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SBC block coolant drain plugs

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Old 12-06-2017, 09:22 PM   #1
SDVette
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Default SBC block coolant drain plugs

Well it was time for a coolant flush and I decided to try to remove the block drains.... I went 1 for 2

I followed the good advise I found in searching.. Took my time.. plenty of PB blaster.. 6 point socket... no budge.. PB blaster.. stop for lunch... more PB blaster.. Finally the right side moved!

When I took out the plug, nothing came out! I looked in the hole and there was black gunk crusted. Block is a 1970 LT-1 and I'm sure these plugs haven't ever been out. Pushed a screwdriver into the hole and 47 years of gunk came gushing out! About a 1/2 gallon of coolant too.
I replaced the plug, using some anti-seize on the threads, only snug.

The left side, however, rounded off before it would move. I was pondering my options (hammering on a 14mm socket was starting to seem like a good idea) when I decided to retreat for the day, leaving this problem for the next flush.

So what so you guys suggest for a rounded-off block drain plug? Maybe heat? But how to deal with the round-off?

Thanks,
Fred
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Old 12-06-2017, 09:53 PM   #2
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Not certain PB Blaster or Kroil will help you in this location.......but continue to use and hope.

I would use a Dremel or file and square things back up and get to fit a GOOD 6-pt 14 mm socket (Snap-on quality). 1/2 inch drive and use a 14-16 inch breaker bar.

If that doesn't work, I would probably just call it quits, rather than destroy things. One of our CF members tried drilling out the plug a few years back, but went in too deep and destroyed the motor (drilled into one of the cylinders)

A few clean water block flushes should probably hold you until the engine can be removed, and the plug removed with heat and/or machine tools.

FWIW.

Larry
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Old 12-06-2017, 10:28 PM   #3
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14mm and 9/16 are virtually the same. If you can and you still want it out give it a few good blows with a hammer. Not enough to knock the side out of the block but pretty good licks. Then some of the tool companies sell a female easy out that grabs rounded bolts. That would be your best shot at this point. Or you can leave well enough alone. Yours is no different than anyone else's. They are all stopped up at the bottom.

Last edited by Robert61; 12-06-2017 at 10:37 PM.
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Old 12-06-2017, 11:53 PM   #4
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I've found a toned down impact will do the job. Even the hand held hammer driven ones like Sears sells. R - L, R - L, till it loosens.
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Old 12-07-2017, 12:25 AM   #5
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You can measure the extracted plug next to a drill bit, and attach a drill bit stop to prevent going to deep.
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Old 12-07-2017, 06:14 AM   #6
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I'm a heat and vice grips kind of guy....when you get it out consider putting petcocks in there like those used on the bottom of most radiators....that's what my 61 block had when I got the car...
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Old 12-07-2017, 09:49 AM   #7
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Drill it at your own peril!
1. It's going to be very difficult to get a drill in there, drill straight down the plug, and not roam around and get into the threads
2. If you get it drilled perfectly then how are you going to remove the remainder of the plug? If it's stuck enough that a 6 point socket rounded it off the next post will be "how do I get a broken easy out out of a block"!!!!
I've drilled many many plugs out over the years but never in the car.
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Old 12-07-2017, 10:00 AM   #8
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If you look for trouble, you'll likely find it.

Sediment that low in the block doesn't hurt anything. You might cause more problem if you break it loose and start it circulating through your radiator.
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Old 12-07-2017, 10:51 AM   #9
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The lower part of the big block holds a lot of coolant.Had to leave plugs overnight to drain completely.
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Old 12-07-2017, 11:02 AM   #10
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The suggestion in post #3 sounds like a good bet. Also suggest you replace the steel plugs with brass, and as you learned from searching use pipe joint compound and just install them "snug". The compound will prevent leaks and keep the plugs from coming loose.

