"...heat is your friend"

...I'm about to undo some 40+ yearold allen head bolts on my 280 outdrive transmission case, and would like an indication of the level of heat I should be applying to the tread zone...

Is this a useful scale?...
1...body temp
2...can touch but briefly
3...cannot touch
4...water drops evaporate quickly
5...water drops sizzle
6...things start smokin'

Just trying to give you some options, and would understand if noone wants to comit themselves as i guess its one of those grey areas in a mechanics bag of tricks, and I won't hold you liable, promise...Bazza.

I previously suggested a small propane or mapp gas torch...... No Oxy-Acet!
You will not be able to cause any damage, and it should help!


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Believe me....... I wish it was that easy..... and it usually is with the A and later transmissions.

These are socket head cap screws sitting within a socket type receptacle.

http://www.co-engineering.net/Specials.html

The thread penetration is near 7/8".
Often the bolt shank bores are filled with a whitish dry substance in addition to the threads being severely rusted.
There is no space or area for penetrating oils to enter!

In some 23 or 24 years of doing this, I found that heat gives the best results, although there are times when heat doesn't even work.
But more often than not, the slight expansion caused by the heat is just enough to allow the threads to break free!

We have nothing to lose but the cost of some propane or map gas, and a few minutes of our time.

Once we lose that hex socket, the next step is the milling machine.
The reason for milling these out is due to the very delicate shoulders directly ahead of the capscrew heads.
The heads, special washers and the soft delicate shoulders provide the water sealing.

A good machinist on a milling machine with the proper cutter, can take the heads out without even touching this delicate shoulder. He will not only take the heads out, but he will remove the entire boat shank minus enough to grab onto for the extraction later on.


Been there/done this more than once......... Unfortunately!



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I got timed out.
One more thought:

If we use heat to expand the area where thread inserts are (these are inserts..... not direct aluminum threads), we stand a much better chance of successful bolt extraction.
We may never know if heat was actually necessary or not!
But given the two possible scenarios......... I'd say that we'd best error on the side of caution!

It costs me approximately $80 each time that I've had to have these milled out!
Not to mention my behind-the-windshield time.


Suggestion:
When going back together, I use a liberal amount of Quicksilver "Perfect Seal" on the threads, the head/washer/shoulder, and at the two aluminum mating surfaces.
It's a rather messy process, but I believe that it's worth the effort!

While I may never actually hear from him, the next guy "in" will be secretly thanking me!



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Kim, no offense to you.

Unless we've had similar Volvo Penta AQ series drive experience, and for a similar duration as myself, we have not seen this severe rust/corrosion and white powdery substance as per what these will occasionally offer up!

I know that I'm asking you guys to take my word at this..... and that may require a leap of faith!
Rest assured that I'm not going to lead our members astray.... this is too dang important!

I've had my share of the difficult ones, and I've had many people bring me these transmissions only after their own failed attempts!
Had they simply applied heat on the correct areas, they may have averted this problem!


As for penetrating oils reaching into the threaded areas........ Not a chance in Hell!
But again, one would need to see the amount if rust/corrosion in order to believe this....... especially if you put your faith in penetrating oils!

Bottom line...... what have we to loose by using heat prior to any other attempts???



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...thanks for both of your input guys... I'm in no hurry so I'l being using both a long term application of a penetrant and heat, Bazza.

Barry, not all steel bearing box transmissions give us clamping collar bolt trouble. You may get lucky, and they may come loose easily without hassle. You won't know until you begin to remove them!
Much will depend on how the last guy "in" reassembled it!
If he greased or oiled the threads only, the chance of rust and corrosion will have been increased.
If he sealed these areas well with something such as Perfect Seal, you may be in luck!


But let's say that these are stubborn!
First off, the hex socket heads by design lack integrity. The outer socket head wall can become distorted easily! Once distorted, the hex key wrench will slip! If/when it slips, you're done!!!!!!


If you plan on using penetrating oil as to help free up these cap screw threads and the female thread inserts......., be prepared to give it six months or so!

If you should decide to use heat, and if they are capable of breaking free, you'll be finished in 30 to 45 minutes!


We get one shot at this! If that shot fails, you will be taking your transmission to a machine shop.

My advice would be:

1..... do not even attempt to remove the capscrew until you have applied heat to both the main gear case and the collar. You've nothing to loose...... and have everything to gain.

2..... apply more heat than you think necessary. Propane or Mapp will not allow enough heat to cause any damage.

3.... No Oxy-Acet....... unless you were to use an acetylene rich flame!!!!
An oxygen-rich flame might cause damage!


Note:
If this was an "A" or later transmission, and/or a Merc or OMC, I would not be making such a strong suggestion to you!




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...all advise noted and appreciated thanks.