Drain plug on the bottom of the rad. On mine its on the passenger side tank. 9/16" wrench if I remember correctly.

 

And ALSO remove the two drain plugs (one on each side of your engine block) so you drain the coolant out of the engine block. You will be amazed on how much coolant the engine block holds AFTER you drain the radiator.

DUB

 

Those drain plugs are hidden by the spark plug looms on a '79, so you will have to remove those to get to the plugs. Also those plugs can be very difficult to remove. If they haven't been replaced with brass, I don't usually try too hard to get them out with the engine in the car. If you twist them off or damage the threads in the block, you'll be pulling the engine. "Learn from the mistakes of others...you won't live long enough to make them all yourself."

 

I wouldn't touch the 40+ yr old block drains with a ten ft pole. Not worth it.

 

I tried loosening mine. SS with teflon tape. 10 year old engine.

NOT gonna happen.

 

Well... I use a six point socket and.... to date have I never had one not come out.
They always come out....and that also includes the Allen head block plugs that some mid-years use. They come out. I have had only ONE mishap....but that still does not stop me from doing the job as it needs to be done.

The factory plugs are ferrous metal and not brass so they can handle it.....but you all can do as you wish. I do pass judgment on any of you and how you choose to do repairs on your car. SO if you want to leave them in...fine by me. And removing the spark plug wire shields are not big deal in my book.

I was just stating a fact that NOT all of the coolant is being removed unless these block drains are removed.

And not knowing if any of you work on the new Corvettes that use the Dex-Cool coolant. It is know to turn into a clay sludge type crud that sits on the bottom of the engine block. And I work on these Corvettes aslo...so I have to remove the knock sensors to do a thorough repair. And not bypass this crucial step just because they may be a bit problematic.

And I know we are not talking about Dex-Cool coolant...but it is the procedure of draining the system is what I was referring to.

DUB

 

I replaced my engine drain plugs with small 1/4 turn ball valves.
Draining my block these days is a snap.

 

Thats what I 'm terrified of: the SNAP!

 

On a slightly related note: Does anyone know the locations in the block that would be ideal for installing a knock sensor for EFI?

-If it's going to be in one of these stock coolant drain plugs, I might try it anyway.
(I'm already removing the exhaust, radiator, and top half of the engine; if I break off the plug and need to remove the block then I'll just "rip the bandaid off" and have the bottom-end rebuilt.) -I don't want to do it right now, but if I get an excuse, I'd take it.




Adam

 

I was hoping you'd say that! -I was talking to my dad yesterday and he said that some C3s had the bottom drain plug and some didn't.

-Is it worth draining the hose going from the top of the intake to the heater core, too?


Adam

 

Sounds like a partial block fill, to me - just makes the block stronger, right?


Adam

 

What kind of knock sensors does your ECM use?
The factory 1 wire or 2 wire sensors?
I hate the sensors that go into the coolant- I prefer the ones you can bolt onto the block and not have to drain coolant to replace.
Just my .02
Elm

 

That's a great question I don't know the answer to.

I know that the GM 10456288 works really well with my Holley HP ECU and I THINK it's appropriate for a stock bore engine; no idea whether it's supposed to go in coolant or bolt to the block... I didn't know those were options...

Edit: I found out I do NOT need to drain the coolant to install the knock sensor.
https://forums.holley.com/showthread...ors-Holley-EFI

Adam

 

Nice link.
Thanks!
I've been playing with the 2 wire sensors on my install but I'm not too confident they are working properly so I may go back to the 1 wire variety if I don't need to put them in coolant.

 

I know how you feel. I am not saying that I do not grit my teeth...but...

I have now gotten to the point that 'it is what it is' and I have no control over it. Much like wheel studs snapping...or thermostat housing bolts snapping off....or trailing arm pivot bolts being seized...or the fuel fitting in a Quadra-Jet that pulls threads when I am trying to change out the fuel filter.... it is all apart of the job.

Sometimes I am the windshield..and sometimes I am the bug.

YES...the block drain is where the knock sensor is installed.

Adam. I often times need to use my 1/2" 30" long breaker bar to get them to move. IF I feel that they are not wanting to budge. I use my impact and 6 point socket and ONLY squeeze the trigger to shock the plug. I am NOT trying to get it to move. I am just slowly shock the area for awhile. Then I use my breaker bar again...and darn near every time they come out. Use constant steadily increasing pressure on your breaker bar. In some rare scenarios..i will tap a bit on the trigger of my impact but only for about half a second...then tighten it...then loosen it...just shock it.


***JOKING***

YES...actually filling up the block with crap and crud makes the block have MUCH more integrity so you can build the heck out of it and push it to limits that most engines can only dream of begin able to achieve. ***END OF JOKING***

I know some people who have filled them with concrete...now that is a thought. NEVER have to worry about coolant drain plugs. And it can not be run too long either.

DUB

 

Actually, Block Filler is like a plaster paris (concrete), so to speak, and can be had from Summit. Rumor has it that circle track guys used it to get a lower center of gravity. They never had, seldom had, overheating issues. Maybe because the block was not filled to the deck, IDK how that worked..