What voltage goes to the intake nanifold heater?

Never thought of 555 timer. I used to use them all the time for my flashing model marker lights and strobes. But i've moved on to pograming arduinos for that now. But that would do even better. I can add an ambient air temperature sensor and have it kuck on only if the temp is below X.

Sorry for bumping this thread, but I wanted to let anyone who may be reading this thread for research know. After I swapped on my 2100, I was having this same problem this winter, and I suspect what was happening was that the intake manifold was too cold, until the coolant passage warmed it up, and the fuel in the air charge was condensing on the walls and floor of the manifold. I learned that my intake heater wasnt working, and I was going to run a toggle switch to the relay for it (square relay next to the battery on my 83 eagle), but after diving into it a little, I discovered that the relay had just been smashed, probably during the engine swap. I cleaned up the plug and slapped a new universal type relay on it, and it worked perfectly. Its still a little doggy coming off idle when its cold, but not bad enough to kill it anymore, and really what can you expect from a 35 year old carburated car? Anyways long story short, the intake heater helps A LOT in cold weather, so if your car is taking forever to warm up, make sure its working.

Yeah, can't leave it on for long! After the coolant temp comes up it needs to be turned off. A temp switch should be in the circuit to cut power once temp is up. That will solve the problem of burning it up! A 165 degree switch would be nice. Just wire into the power side of the relay. Most of those switches are NO and close when temp hits the threshold, so might take another relay, but easy enough. 

oil pressure switch has three terminals. One is for the light - when there's no pressure it grounds and the light comes on. The other two are a NO SPST switch. That means normally open single pole/single throw.
There's power to one of those other two terminals. In many Eagles, etc. the other goes to electric choke. This ensures the choke doesn't heat unless the engine is running.