Thermal contraction of aluminum. Stuck Vintage Cadillac Alum. Distributor in Iron Block 1

[cadchris]

Gentleman,

I am trying to assist the vintage Cadillac community that has a chronic problem and chose the metallurgy section first of this board and will also post the same in the corrosion section.

Vintage Cadillac's of certain years used cast aluminum distributor housings and most of those are seized and stuck in the iron block distributor bores due to most likely galvanic corrosion.

Many have utilized most of the penetrating oils on the market without success only to end up snapping off the distributor housing utilizing available mechanical means to free the distributor...BFH. I have come up with a few different methods for others to try, and one involves super-chilling the distributor shaft outer housing either with liquid CO2 or 134a Refrigerant Freon in an attempt to thermally contract the aluminum from the iron block bore. There are some penetrating oils on the market that do combine an oil with a spray which claims to super-cool an object to -60F to break the corrosional bond or possible galling between these to metals.

Would cast aluminum contract enough from the cast iron bore to break the corrosion bond at -60F or would the temperature need to be far below that point?

These Cadillac cast iron motors were also know to have a high nickel content.

Can anyone calculate this contraction of aluminum or expansion of the iron?
Are we talking about thousands of an inch or greater?

I also thought about if the distributor could be packed in Dry Ice in an attempt to reach -109F for more thermal contraction of the aluminum.

Would heating the iron block to operating temps of 190F or possibly 225F be enough to expand the iron bore while attempting to super-cool the aluminum distributor housing shaft in a further attempt to break this bond?

In addition to the thermal effects on these metals, my idea would be to apply a twisting motion with a pipe wrench attached to the distributor housing and mechanical impacts with an air hammer into the distributor base in an attempt to create some form of harmonic vibration to further break this bond?

I also suggested continuous application of penetrating oil in hopes it will wick down to the target area.

The following link depicts the subject distributor and apparently, the corrosion occurs below the collar on the 2nd shaft bore alignment ring where it sits in the block bore.
Link

Your thoughts are greatly appreciated an explanation a remedial level!

Thank you,
Regards,
Chris

 

[OGMetEngr]

This sounds like a fun problem (maybe not for the guy with the caddy though).

Since I don't have the dimensions of the alignment ring or the exact coefficients of volumetric expansion in front of me, I'll have to make some general assumptions. I'll assume the ring is .8" radius and .8" tall for the sake of simplicity, and I'll use coefficients of volumetric expansion for aluminum (generic) and iron.

If both materials were brought down to -109F using dry ice, the difference in measurement of radius between the two would be in the range of .036" (since aluminum will contract roughly double that of iron). This is assuming both materials are at equilibrium dimensions (i.e. - not a press fit).

As for using the penetrating oil, I'm not sure if that would be enough removal of heat to make that much of a difference. It would be worth a try if the dry ice route is that much more involved.

The heating the engine block while cooling the distributor doesn't sound like such a great idea. Sounds like a perfect way to crack a block.

 

[cadchris]

Thank you "Old G"! Did I understand your name correctly (OG)? Or, please pardon my assumption!


Yes, from what I've read, a lot of guys do have fun trying to remove these corroded stuck distributors. I think one guy literally lifted his motor out with an engine lift chained to the distributor!

Thank you very much for your advice. I really appreciate it. I was just trying to figure out a way to get the most clearance as possible to break the corrosional bond and expand the iron block bore and contract the the aluminum distributor shaft housing in a logical and safe manner since the end result for these CADILLAC Owners are broken distributor housings when trying to remove them.

Can you visualize this problem of the aluminum distributor being stuck in the iron engine blocks 2nd alignment support bore?

Just so I can understand correctly of the thermal expansion and contraction characteristics of these metals in their specific locations because I'm confused about the iron block bore:

#1. On a hot or warm iron block; the support bore diameter that surrounds the distributor will expand and the bore will get larger; also, the same bore would get smaller if chilled.....?

#2. The cast aluminum distributor shaft housing will contract when super-cooled and expand when heated....?

Is the rate of contraction the same for Aluminum vs. Iron linear thoughout the span of temps. or only at the given temp of -109F?

