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Tech Talk => Engine Mechanical / Electrical => Topic started by: Kyle700 on March 01, 2012, 11:11:31 AM

Title: Chevy 350 block cooling plug?
Post by: Kyle700 on March 01, 2012, 11:11:31 AM: Hey guys,
On my chvy 350 block located between the 6 and 8 cylinder, there is (was) a plug (bolt) I removed during my motor cleansing and areosol overhaul. I didn't put it back in and dont have it anymore. It screws into something already screwed into the block, it looks like a reducer. Anyone know what I am refering to. I need to know the size the bolt to go back in. I bought a 1/2", too small, 9/16"?

Thanks
Title: Re: Chevy 350 block cooling plug?
Post by: mash on it on March 01, 2012, 12:24:07 PM: sounds like temp sending unit, 3/8" PIPE plug for later heads ('87 up), 1/2" pipe plug for earlier heads (pre '86)

Daniel
Mash on it
Title: Re: Chevy 350 block cooling plug?
Post by: Kyle700 on March 01, 2012, 02:52:22 PM: Here is a pic...
Title: Re: Chevy 350 block cooling plug?
Post by: Kyle700 on March 01, 2012, 03:07:38 PM: I don't remember a sensor being removed from there. If I remeber correctly, there was a bolt there. I don't have any extra connectors that are not connected to anything. Do I need a temp sensor? Dumb question?

Thanks
Title: Re: Chevy 350 block cooling plug?
Post by: mobboss on March 01, 2012, 03:16:59 PM: its a pipe thread. i beleave its npt not sure on the size go to any decent auto parts store and they will know the size. a brass plug will work.
Title: Re: Chevy 350 block cooling plug?
Post by: crewchief22 on March 01, 2012, 06:53:49 PM: The bushing looks like the outside diameter is 3/8"npt and the piece you removed would have been 1/4"npt. If it didn't have a sensor in it, it might have just been plugged off.

Take that picture with you to a real auto parts store and you should be able to find someone that can get you what you need. ;)
Title: Chevy 350 block cooling plug?
Post by: lbhsbz on March 01, 2012, 07:11:18 PM: 1/2" pipe thead. Go get a plug at home depot....or if your local, I've got about 20 of 'em.
Title: Re: Chevy 350 block cooling plug?
Post by: Kyle700 on March 01, 2012, 09:07:20 PM: Is 1/2 pipe thread different than a 1/2" bolt, because that didn't fit.

Thanks guys for your input
Title: Re: Chevy 350 block cooling plug?
Post by: crewchief22 on March 02, 2012, 06:18:19 AM: Pipe thread IS different than bolt thread. Pipe thread is tapered and the sizing is based off of the inside diameter of the pipe, so a 1/2" pipe thread fitting is going to have an outside diameter closer to 13/16"

3/8" npt is a little over 5/8"
1/4" npt is a little over 1/2"

Hope this helps.
Title: Re: Chevy 350 block cooling plug?
Post by: GT Jets on March 02, 2012, 09:10:00 AM: Guys,

That looks like a sensing unit adapter.....Maybe like a Stewart Warner. Somebody may have hillbillied a plug/bolt in there, but it was Micky Mouse more than likely.

It will NOT be pipe thread.... :sly:

You need to pull the threaded bushing and put in an allen headed plug. GM used a square drive plug back in the day. It could be 1/2" or 3/8" like Mash on it stated earlier...

Good luck!

GT