305 Block Drains

**pajeff02** · 08-22-2010, 04:58 PM

I am flushing the coolant on the Monte Carlo and I have a block drain about mid-engine on the driver side, just above the oil pan rail. On the passenger side, I cannot locate a block drain -- however, there is a "knock sensor" that sets almost across from the driver side block drain at the same height. Any chance the knock sensor is screwed into a coolant passage? The engine cooling section of the factory service manual has been about useless for this project.

**JaycenK** · 08-23-2010, 05:01 PM

Yes that is the other coolant passage. Almost all Gm 305 327 and 350 blocks are the exact same except for bore and sometimes main sizes.

**pajeff02** · 08-23-2010, 06:05 PM

Originally Posted by JaycenK

Yes that is the other coolant passage. Almost all Gm 305 327 and 350 blocks are the exact same except for bore and sometimes main sizes.

Thank you! I looked it over again tonight and it is positioned just right to be in the coolant passage. Just thought it was odd to have knock sensor installed in the hole. I'll pull it tomorrow evening to finish the coolant flush.

**Firebirdjones** · 08-23-2010, 07:22 PM

Jay is correct. GM stuck the knock sensor over there throughout the 80's and into the early 90's on computer controlled cars with electronic controlled quadrajets or TBI's as well as Tuned Ports.
Right up until they redesigned it and introduced LT1 in 92.

If you remove it,,,and my memory serves me,,,there is a specific torque rating for those when you reinstall. And if I remember right, they work off different frequencies for various applications (305, 350 etc...) and should be application specific if you ever have to replace it.

**pajeff02** · 08-24-2010, 03:46 AM

Originally Posted by Firebirdjones

Jay is correct. GM stuck the knock sensor over there throughout the 80's and into the early 90's on computer controlled cars with electronic controlled quadrajets or TBI's as well as Tuned Ports.
Right up until they redesigned it and introduced LT1 in 92.

If you remove it,,,and my memory serves me,,,there is a specific torque rating for those when you reinstall. And if I remember right, they work off different frequencies for various applications (305, 350 etc...) and should be application specific if you ever have to replace it.

I have a set of factory books, so I'll make sure to check the torque spec. Thanks!

**pajeff02** · 08-24-2010, 06:28 PM

Here's the knock sensor that was installed in the passenger side block drain. Fortunately, the wire harness wasn't all crispy and came off easily. The sensor was in pretty tight but broke free after a couple of tugs on the ratchet without any apparent damag.

**JaycenK** · 08-25-2010, 06:57 AM

Lt1 knock sensors are in the same spot. Lt1 blocks are different from gen 1's but dementions and exterior of the blocks are the same except for one more motor mount bolt hole while they still retain standard gen1 motor mount bolt hole locations as well. I know there is an extra bolt hole on the driver side of an LT1 and there may be one on the passenger as well. Good luck with it.