Because, -109F maybe difficult to achieve depending on the availability of dry ice vs. a CO2 spray or 134a Refrigerant/Freon used as a cryo-spray which I believe are both in the range of -60F, but I have an e-mail to confirm the open air temps of 134a.

Here's another concern, I'm not sure if I'm interpreting this correctly from the following source who specializes in embrittlement testing:
Link

I'm concerned with subsection (a). Is there a risk of cracking this cast aluminum from super-cooing the housing ranging from -60F - -109F to where it affects the micro-structure of the cast aluminum and if a mechanical twisting force or impact is applied while at that sub-cooled temperature or when even returning to ambient temps.?

Further, I have also been reading about cryogenically treated aluminum.

Pg. 4 section #4.
"How Aluminum Alloys Can Fail Us:"
Heat Treatment Damage: Can take the form of improper solution heat treat temperatures resulting in:
a) under soak from low temperatures low mechanical properties or

b) excessive temperatures resulting in eutectic melting within the aluminum microstructure. Heat treat damage can also happen from improper artificial aging temperatures and times, resulting in lower mechanical properties also.


The area in question with a corrosional bond is the middle bore ring as depicted in the link above in my first post, and there is no way to directly freeze that area or apply direct heat which is why I thought about both super-cooling to "cold soak" that distributor when the iron block is "heat-soaked" to normal operating temps.

Funny thing is that this specific forum member who brought this topic up once again lives in Finland where the temps get down to -50F. I told him wait until winter and this distributor might just pop out like a Popsicle! But that's just an assumption.

However, other Cadillac owners are looking for some methodical procedure for this chronic problem working at "normal ambient temps".

I'm just putting a lot of thought into this project before I give any further advice.

Not knowing metallurgy, I wondering if the super-cooled aluminum micro-structure will shatter when applying force. Is this possible?

This situation sort of reminds me of a procedure to Cryogenically treat brake rotors but I assume this procedure would not be a form of tempering non-ferrous metal.

Any ideas and your expert advice once again will be greatly appreciated for the vintage Cadillac Community.

Regards,
Chris

 

[swall]

I would start with thermal cycling. Heat the block around the distributor and let it cool. Repeat maybe a dozen times. I think I would shoot for a temperature around 400F. If no progress is made, then I'd go with the heating of the iron and freezing of the aluminum. Repeat this multiple times as well. Look to see if you can get a puller on the distributor or make something so you can tension it while doing the heat-freeze cycle.

 

[redpicker]

Please do not use R134a spray to cool the distributor. Not only is this illeagal, it is harmful to the environment. While I am not an environmental activist, I to try not to harm the environment when it is not necessary, and this is definitely a situation where it is not necessary.

I think swall's idea sounds the best. Repeated heating/cooling cycles. 400F sounds high, but not too high. If you have an acetylene torch, you can heat the iron block with a rosebud and monitor the iron temperature with a 350F tempil stick (you should be able to get one of these at a welding supply shop). Don't try to remove the housing while it is hot; but let it air cool to room temperature (yeah, let it cool overnight). I'd try at least two heat cool cycles before I tried to pull it out. You want the uneven expansion/contraction to break the corrosion products. Do not use water to cool, as part of the point is to drive all the water our of the corrosion products. If, after a couple of cycles, you could trying filling the distributor housing with dry ice (while the iron is hot) as the aluminum will also conduct heat (cold) very well.

Good Luck,

rp

 

[1gibson]

If you need a quick cooling spray, take a can of compressed air and spray it upside down.

I think you need to design a specialty puller that can hold tension, while you heat/cool/whatever.

 

[EdStainless]

When you heat the entire assembly the Al will expand more than the CI, the hope is that you will actually crush the Al slightly thereby creating some clearance.
Cooling will create clearance by the Al contracting more than the iron.

Do you know how these were assembled originally? What the distributor simply placed in, or was it a press fit, or were they cooled before insertion?

At low temps thermal expansion is not linear. But you can be assured that it will be far lower than that of a Ni CI.

I would go with repeated cooling cycles and applications of a good penetrating oil. Applying slight rotational force would be helpful also. You need to break down the layer of corrosion before you have a chance to remove it.

