69 deville w 472 exhaust?head plug. A.I.R.passage?

[airtourla]

I have a 69 de ville convertible w 472. It has plugs in the head that plugs an old A.I.R. passage (i'm not sure what that is/was) but the rear plug has come out.(its in a carb shop, tech knows little) what size is the plug? are there 2 types, one with treads on without?
Thanks for the help. I'm in Southern California Redondo Beach if anyone could recommend an old Caddy mechanic.
Thanks for any help
Sean

[Bentley]

Hi Sean,

I'm a little intimidated by the whole wrench-turning thing, so I have a mechanic do most of my work. I recommend Gordon's Auto Works in Orange, CA. They specialize in vintage cars and have been working on my '68 DeVille convertible for many years. They've become well acquainted with my car over the years, and I'm sure they can help you. You can reach them at (714) 974-2610. No web site â€" old school.

Also, as I learned from this forum, get a shop manual. You can buy one from Amazon or eBay.

Wes

[The Tassie Devil(le)]

G'day Sean,

There are a couple of holes in the ends of the heads, and there are two threaded holes, one which is 3/8" UNC, which is for the retaining bolt to hold in the AIR Fitting when the plug is at the front, then there is another larger one for the Heater Fitting.

Then the last one is for the actual AIR fitting at one end, and the plug at the other.

The AIR fitting is 17.2 mm. in diameter, and I believe one of your coins fits in there perfectly.

Plus, I think they made this hole an odd size so that people would find it difficult to simply block off.

Bruce.

[airtourla]

it's awhile but thank you
Aloha
Sean

[cadillacmike68]

What do you mean by "rear plug" To my knowledge there are no A.I.R. fittings at the back of the heads, that's all up front where it gets in the way of everything.

If you have an open hole, threaded or not in the back, it must be for something else.

Freeze plugs will do it for the un-threaded holes. about 1/2 inch. These are available in several sizes. I have a thread here on my fun when one of the plugs I had put in in 2005 literally burned out and it sounded like a leak / blown gasket. 

The threaded mounting oles should not go all the way through the heads and do not need to be pluggd.

[Cadman-iac]

That AIR passage is drilled all the way through the head from one end to the other, allowing it to be used for either side of the engine. So the hole in the rear is plugged with a small cup plug to prevent an exhaust leak.

[cadillacmike68]

That AIR passage is drilled all the way through the head from one end to the other, allowing it to be used for either side of the engine. So the hole in the rear is plugged with a small cup plug to prevent an exhaust leak.

I didn't know that. You mean to say that they drilled a foot & a half hole / tunnel through the entire length of the head? Isn't there also a connection to the exhaust ports somewhere in that tunnel?

[The Tassie Devil(le)]

What happens is that the drilled hole passes through the exhaust ports, which is the reason for plugging each end.   One with a plug, and the other with the AIR port.

In the AIR port, there is a one-way valve that stops the exhaust gas pressure from going into the Pump.

There are some very long tools used in the construction/machining of all parts of a vehicle, and the engine block/heads/crankshaft uses a lot.   It is marvelous watching the processes involved, and I could just sit there all day, just watching.

Bruce.

[Cadman-iac]

Actually that passage is straight through the solid part of the head. They then drilled into the top of each exhaust port and those intersect the main through passage.
  The main passage is about 3/8" in diameter once it's past the first inch of the ends, if I remember correctly. The ends are larger to allow for the air tube and gasket on one side, and the plug on the other side. There's a machined step on each end, so that the plug has a stopping point, or seat when it's installed.
The cross drilled holes in the exhaust ports are approximately 1/4" in diameter.
  These all will stay clear if the AIR  system is working correctly, but if any part of the system fails due to wear, or rust, or any other reason, the exhaust gases will then be forced backwards through those passages and will eventually plug up with carbon, and the only way to clear it out is to run something through them to remove the carbon.
I have a set of extra long drill bits that I used to run through the passages when I had the heads off of mine.

   Rick 


EDIT:  Here's a couple of pictures of the passages in a 472 head. The first one is looking down the main one, and I used a flashlight to make the cross drilled passage show up where it intersects. The second one is looking at the exhaust port and valve guide and you can see that extra hole in the port, that's where the fresh air is injected into the exhaust flow.
This is why when you have a failure of another part in the system that you get an exhaust leak.
Hope this helps clear up your questions.

[TJ Hopland]

Is the main part of that passage drilled or was it just a hollow part of the casting and they just drill the ends and ports?

[Cadman-iac]

Is the main part of that passage drilled or was it just a hollow part of the casting and they just drill the ends and ports?

Hi TJ,
It's drilled through completely.  I've ran a bit through it myself to clean it up, but I only used one slightly smaller than the actual passage. I didn't want to make any unnecessary or accidental changes to it.
Like I had mentioned before, I used a longer than normal drill bit, but even with that, I had to go at it from both sides. It's a 12" bit, and the passage is actually 7/16". I double checked that after I saw your question.

Rick

[cadillacmike68]

Hi TJ,
It's drilled through completely.  I've ran a bit through it myself to clean it up, but I only used one slightly smaller than the actual passage. I didn't want to make any unnecessary or accidental changes to it.
Like I had mentioned before, I used a longer than normal drill bit, but even with that, I had to go at it from both sides. It's a 12" bit, and the passage is actually 7/16". I double checked that after I saw your question.

Rick

If you used a 1/2 " bit in a 7/16 hole, you just enlarged it.

[TJ Hopland]

I think he was saying the bit was 12 inches long.   Seems like that would have to be close to half the length of the head so send it in from each end?     7/16 isn't quite big enough to get any sort of extension in there so you are stuck with long bits.   Do they make the wood paddle bits that small?   If so that would be a cheap way to scrape some crud out.

[Cadman-iac]

If you used a 1/2" bit in a 7/16 hole, you just enlarged it.

  No, I used a 7/16" bit that's 12" long. I do proofread my posts before I send them on to the forum. But I can see where it could be misunderstood, especially with the issues that have been plaguing the forum lately. Punctuation has been getting messed up a lot and it does make reading some of these tough.

   Rick

[Cadman-iac]

TJ,
I have some of those "paddle" bits in a 7/16", they're actually wood bits. I haven't ran across any extra long ones in that style yet.
That's something to consider though if you only have access to one end of the head and you can get a long enough bit.
  I used some bottle brushes on it too, to get anything that may have been missed by the drill bit. I took a piece of tubing and inserted the handle end of the brush in it and drilled a hole through the tube and put a small pin through it and the handle of the brush. That allowed me to use it in my drill to polish up the passage and get anything the drill bit might have missed.
Not that I am going to use the AIR system on it, but this just insures that there's no crap stuck in one of those holes that might get dislodged in running the engine down the road. Who knows what damage if any it possibly could cause. Just cheap insurance.

  Rick

[Cadman-iac]

 Something else that the bottle brush on the tubing extension is good for is cleaning out oil passages in the block. It beats spraying endless amounts of some sort of cleaner into them and hoping that you got everything out.

[cadillacmike68]

This is where clean fuel and proper operating temps becomes important.

[TJ Hopland]

If a brush is all you need they make those long brush sets for cleaning passages in a freshly machined engine.   I think the set I used at friends shop even had the quick connect hex shank on em to fit a drill.    I don't recall the brand but it was one of the big auto tool brands. 

[The Tassie Devil(le)]

As for long brushes, I use rifle and shot gun cleaning rods.

Bruce.

[cadillacmike68]

As for long brushes, I use rifle and shot gun cleaning rods.

Bruce.

My USGI barracks cleaning rod is over 2ft long and would work quite well.