Threaded holes in 427 BOSS block

[gbranham]

What are these? They appear to be entry points to the water jacket. They're on both sides, and are threaded. Optional spot for water temp senders? Just below #3 and #7 cylinders.

Thanks, guys.

Greg
200217200218

[rustyrim]

they are drain holes on each side of the block. you can put a plug or petcock in each. Water temp should be at the end of the water path near where the thermostat is.

[Mike.Bray]

Yes, drain holes. I put 1/8" pipe plugs in mine.

Even though it's a new block you want to remove those screw in freeze plugs and check/replace the O-rings to be safe. Don't ask me how I know to do that.

[gbranham]

Thanks, Mike! I'm on it!

[Mike.Bray]

The machine shop left the plugs in during vatting and damaged the O-rings so they leaked.

https://www.imagecoast.com/images/MichaelBray1/20220929155425mediumrotated.jpg

From memory they're not run of the mill Buna O-rings but are special for the application. I think the replacement ones I used were from Earl's.