bubbles

 The Fiat twin cam cooling system evolved over the years from a thermostat in the head to a three-way setup external to the engine. I don't know the engineering behind it, but when I put the 1972 engine in this 1978 Spider, I decided to convert it over to the external setup since it was then the same as all the other cars, which is useful at times. Once set up correctly, these cars have excellent cooling capabilities - I've never had any issues with it in the summer heat, not even when racing. 

One oddity is that I am not sure where the radiator in this car was originally from because it doesn't actually fit in this car. It's about an inch too narrow.  Someone had (very kindly) given it to me and I had already recored it before realizing with a good deal of aggravation that it seemed to be from a different car. Since the only real problem was that it didn't quite reach the mounting bolt on the passenger side, I just made a spacer for it to bolt it on. I also converted over to a larger (and lighter) fan than the original Fiat metal-framed stocky yellow 4-bladed unit.  I don't like how those aftermarket fans just ziptie to the radiator so I used some more flat stock to make mounts for it. The mounts are ugly, but they work. I might pretty them up at some point, but I doubt it. 

One of the things to be aware of with Spiders is that the radiator is lower than the engine, which leads to problems if you haven't fully bled all the air out of the system. My simple solution is to have a flushing tee in the top heater hose that is the uppermost point of the cooling system. I fill, burp all the hoses, and then top off through the flushing tee, and that does it. 

 The first problem with this new overheating issue was that I, like a big dummy, had installed the thermostat the wrong way round, and it was not in fact stuck closed. There's an arrow pointing at the nominal outlet tee on this thermostat, but turns out that's not actually how it goes. That was easily fixed, but I still had a problem with overheating, and it did not appear the thermostat was opening to allow coolant flow from the lower radiator hose back into the pump.  After a few rounds of careful bleeding, the problem persisted. I theorized that new thermostats (with which I have little familiarity) perhaps seal far too tightly, causing an air bubble in the lower hose that prevented coolant contact with the thermostat, which in turn does not open as it should. 

There's a trick for this, drilling a tiny hole in the thermostat plate to allow air to escape (some other engines have this by design, some even with tiny little float valves to allow air but prevent liquid).  I commenced to drilling, and on the next round everything worked just fine.  

I also fixed the thermoswitch wiring to the fan that was falling off, tidied away the wiring harness, flushed the whole thing and refilled with the green stuff and distilled water, and that little problem appears to have been solved. 

The car has not repeated the ignition malarkey, but I moved the new ignition relay over behind a brace further away from the exhaust, in case heat was causing it to seize up or something. It is more likely that there is some stray voltage through the pink wire, or the ignition switch is not disconnecting cleanly. The power usage of the relay is so much lower than that of the coil, it might be causing some latent electrical shorting issues to be more apparent.