn't sure if I was over reacting or being justifiably prudent. I guess I'll try a system flush this weekend and see if that will bring it down a little.

Prior to this conversion, I had to mix aviation fuel to keep it from detonating under high load/high RPM. I'm running it on 93 pump gas now - hoping I can tune it so I don't have to visit the local airport every few weeks. (one of the reasons I did the conversion) I'm thinking the lower octane fuel may be causing it to run a little hotter than what I'm used to?