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Old 12-07-2017, 11:08 AM   #11
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If you absolutely have to get it out I would go with heat. Remember that part of the block normally sees a pretty good heat cycle, so I would expect to have to use a lot of heat to make any difference. That is, enough heat to take precautions, like use an IR sensor and keep an eye on adjacent items that don't react well to getting too hot. Be sure and stay below the phase transformation temperatures of the plug or any adjacent materials.
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Old 12-07-2017, 11:26 AM   #12
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Quote:
Originally Posted by Frankie the Fink View Post
I'm a heat and vice grips kind of guy....when you get it out consider putting petcocks in there like those used on the bottom of most radiators....that's what my 61 block had when I got the car...
Thatís a great idea, but is there room with the ignition shield? I donít think so.
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Old 12-07-2017, 11:37 AM   #13
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Quote:
Originally Posted by pop23235 View Post
Thatís a great idea, but is there room with the ignition shield? I donít think so.
Good question. Haven't converted my 63 yet so can't say if the shield "boomerangs" would interfere or not
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Old 12-07-2017, 11:54 AM   #14
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Quote:
Originally Posted by pop23235 View Post
Thatís a great idea, but is there room with the ignition shield? I donít think so.
Most of the petcocks sold today are cheaply made and will break/shear at the petcock tabs (ears) attaching points. Plus the holes are too small for any debris to go thru. I would not use them.

A good, new steel or brass plug with some never-seize or teflon pipe compound is what you want.

But that is only my opinion based on 50 years experience. It will/can vary with others.

FWIW.

Larry
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Old 12-07-2017, 11:58 AM   #15
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Quote:
Originally Posted by Powershift View Post
Most of the petcocks sold today are cheaply made and will break/shear at the petcock tabs (ears) attaching points. Plus the holes are too small for any debris to go thru. I would not use them.

A good, new steel or brass plug with some never-seize or teflon pipe compound is what you want.

But that is only my opinion based on 50 years experience. It will/can vary with others.

FWIW.

Larry
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Old 12-07-2017, 12:04 PM   #16
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Quote:
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Thanks, Mike. Actually it's almost 60 years since I started working on these cars. Time passes too quickly sometimes.

Probably same for you.

Larry
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Old 12-07-2017, 12:08 PM   #17
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Quote:
Originally Posted by Powershift View Post
Most of the petcocks sold today are cheaply made and will break/shear at the petcock tabs (ears) attaching points. Plus the holes are too small for any debris to go thru. I would not use them.

A good, new steel or brass plug with some never-seize or teflon pipe compound is what you want.

But that is only my opinion based on 50 years experience. It will/can vary with others.

FWIW.

Larry
So.......rounded off plugs are much better

My '61 had the petcocks and they were fine after 10 years, worked nicely and were on the car when I sold it but...YMMV...

The petcocks I've seen FUBAR'ed are when some dweeb pounds on one ear with a hammer or tries to unscrew them with a pair of pliers clamped down on a single ear. I open up the pliers place them perpendicular to the petcock ears and put one jaw on each ear and turn....its never failed me
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Old 12-07-2017, 12:21 PM   #18
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Quote:
Originally Posted by Frankie the Fink View Post
So.......rounded off plugs are much better

My '61 had the petcocks and they were fine after 10 years, worked nicely and were on the car when I sold it but...YMMV...

The petcocks I've seen FUBAR'ed are when some dweeb pounds on one ear with a hammer or tries to unscrew them with a pair of pliers clamped down on a single ear. I open up the pliers place them perpendicular to the petcock ears and put one jaw on each ear and turn....its never failed me
Frankie:

The plug must first be removed to install the petcock. Using a new steel or brass plug(s) after this with correct sealant will probably last the car owner a lifetime..........at least another 50 years.

You are correct about the correct way to open/close..........but I use a special petcock socket for this which is even a bit better. Low cost tool (about $5).

But truthfully, the current foreign made petcocks are crap. Inline Tube makes and sells USA made that are much better, but they are not convenient to find and buy. You need to order on-line. But they are much better.

Relax.

Larry
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Old 12-07-2017, 12:26 PM   #19
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Oh - I'm relaxed...

The plugs in my 63 original block are frozen in place and, frankly, I'm trying to avoid messing with them...

I sympathize with the OP...
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Old 12-07-2017, 12:53 PM   #20
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Thanks for the suggestions guys..

For my case, I don't have ignition shielding.. The plugs were pretty easy to access.. so I may be able to get some vice grips on them.

I personally wouldn't use petcocks on the block.. that's just me.

I've been living on 'borrowed time' on this motor now for 4 years. It runs pretty well but the high CR (11:1) makes it difficult. It sat for 35 years.. When it goes I'll have to decide between finding a correct 283 block or going with a new crate motor 383 stroker.

Since I get so much info from this forum, I'll give-back a little tip that will hopefully help someone, someday.. I took a section of heater hose and cut 2 notches in one end. After loosening the radiator petcock, I slid the hose onto it, with the cut-outs lined up with the ears of the petcock, and the hose going to a container. You can open and close the petcock by turning the hose. I was able to drain the radiator without a drop getting on anything (yes, really!).

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