I was doing an oil change on my car (1985 z28 305 4bbl 5speed) and I noticed an orange rubber 3 prong plug. It was just hanging there. I found that plugs in below the rear spark plug on the drivers side above the oil filter, when I go to plug it back in it doesn’t want to go and won’t stay plugged in. I’ve cleaned it with electric part cleaner both on the make and female end. Car seems to run fine without it plugged in but I would like to know what it’s actually for as I JUST bought this car to learn 5speed on so I know next to nothing about it.

It’s a engine block heater.

It’s it something that’s okay to drive without? I tried plugging it in after cleaning it but it doesn’t seem to want to stay plugged in or plug all the way in for that matter

It’s aftermarket, yes it’s ok to drive without. It’s purpose is to warm up the engine on cold days without starting the car.

excellent man! Thank you. Now I just need to figure out why my speedo is reading high and the car is all set

You might want to start a new thread on that. I would maybe service the rear end and see what the gear ratio is. If it or the transmission was changed without the correct speedometer gear installed that would effect the speedometer. Unfortunately the gears are not available. Smaller tire size would make the speedometer faster.

yeah, stock transmission and rear end from factory but it is a 350 swap. It’s off by +5 under 50 and +10 over 50