View Full Version : LT-1 drain plugs...

07-18-2007, 12:51 PM
Hi Guys,

I just got my 1993 190/LT-1 back in the water last weekend after a long winter in storage.

Both of the lower drain holes on the block, where the knock sensor on one side and the drain petcock on the other side get installed wouldn't thread for the life of me, even though the threads on the plug and sensor seemed to be okay.

I would assume (I know that I shouldn't) that the cast iron in the block would make those threads harder than the either the knock sensor threads or those on the brass drain petcock I use. This leads me to believe that it would be unlikely that there was a cross thread in these areas.

My guess is corrosion, as there was a lot of rust and scale in there. My question is what should I do ? Can these threads be tapped again ?

Any suggestions would be appreciated!

07-18-2007, 12:55 PM
i would use a thread cleaner instead of a tap.

07-18-2007, 01:37 PM
I used a plumbing tool to clean mine. It is like a small wire brush and has both a male part and a female part (make your own crude reference here). Hope that helps

07-18-2007, 09:35 PM
You can clean it up with a tap. You will need a pipe thread tap, I forget exactly which size, but a think it is 1/4"NPT.