</font><font color="blue" class="small">( The in-line heater will work just as well)</font>
Just curious Junkman, have you read anything to support this or have you ever used both an inline and a block heater on the same engine to compare them? I'm not trying to be difficult; I haven't done either myself. I just wonder what you're basing this statement on. Though I teach other things now, I do hold a certificate to teach Physics. It seems very counterintuitive that an inline coolant heater could be as effective as a block heater. The thermal flow from an inline heater would be limited to the transfer through the coolant in the hose up and into the block. The majority of the heat would radiate off into space from the hose. A heater in the block would have a much smaller amount of the heat radiate off into space. As the heat leaves a block heater it has only a very short distance to flow before entering the block itself. The iron from which the block is constructed has a much higher thermal conductivity than the coolant itself, therefore the heat should be quickly transferred throughout the entire engine.
You made the comment that once the fluid is flowing that the heat from an inline heater should be quickly transferred into the block. The thing is, the fluid is not going to flow until the starter turns the crankshaft. Once combustion begins, the buildup of heat is self-sustaining and an external supplemental heat source is no longer needed. The only way an inline heater could get the majority of its heat into the block is if the water pump could be activated independently from all the rest of the engine for 10-15 min. prior to cranking.
The block heater provides the heat where it is needed, inside the block itself. The compression of air by the piston during the compression stroke concentrates whatever calories of heat that already exist into a smaller space, thus raising the temperature. Much of that heat instantly flows into the cylinder walls. If the cylinder walls are too cold, the temperature increase from the compression still does not raise the temperature to the combustion point of the number 2 fuel oil. Having the temperature of the cylinder walls elevated by use of the block heater means that fewer therms of energy flow into the cylinder walls during the compression stroke, leaving the compressed air hot enough to ignite the #2 fuel when it is injected into the compacted and pressurized cavity between the head and piston.
This is my theory, but it is an educated theory. Anyone who has evidence to the contrary, whether through measured tests or anecdotal experience, I would very much like to hear it.
