[DeTomaso] Thermostat and restrictor

[MikeLDrew at aol.com]

In a message dated 1/30/10 9 54 5, wdemelo at cogeco.ca writes:


> How does the restrictor plate under the stat housing work? On my orig 
> motor I can see it has a quarter size opening. On my friends Cat, it is sealed 
> completely.
> What is it's purpose.
> 

Your friend had his opening sealed off, which prevents the engine from 
warming up normally.

The 351C thermostat has a 'hat' on it.   When the thermostat is closed, 
water is allowed to flow around the bottom of the thermostat and through that 
opening in the block, letting the water circulate throughout the engine.   As 
the thermostat heats up and opens, the hat sinks down and eventually blocks 
off that opening; the water is then prevented from circulating in the block 
and instead goes forward to the radiator.

People get in trouble by installing a standard 351W thermostat instead of 
the 351C unit.   They appear identical except for the hat.   If you do that, 
nothing ever blocks off that opening, and something like 25% of the water 
flow (a guess) just keeps going around and around in the engine, never going 
forward to the radiator, which leads to overheating.

If course, if you block off the opening entirely as your friend has done, 
that lets you run a normal thermostat.   But it prevents proper warmup and 
may make bleeding the cooling system more difficult too.

Mike