Date:Apr. 09, 2023


Brief Description:Electric engine pre-heater build.

In the freezing temperatures early in the morning at the High Sierra Flyin Neil let me use his 1500 watt space heater hooked up to his generator to pre-heat N7ZK prior to departing the Deadcow Lake Bed.  Never having thought about pre-heating an engine the need immediately became apparent when the cold soaked engine sat in sub 30 degree weather overnight.  The Lycoming manual says 10 degrees is where preheating is required but they sell engines and don’t pay to maintain them.  If you ever wonder what the consistency of cold oil looks like just pour some 20W50 oil out of a quart bottle and see how thick it gets after leaving it in the freezer.  

Prior to departing for the “America is Square Tour” I decided to take an old space heater I had laying around and make a setup like Neil’s.  A quick stop at Home Depot and I had the necessary 6″ ductboard starting collar, 6″ to 4″ reducer, and 4″ x 8′ flexible aluminum dryer duct.  I was unable to source 6″ tube locally so I used 4″ with a reducer.  A little tin snip work to reduce the starting collar’s diameter so it would fit onto the fan’s face before a bit of aluminum tape to mate the two.  When Jim and I landed in Waterville, Maine and hooked the heater up to test the outlet we found the heater ran for a few minutes and failed.  Very disappointing!

When we got back to Orlando I went on Amazon and found a space heater that did not have a thermostat (it will continue to run regardless of temperature) and had a round face with a metal plate to mount the starting collar with rivets.  A few more minutes with the tin snips to further reduce the diameter of the starting collar and some LP4-4 rivets later and the pre-heater was completed.  I opted to scrap the 4″ tube and reducer and ordered some 6″ tube online.

Total cost $67.29 with a 4″ tube/reducer and $48.60 with a 6″ tube (no 6″ to 4″ reducer cost and cheaper hose).

Neil’s setup heating N7ZK at Dead Cow Lake Bed.

Original “surplus” space heater I assembled that failed before first use.

New $20  heater out of the box.

6″ ductboard starting collar sourced at Home Depot after using tin snips to modify end flange and collar ring.

End plate from heater ready to fit to starting collar.

Heater, 6″ductboard starting collar, 6″ to 4″ reducer.

Setup with 4″ flexible dryer tube.  For the final version I removed the reducer and went with a 6″ tube instead of the 4″ shown here.

China made heater specs.

Finished heater with 6″ tube.