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[dgallup]

Which Caddy engine is it?

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[Compositepro]

Redpicker, 134A is is used in freeze sprays and cans of dust-off, so it is not illegal. However, when two parts are tightly stuck together like this it is very difficult to get the temperature to be much different between the two. I do not believe that thermal cycling will be very effective. Heating can be useful to dry out any moisture (heat to above 220F, 180F will do almost nothing for drying in a closed cavity). This will allow penetrant to soak the corrosion products.

The corrosion products are like concrete. They are brittle and vibration can break them-up. This problem is very similar to freeing a frozen nut on a bolt. First break the bond to get a little movement then reverse to get a little more movement each time. This slowly grinds-up the corrosion products into small particles that can be floated away by the penetrant.

Again, reversing the load direction for each "blow" is the key to loosening parts. Repetetive blows in one direction will lock the corrosion products tighter until the parts break.

 

[OGMetEngr]

I don't know what specific aluminum alloy this is, but all I've worked with have pretty low impact resistance at all temperatures (including low temperature). If the cooling approach is used, be careful impacting the distributor as it can break easily. Heat cycling may work, but 400F is pretty high and has a possibility of warping the block. Trying to cool the aluminum while heating the block won't work as aluminum is just too conductive.

I would first cool the distributor and block a low as you can, while thoroughly soaking the area with penetrating oil. The extra clearance at low temperature should allow the penetrant to soak in. Be careful using impact forces on aluminum as it has low impact strength. Twisting or better yet steadily prying the distributor up may work the best. Do this cooling cycling and penetrating oil application a few times before you give up.

As temperature drops, Al will increase in strength slightly and ductility will decrease slightly. The microstructure remains essentially unchanged at low temps (Al is a material used for cryogenic temperature equipment). The statements you give above are referring to heat treating at too low or too high a temperature (both of which are much above room temperature).

Most importantly, check back in and let us know what you did and what worked/didn't work.

OG stands for Oil & Gas, but you could refer to me as "Original Gangsta" if you want to ;P I worked on cars for a few years before and while going back for a degree, so I can definitely relate to this problem.

 

[cadchris]

Many Thanks; to everyone who has shown interest in this subject in helping to solve a very old problem within the Cadillac Community at a "Metallurgical Level"!

"OG": now you definitely need one of these old Caddy's......thanks for your informative post. I'm now concerned with twisting when cold or how cold is too cold in the realm of "ductility will decrease slightly" when cold??????

To answer a few of the posters questions:

--The subject vehicle is a 1969 Cadillac DeVille with a 472 motor. The 472/500 were basically the same block in addition to the 425 / 368 engines used from that era and were said to have unusually high nickle content in the cast iron block. It was also confirmed that the Cadillac engines timing was so stable the distributor was never adjusted from the factory setting, (I guess due to "metallurgy" and mfg. of the components back then); timing chain, camshaft, and distributor durability. This made the engine so reliable, that it has been rumored that the distributor would go undisturbed for adjustment 20-30-40+ yrs. unlike a Chevy engine that needs timing checked and adjusted more often where the distributor is rotated for these manual adjustments and therefore kept free.

But I still believe there is some form of unique galvanic corrosion or other type of corrosion occurring in this area for how wide-spread the problem is.

--The distributor is only dropped in and not pressed and is not mounted vertically but at an angle....see photos in links below.

#1...Would the use of an Non-contact I.R. Thermometer be sufficient to measure temps vs. the "TempilStick" if not easily obtainable?

#2...From my understanding; is to slowly heat the iron block area around the distributor during the 1st phase then allow to cool down, and then heat the cast aluminum distributor shaft during the 2nd phase and cool down....correct?

#3...For further confirmation, what target temps would be recommended for the iron block and for this unknown type of cast aluminum alloy distributor of 45 yrs. old?

#4....EdStainless : You mention the abbreviated text of "CI" and "CINi" does that stand for Corrosion Inhibitor? Ni indicates Nickle Alloy?

Compositepro : I'm glad to see you are a (CE) so hopefully you can address the following about refrigerants. I'm seeing conflicting info in product specs for 134a. I did get an e-mail back from National Refrig. and they said their F3CCH2F (R134-a) has a boiling point of -15F.
("The boiling point is the temperature you will get when discharging liquid refrigerant onto a part at atmospheric pressure) .

