What are the specs for the coolant drain plugs on either side of our small blocks? These are the ones with the allen head and are only about a 1/4 inch long.

I'm missing one and need to know what I can replace it with until I can find it.

Thanks,
GC

 

One (driver's side) has a plug. The other (passenger side) has the knock sensor.

 

They're 1/4" NPT. I like to put a petcock in instead of a plug though, makes it a lot easier to drain the block.

 

Knock Sensor!!!!! Ah-hah. I didn't think there were two plugs when I stripped it down. I just have to find the knock sensor now. At least that will be easier to search for at the parts store if I come up snake-eyes.

Lesson learned. Label parts better!!!

 

Doesn't the knock sensor screw into the head?

 

No, into the drain hole in the block. The temperature gauge sender screws in the the LH head, the fan switch screws into the RH head. The threads on the knock sensor are much too small for the coolant ports on the heads.