On winter warmups.

I’ve been having a dog of a time getting a smooth idle when it’s cold out. Anything under, say, 50 degrees, and it’s a bear. Plenty of power when running, but when returning to idle, it tends to dip down, then recover. Sometimes it pulses.

I know the carburetor has issues, and I’ve got a solution for that hopefully coming in tomorrow. Still, though, I need to fix the root problem, and that’s the lack of intake preheat.

Every single website that sells carburetors and intake kits recommends that you don’t do a single center progressive on the Type 4, because there are no exhaust setups stock that offer intake preheat tubes. Some people who do center carbs try to fix this by welding their own intake exhaust preheat tubes up, or add “thermal reflectors” (aluminum sheets) over the intake pipes, so block heat is trapped. Others make pipes that go from a shroud around an exhaust header, and run it to a cardboard box built around the air cleaner, and I myself may do something like that. However, the vast majority of people simply live with it, or don’t drive in the winter.

I’m going to trial something different. I don’t know how long it’ll survive, or if it’ll even work, but for $40 it’s worth a shot.

First thing, I stripped out the old heater booster fan wires and relay. The way it worked is a switch on the front heater lever grounded pin 86 on a relay, which was powered from the alternator voltage regulator output, to prevent you from draining the battery without the engine running. This relay switched a big honkin’ fused lead straight from the battery, to the heater fan. However, being 44 years old and in an engine compartment led to these failing often.






Superior German Engineering :godwinning:

I cut the heater fan wiring loom back until I was past the crispy bits, and wired that into a stock 5-pin automotive relay. Bad pic, ignore the kapton tape (taped up a test light)



I’ve wired this down to a set of four, 10x200mm, “7.5W” 12V heaters. Currently they only have a small bead of arctic silver [knockoff] compound in a strip on the bottom, and I’ve kapton-taped them to the intake runners.



So, with the engine running, I can pull the once-unused (used to open the flaps to the exhaust heater boxes) heater lever all the way down, and it clicks over the relay, which turns on the silicone heating strips. Before buttoning everything up, I got the engine running, and tested it. They warmed up right quick, to the point they were nearly too hot to touch. This is hopefully going to be much better than having icy-cold runners. I’ve honestly seen condensation on them after a freeway run to work. I also smeared a thin coating of copper RTV on top and in the sides of the silicone strips, to give them a little more sticktivity for the next week or so of testing. If everything works out, I’m going to wrap some insulating fiberglass/silicone tape over them, and call it good.

I’m aware the best place to put them would be on the bottom of the runners, as that is where gasoline vapor is probably condensing and running down to, but that’s a right pain in the dick with everything installed. Plus, as-is, if one burns out, I can rip it up without disassembling anything. I have no idea what kind of lifespan these little (I’m assuming) nichrome-mica heaters have.


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