I've seen other indications of freeze sprays with the MSDS containing R134a indicating -60F. Unless they are withholding some other component in that MSDS to reach -60F or, unless its marketing hype... But it makes me wonder........

This same Tech. from National Refrigerants also mentioned the Liquid Nitrogen route, but he said you guys wouldn't be too happy about how brittle it would make the iron or aluminum and was one of my original concerns utilizing the Freeze Sprays, 134a, or Dry Ice which are considerably high temps., and as OGMetEngr aka "OG" states in his post, my concern is the cast aluminum alloy becoming brittle at a certain "superchilled" temps!

I'm just looking for a safe target temp above using Liquid Nitrogen which would not be a easy option. Dry Ice would be the lower limit at -109F and would be easily obtainable commercially or by discharging liquid CO2 in a fabric bag (Youtube: How to make Dry Ice) or from a CO2 Fire Extinguisher and use the dry ice powder to pack the distributor.

#5...The upper limit would be either 134a at -15 F. or is there some gas in between -15 F. to -109 F. to where this cast aluminum would be more stable against impact or rotational forces?

We'll scratch off using R12 (-22 F.) and R22 (-41 F.) for enviro reasons.....I cringe of how much a blew off in the air way back in the ol' days.

So I guess its either:
- Dry Ice -109 F.
- or similar Freeze Spray like DustOff :1,1-Difluoroethane 152a Boiling Point -15 F.

#6...Which above temps would make the cast Aluminum less brittle?

I guess what I'm asking of you guys is difficult since I'm unable to i.d. the exact type of aluminum alloy this distributor was originally casted in but the consensus among the Cadillac Community would be "they don't make'em like they used to". Cadillac apparently used the best technology of the day including high nickle content in the iron blocks which makes them have the reputation of being indestructible and highly sought after for a cheep and reliable high horsepower-torque engine and is often transplanted into trucks, boats and other cars. But the aluminum may not have been very strong nor needed to be for the mfg. of that component.


I've also attached a photo of what happens like what "OG" states. This individual somehow was able to attach an air impact wrench to the distributor, and most likely applied rotational forces in only 1 direction at ambient temps. just like "Compositepro" stated not to do and as you can see in the photo, the casted aluminum shaft is fairly thick....... I hope I know how to insert an image.....

Taken from this forum: Link

Some have tried to use a large pipe wrench, strap band wrench, and hammering on the aluminum body tabs to apply rotational force but probably only in one direction. I kind of threw many of those techniques together with my own ideas that have gone untested but seem logical since many here have also confirmed my thoughts.

But here is 1 ingenious tool one individual made he calls the "Twist-O-Matic (TM)"!
There's a few photos and some good humor here too.
Link

In addition, here are some other photos of the Cadillac 472/500 and distributor location:
Link

Link

Another thought I had was to use either Plumbers Putty or some other solvent/oil resistant putty or even JB Weld 2 part epoxy and form a "well or reservoir" to mold around the distributor base but on the iron block in order and keep it filled with different types of penetrating oil to bath the distributor shaft base in oil throughout the hot/cold soak procedures and/or driving conditions for a few weeks in an attempt that the oil will wick into the bore from thermal cycling.

Finally, if anyone is more interested about this legendary Cadillac motor, with a reputation of stuck distributors, here is a 17 min TV show about the history of the vintage Cadillac 500/472 engine performance build-up:
Link


Once again, a big thanks to everyone, and your valued time and expert advice are greatly appreciated.

Regards,
Chris

 

[swall]

Cadchris--you keep mentioning the nickel content of the cast iron block. This has no bearing on your problem. Nickel is added to cast iron, along with other ladle additions like chrome and moly and sometimes copper. The alloy additions allow a 30,000 psi or 35,000 psi tensile to be achieved compared to the base line iron. The alloy additions help promote a fine pearlitic structure and if I recall correctly, nickel additions offset the tendancy to form iron carbides that the chrome and moly might cause in thin sections. GM also operated a number of aluminum foundries at the time and probably cast the distributors in house rather than farming them out. In addition to the commonplace 380 alloy, GM had a couple of 380 variants in use. In looking at the spectrum of aluminum casting alloys, 380 is kind of in the middle when it comes to corrosion resistance. So, after 40+ years, one could expect some corrosion.

