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Block Heaters

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twas_brillig

Jedi Knight
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Our BJ7 has an immersion type block heater in it, from the original owner; our Bugeye came with one of the ones that replaces a headbolt. I doubt if anyone drives vehicles like this in the winter anymore (back in the day, our BE was our sole vehicle for one winter), but I also thought that there might be some folks interested in a paper I ran across recently, written in 1972 at the University of Saskatchewan https://library.csbe-scgab.ca/docs/journal/14/14_1_15_ocr.pdf And this is the only automotive type site I sign on to.
Briefly: the authors instrumented up a straight six and a V8. Two hours gives you most of the heating effect; five hours pretty much gets you to the maximum temperature. And the combustion chambers got to the highest temperatures. And the oil in the sump didn't much warm up at all.
It was brass monkey weather here last week (-37C/-35F one morning) and our 2009 BMW X3 didn't want to crank (no block heater) but fired immediately.
I'm assuming that the important aspect of a block heater back in the days of carbs would have been that warm cylinder head, helping the fuel droplets to atomize/vapourise/ignite. But if the water jacket is warming and the oil in the sump is still cold, why does the engine crank better with a block heater? The cylinder walls/piston rings will be warmish; the crank & bearings will be colder than heck; the valve train will be warmish, etc. etc.
Knowledge would be appreciated. Doug
 
Depending on the design of the heater ... I'd think an engine would start more easily in winter if the oil in the cylinders were warmer (less friction) than still cold. Cranking would have less resistance if the oil along the piston sides were warmed.

(Despite living in Wisconsin for over ten years ... I have no knowledge of how my block heater actually did its job - just logic.)
 
For an Ohio winter or two, I added a "block heater" to the sump of my '99 M Rdstr. Cold (stiff) oil was deemed the culprit of its centrifugal supercharger failing, according to Vortech, its manufacturer, and there were times when it was relegated to being parked outside overnight.

I bought a commercially available magnetic block heater, but BMW engines have aluminum sumps, so I found some thermally conductive epoxy and used that to bond a small (postcard sized) piece of steel to the front of the pan. My only objective WAS to preheat the oil, as I otherwise had no issues with cold-weather startup, warmup or setting off driving, I just needed to appease the supercharger!
 
You can get a block heater that inserts in the dipstick tube:


Kat's Crankcase Dipstick Heater 23" 90 Watt​


Being resistive-type heat they are power-hungry.
 
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