[DeTomaso] Bleeding the cooling system

MikeLDrew at aol.com MikeLDrew at aol.com
Thu Apr 4 20:15:03 EDT 2013


In a message dated 4/4/13 7 57 19, kirby.schrader at gmail.com writes:


> With this plate in the block, you can use any thermostat you want in
> place of the Cleveland type.
> 

>>>This used to be 'the thing to do', but it's not a popular modification 
anymore.   Among other things, it creates cavitation, as there is essentially 
no water movement in the cooling system until the thermostat opens, so the 
water pump just churns and churns away.   It also leads to hot spots inside 
the engine, as the coolant near the combustion process is heated up, but the 
coolant near the thermostat is still too cold to allow the thermostat to 
open.

JC Christian took me to school on all of this some time ago and I learned a 
lot from him.   Among other things, the 'hat' in the Cleveland thermostat 
doesn't completely block off the orifice in the block, by design.   A certain 
amount of flow through the engine (instead of through the radiator) is 
always desired.   If you look at the other Ford engine familes, i.e. Windsor, or 
FE, they have a bypass hose at the thermostat outlet that permanently 
routes a certain amount of coolant internally, bypassing the radiator, when the 
thermostat is fully open.   When the 351C thermostat is closed, there is a 
larger amount of water bypassed, and when it closes, it partially blocks the 
orifice, and the remaining area is about the same as the area of the bypass 
hoses on the other Ford engines.

Also, if you block the thermostat orifice, the block suffers from thermal 
shock when the thermostat finally opens.   It is incredibly hot in the hot 
spots, and then that hot fluid moves forward, and ice-cold fluid from the 
radiator takes its place.   WHAM!   That's really hard on the engine.   A 
functioning bypass means that the engine warms up uniformly and properly, and when 
the thermostat opens, the cold water coming from the radiator mixes with 
warm water circulating inside the engine to ease the temperature transitions 
until the system stabilizes at a set temperature.

The executive summary to me was:   Bypass good.   Blocked passage bad.

At least, that was my takeaway from the discussion.

Mike


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