Heat exchangers Allen key

[kavadarci]

Hi,
I'm reading that Allen key for the heat exchangers is 88 or 100mm.
I have 1976 911 targa 2.7l.
What size is the Allen key for the heat exchangers?

Thank you.

[stormin48061]

This is what I did. i think i pulled it off of PP somewhere. I cut off a 10mm hex about 1 inch long and insert into a 10mm socket with a 6 inch extension. Works like a charm and the socket/ratchet combo gives u more leverage. Heat the nut first.

[O=O]

8mm

[jrbennett]

I use a bit from Snap-On, it is an 8mm Allen key, length of the bit is 126mm. I think you need at least 110mm.

part/tool number: FAML8E

[john walker's workshop]

Absolutely use an oxy/acet torch and heat each fastener red before trying to crack it loose or you will break studs. Mapp gas will eventually work as well, but it's slower.

[juanbenae]

Originally Posted by john walker's workshop

Absolutely use an oxy/acet torch and heat each fastener red before trying to crack it loose or you will break studs. Mapp gas will eventually work as well, but it's slower.

since john took some time to suggest a solution you really need to simply follow the instructions...

[Targalid]

The technique I used, taken from this forum, is to heat each fastener to a red heat. While it is glowing red, turn it one quarter turn then wait for it to cool and it will come off easily.

[stormin48061]

i stand corrected. went by memory and it has been a while since doing the exchangers, but nevertheless great info/advice here from the more experienced.

[Jack Stands]

A bit of anti seize on the exhaust studs also helps during reassembly if you need to remove them in the future.

[theiceman]

I was fortunate enough to take the whole side off and had it on the bench . I used standard 8mm allen key . heated cherry red and tried to remove with gloves. if it didn't move it wasn't hot enough and did it again ( same with a short 10mm wrench for the nuts ) ,. not having lots of leverage is a mechanical control that stops you snapping the studs.

My exhaust was original on a Canadian car 40 years old. Got everything out without even one break.

[kavadarci]

Thank you everyone....

I somehow thought the Allen is not a problem as much as the 10mm nut or both are pain?

[911pcars]

Heating the nut expands it, hopefully creating some separation between it and the stud threads.

Applying torque to a red hot internal hex nut might distort the hex and lose grip.

I suggest after heating the nut, spray some thread penetrant (Kroil or equivalent) on the threads so it penetrates the increased thread space. After the part cools down a bit, then apply torque.

And when that doesn't work after repeated tries:


Sherwood

[bourgeois911]

[SCadaddle]

"Applying torque to a red hot internal hex nut might distort the hex and lose grip."

That's why the guys I know that do this stuff for a living take a LARGE hammer and give the internal hex nut removal tool a FIRM whack or two to seat the tool in the cherry red hot fastener before they apply rotation to remove it.

[911pcars]

The temperature of steel heated to cherry red is about 1400ºF (790ºC), hot enough to deform the item. Let it cool a bit before attacking it with force.

Sherwood

[kavadarci]

Originally Posted by 911pcars

Heating the nut expands it, hopefully creating some separation between it and the stud threads.

Applying torque to a red hot internal hex nut might distort the hex and lose grip.

I suggest after heating the nut, spray some thread penetrant (Kroil or equivalent) on the threads so it penetrates the increased thread space. After the part cools down a bit, then apply torque.

And when that doesn't work after repeated tries:


Sherwood

What did you use to cut into the nuts?

[yelcab1]

Looks like dremmel tool

[911pcars]

Yes. A small cutoff disc in a Dremmel tool (or equiv.). Create a slot along the side of the nut deep enough to not touch the stud, then use a large flat bladed screwdriver to spread the metal to apply more penetrant and to loosen and rotate the nut. Obviously, the nuts are toast, but the long view is to remove the heat exchanger and save the studs. Breaking a stud, especially flush with the cylinder, is to be avoided, if possible.

7 out of 12. The heat-distorted barrel nut is at 10 o'clock.

When installing heat exchangers/headers, use liberal amounts of anti-seize to stave off corrosion. Periodically loosening and retightening these fasteners can't hurt either, but that requires a certain degree of anal compulsiveness assisted by fresh memories of broken exhaust stud R&R invoices.

Sherwood

[kavadarci]

I believe I'm ready for this. I have time till spring to find new (or used) heat exchangers.
Thank you.

[Guardsred911]

you can also flip a bottle of pressurize air in a can upside down to freeze it or buy a can or freeze-air (i.e. thermal shock) after you heat it. I used this with good success on this, and on the Large Oil Thermostat hoses...