Most cars have some form of a bypass. The older American t-stat had a
hole of about 1/8" in the butterfly valve so that hot water could pass
over the bi-metalic "pellet" that actually opened the butterfly. This
was to prevent overheating as a consequence of the time constant
differences between that of the pellet and the rate of heating of the
Triumph (and Volvo) used the larger bypass to do two things:
1. insure the simultaneous, even heating of the head and block
2. speed up the heating of the engine.
In this plan, the shroude style cuts the flow through the bypass and
diverts it to the radiator as needed. It in fact more dynamicly and
efficiently balances the temperature in the engine. Essentially, a very
good engine design. The only problem was the use of the bellows styple,
vs. a simple bi-metallic pellet to provide the method of opening.
As an aside, a cracked head in a TR is a great rarity, unless it was run
>In a message dated 1/11/2007 7:14:18 AM Pacific Standard Time,
>It's a fact that thermal stress can cause cast iron to crack. It's a fact
>lack of coolant circulation leads to excessive thermal stress (aka hot spot
>It's a fact that the bypass allows coolant to circulate when the thermostat
>closed. What more do you want ?
>Its a fact that the correct tstat for a TR3 was shrouded.
>Its a fact that the shrouded tstat has been hard to get for years
>Its a fact that a lot of TR3 have blocked bypasses to help them run cooler.
>Its a fact that there are a number of TR3s with cracked heads.
>Best Regards, Mike Moore
>ps-My Jaguar XK engines use the same setup, only scaled up.
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