View single post by Esprit2
 Posted: 08-17-2017 08:08 pm
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Joined: 05-01-2005
Location: Minneapolis, Minnesota USA
Posts: 337
The engine needs to come up to normal operating temperture to run right, and to prevent moisture condensation build-up inside the engine. There is such thing as too cool.

The thermostat's rated temperature is the point at which it starts to open, and the engine will normally run a little hotter than that.

85C (185F) is low-normal, IMHO. 90C (194F) is pretty normal. 105C (221F) isn't going to do any short term damage, but if your engine makes a habit of running that hot, you should find out why and address the cause before it becomes a problem.

The JH 907's water pump has a pretty pathetic little impeller that's prone to cavitation. The later Lotus 907 impeller is an improvement, but still underwhelming. Installing a 910 Turbo water pump's impeller is the best hop-up you can give your otherwise stock pump. The 910 impeller is taller, and won't fit in the JH housing. Just have a machine shop shorten it's nose to the same overall length as the JH impeller, and the rest of the rebuild procedure goes as before.

The 910 pump, and the Federal Esprit's 907 pump use a smaller 4.5" diameter pulley (verses 5.25") to spin the pump faster and increase circulation. But the two pulleys have different bolt patterns, and therefore require different hubs on the pump. Changing pulley sizes is a decision to make when the pump is apart for a rebuild.

I strongly recommend the 910 impeller and 4.5" pulley for all 9XX engines operating in hot climates.

The majority of my 907 overheating issues have been gauge related, including the sender and voltage stabilizer... mostly the stabilizer. When it fails, or it's ground connection corrodes/ loses continuity, then the voltage goes high and all the gauges it feeds read high. The temp gauge for sure.

Tim Engel