Hi Colin
I am heating the bolt. The nut and the thread in the nut is not a problem. Once I get them moving they come out reasonable easily.
Hoping the photo below clarifies the problem. It shows the thread quite shiny but the four centimeters above the thread , that part of the bolt that passes through the armour as quite rusty/dirty.
The rust dirt residue around the part of the bolt that passes through the armour and the rust under the head is the thing that is making it tough to get out. It just wont let the bolt turn.
Heating it expands the bolt and shrinks the hole, hopefully compressing and pulverising the rust and dirt. it also lengthens the bolt giving me a bit of a gap under the head to get some penetrant into . Those I have cooked so far show the rust/dirt burnt and blackened and good penetration of the Inox.
As soon as I get the slightest movement the bolt comes out with the small rattle gun by backwards and forwardsing for a few minutes and using plenty of penetrant.
The thread and nut are inside the engine compartment...its a continental W-670 so they are and always have been liberally lubricated by the total loss oil system radial engines have
( you know the one " it it ain't leaking oil then your oil tank is empty" ) and is a reason I am cautious about heat on that side of the bolt. I have water and fire extinguisher to hand all the time I use heat because of the real danger all that accumulated oil and grease in the engine bay will catch on fire.
I am removing the armour to clean out the engine bay, change/clean the plugs do the timing check compressions and leak by and give the W-670 a good going over. Change the rubber hoses and a couple of gaskets that are notorious leakers as well ....the engine exudes oil all over the place when I run it but doesn't smoke much past start up the rocker cover hoses are practically fossilized.
I am unsure about how many engine hours it has on it but from what I have discovered from the unit histories I think it may be close to its overhaul life of
500 hours. If it checks out OK I will continue to run the Stuart with this engine , if not I will use one of my spares and pull this one for overhaul.
So far as I can tell its the original engine from manufacture so for me there is a certain authentic sweetness in keeping it in the Tank.
Only Nine to go to get rear armour off
Photo (a) unheated bolt showing clean thread and depth of rust on shank and head. (b) heated bolt showing blackened rust/dirt and penetration of Inox.