Screw in welch plugs

[Urgefor]

According to my handy dandy framing square, the deck of the block and the face of the welch plug holes are perpendicular to each other.  I couldn't help myself after tapping the oil galleries and making this small discovery and thought "Might as well tap those too."  My plan is to use the deck to bolt on a jig for the tap and machine down a chunk of aluminum bar stock I had sitting around to center the tap in relation to the hole.  Since the body of the tap is 1.499" and the hole in the block is 1.750" it makes sense to me the bar stock can be machined to match the body of the tap on one end and the block hole on the other.  Should do a very good job of centering the jig before tightening things down and switching to the tap. After that, some cutting oil and a bit of elbow grease should produce a nicely prepped hole ready for the screw in plug.

As always, I like to take into account I might not be perfect in my approach to things. If I may have overlooked something or their are other points of interest I'm not aware of, feel free to let me know.

[fekbmax]

Sounds like a plan (and alot of work) if you just enjoy spending the time doing the machining work and making up jigs.
I have threaded around 20 or so blocks for screw in core plugs simply by hand with a good quality tap and a long handled wrench with no issues. Always making sure the block was turned so the cores are level and straight, stick a bulls eye level on the butt of the tap and have at it...

[frnkeore]

Beware that the tap will have to go into the hole and up to about the 4th or 5th thread from the top. There may not be enough depth, down to the outer cyl wall to thread that far.

Your tap doesn't look like it's in very good shape. If the leading side of the teeth won't catch the skin on your finger, it's to dull and will be hard to turn, plus leave threads that can leak, if you can actually get it in far enough.

[Urgefor]

Always making sure the block was turned so the cores are level and straight, stick a bulls eye level on the butt of the tap and have at it...

Unfortunately my engine stand isn't capable of holding the block in such a way to make a bulls eye level useful. It's just a cheapo Jegs stand.   I do like the simplicity of your approach though.

Your tap doesn't look like it's in very good shape. If the leading side of the teeth won't catch the skin on your finger, it's to dull and will be hard to turn, plus leave threads that can leak, if you can actually get it in far enough.

5 of the 6 flutes seem to be in good condition on the leading edge with one being noticeably less sharp.  Thanks for the heads up on that.  Looks like I can get an Irwin tap for a reasonable price on ebay.   

[Tunnelwedge]

The tap is a NPT pipe tap that has seen better days and the plug looks like straight threads.
That's pretty much a leak.
I'm not sure this is a good plan.

[Urgefor]

The plugs are from DSC Motorsport and a new tap is on the way. According to a post Brent made back in '05 on clubcobra, 1 1/2" pipe tap is correct for the plugs.  I recall reading the same information someplace else in the not too distant past.

Dennis with DSC Motorsport said I needed to use a 1-1/2, 11.5 NPT tap.

[fekbmax]

The plugs are from DSC Motorsport and a new tap is on the way. According to a post Brent made back in '05 on clubcobra, 1 1/2" pipe tap is correct for the plugs.  I recall reading the same information someplace else in the not too distant past.

Dennis with DSC Motorsport said I needed to use a 1-1/2, 11.5 NPT tap.

Yep, the pipe tap works just fine with the DSC plugs. Last 3 or 4 sets of plugs I got came from DSC. Had been getting them from Granger but the thin plugs from them got real expensive.  I also use a good Butterfield tap and go as far as I can go with it then switch over to a old Harbor freight tap that I cut about 3/4" off of and use it as a bottoming tap of sorts. 

[Urgefor]

Sounds like a plan (and alot of work) if you just enjoy spending the time doing the machining work and making up jigs.
I have threaded around 20 or so blocks for screw in core plugs simply by hand with a good quality tap and a long handled wrench with no issues. Always making sure the block was turned so the cores are level and straight, stick a bulls eye level on the butt of the tap and have at it...

You talked me into it Keith. I took the simple approach after the new tap arrived. With an extra set of helping hands, used the good 'ol framing square against the deck to keep the tap lined up while getting it to bite and start the threads.  Turned out great.  Now I just need to get another cheapo tap to cut for a bottoming tap to use with the "shallow" holes.

Beware that the tap will have to go into the hole and up to about the 4th or 5th thread from the top.

Thank you Frank. You are $$$ with that bit of info.  That is exactly what the DSC plug needed to be flush to fit under the motor mount.

On a side note, I've searched through the forum a bit and even in my '66 Ford-n-Merc shop manual for a torque spec but didn't find anything. I'm assuming 10 or 15 ft/lbs with some good sealer would do the trick?

Edit: For future reference in case it is needed, the right rear hole (between cylinder 3 & 4) is the shallow one that will definitely require a shorter tap if you want the plug to be flush.

[mike7570]

I cringed when I saw the old paint color on your block. 🤮
It will make more hp if you change it to Ford blue 😁

[Urgefor]

I cringed when I saw the old paint color on your block. 🤮
It will make more hp if you change it to Ford blue 😁

I agree.  That is one of the main reasons it is torn down right now as noted in another thread.

The block is sound and not new to me.  I've owned it since '87 or so and it has basically become my side hobby. When time and interest (on my part) increase, I like to work on minor improvements here and there.  It is currently torn apart so I can address my son's idea of painting an engine block. He used it for his engine rebuild project when he was going through an automotive program a few years back and painted it chebby orange. Kids these days.

This is what it will look like.   

[Tunnelwedge]

On a side note, I've searched through the forum a bit and even in my '66 Ford-n-Merc shop manual for a torque spec but didn't find anything. I'm assuming 10 or 15 ft/lbs with some good sealer would do the trick?[/b]

The original screw in plugs used a NPTF thread and did not use a sealant. It creates a mechanical seal.
That's why they don't come out.
NPT threads are based on thread engagement. I would say snug with the sealant.
When I put the plugs in my Genesis block I used a Permatex sealant. It was white and gooey.