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spark plugs & thermostat


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I am rebuildung a 4.2V8 at the moment for my RRC.

1) I´ve read that it makes sense to keep the alu engine block at a low temperature - to limit problems that are caused by different expansion of steel and aluminium in the crankshaft and cylinder-liner area.

The original 3.9 that powered my RRC should have a 88deg. thermostat. There are also a 82deg and a 74deg available. I will use Megasquirt so there will be no coldstart-enrichment worries with a different coolant temp. Given the above argument it seems logical to use the 74deg thermostat.

Will there be any negative effects ??? In which vehicle was that 74deg thermostat used ? I do not use the engine and car to race (the recommendation was from the DesHammill-book which deals about race prep of the RoverV8)

Should the 82deg. be the best "allround performer"? I think it was used in the V8 Defender.

2) The standard spark plug for the 4.2 V8 is the RN11YC. This is a Resistor-type, 14mm-thread,car-engine,standard nose, copper core - plug. The "11" reads for a fairly high combustion temperature in the cylinders OR is it the other way round ???.

If I used another thermostat, like going from 88deg to 82deg or even 74degrees, would I have to take another spark plug ? Like: the engine block stays cooler then - so I have to use a spark plug which retains more heat or the like?



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