Early Chim 4.0HC thermostat

[captaintact]

My Chim 4.0HC runs at a steady 70deg on the motorway and the fan comes in and maintains at 90deg in traffic. There appears to be two main thermostats for this car. 74deg and 82deg. Presumably i have the 74deg one? Should i replace with the 82deg one? (Most modern cars seem to run at around a steady 80deg on a motorway journey? Page 110 of "the bible" suggests using 82deg version for more efficient running.

Does this have anything to do with whether it is a Serp or pre-sep engine? How can i tell? Mine does NOT have an expansion tank for the radiator. Is that the difference?

[Ribol]

A serp engine has a single "ribbed" belt, the earlier engine uses "v" belts.

[captaintact]

Cheers so mine is a Serp engine. Should i have an 82deg thermostat?

[spend]

I'd always stick a 74C stat in TBH, but ISTR RT advising me they should be in the hotter pre-serp engines many moons ago.

[Ribol]

captaintact said:

Cheers so mine is a Serp engine. Should i have an 82deg thermostat?

I have had both, the lower one is the better option IMO.

[captaintact]

Cheers. Is the ECU mapping more efficient for running at 70 or 80 deg i wonder? And indeed, is it a different map for the HC model since it's bound to have different characteristics?

[Ribol]

captaintact said:

Cheers. Is the ECU mapping more efficient for running at 70 or 80 deg i wonder? And indeed, is it a different map for the HC model since it's bound to have different characteristics?

These cars warm up so fast and run so hot that in practice it makes little difference, hence there is no downside to having the lower one.