 

[EdStainless]

Sorry, CI is just short hand for cast iron, and Ni cast iron.
The Ni CI is slightly stronger, has uniform properties in thin and thick sections, and better toughness than un-alloyed CI.
Most of these cast Al alloys will get brittle when cold. They are still strong so you can try to turn it while cold, but don't use impact.
I would go with dry ice for chilling, easy enough to pack the ID of the distributor with chips and get if good and cold. Yes you will need to keep adding penetrating oil during the process.

This is the basic block design that survives as Mercury Marine racing engine. They have modified it quite a bit. They build it up to 1325HP, quite an outboard.

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[dgallup]

Well, it's quite a boat motor but not an outboard boat motor!

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[Tmoose]

In your picture it looks like it is the upper most band that is corroded.
That suggests Multiple, extended exposures to PB Blaster or Kroil are probably of some benefit.
There is a widely circulated internet story that ATF and acetone was pretty effective at helping to free up a particular type of rusted joint.

http://www.jalopyjournal.com/forum/showthread.php?t=350800

Steel on steel, slight interference if i recall.

http://www.gmcmhphotos.com/photos/random-photos/p40657-penetrating-oil-test.html

The Original fit of distributor housings in blocks was an easy slip fit. I'm guessing 1-4 thousandths diametral clearance. If its stuck I'm guessing portions of the gap is likely just full of corrosion.

If the corrosion in the interface is rusted iron, it is less dense (greater volume) as rust than when it was iron. I think that is one of the mechanisms behind rust seized parts. The rust is also kind of brittle, so heating the distributor body expands the inner part which swells up and crushes the rust matrix, helping to weaken the matrix in the interstitial spaces. Heating the iron block enough to achieve much expansion and clearance is a tall order. Heating a volume restrained by a large cool hunk of iron results in a smaller hole, and the rust crushing effect that I think helps anyway.
I've had pretty good luck heating stuck bolts, etc, then gently attempting loosening, even while hot.

If the distributor is electrically disconnected from the block (EXtremely unlikely, miraculous, since cars with points ignition work pretty reliably with no dedicated ground) a battery charger could be hooked up to reverse the corrosion process.

http://www.youtube.com/watch?v=-8vT2mdXBs8

 

[EdStainless]

Yes, outboards. They put a pair of these 1325's on a cigarette boat. Twin turbos and a the whole list of upgrades.

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[dgallup]

Cigarette boats are not outboards. They use outdrives. The engines do not turn with the steering wheel. Sorry for being pedantic.

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[mrfailure]

Regarding impact to break the distributor: I would be concerned about the possibility of impact energy transmitting to the engine block and also cracking it - cast iron also has a low impact strength.

Also, at the risk of stating the obvious, I have to believe this issue became apparent to Cadillac back in the day when they made this engine. Has anybody checked to see if GM issued a technical service bulletin on this issue? Or perhaps gone to an old-time Caddy dealer to see how their mechanics dealt with it?

Aaron Tanzer

http://www.lehightesting.com

 

[1gibson]

The acetone mixed with trans fluid that was mentioned earlier sounds interesting. Got me thinking, what is the composition of the corrosion product, and what is it soluble in? Maybe the trick is just re-saturating the solid corrosion product into a liquid/gel.

Is it mostly rust? What about naval jelly mixed with acetone to reduce viscosity enough to penetrate? As you know, most ME's hate chemistry so don't go mixing it up unless someone with a chemical background thinks it would be safe (or might work.)

 

[EdStainless]

The corrosion products will mostly be Al oxides.
While in theory you can re-dissolve them in high pH (think lye) this would also cause corrosion of the cast iron.
Trying to get mechanical breakage of the crud may be the safest route.

dgallup, must have been a racing class thing. The standard 1325 is a sterndrive, but they were actually building a pair as outboards. Either way 550 cu in is crazy big.

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