The International Cessna^® 170 Association

I have owned my c170a for 13 years and the aircraft sat outside for the majority of its life before I owned it. My mechanic recommended we inspect the spar blocks. We attempted to remove the wing attach bolts, and could not move them. We are working in my hanger and don't have access nor do we want to use impact wrenches as the heads of the bolts are in bad shape. Has anyone had this experience and if so how did you get the bolts out? My mechanis is afraid we may be setting ourselves for a really expensive repair.

when we took the wings off my 170B the bolts came hard but did eventually come with a drift pin and hammer to start then screwed them the rest of the way so we must have had less corrosion. I used a penetrating oil called Kano Kroil. It is the best I have found.

Yep, penetrating oil and let it soak a few days, then rotate the bolt with a wrench while tapping it out with a brass or aluminum drift should remove it. Usually when they are stuck that hard, the block is indeed found to be pretty corroded. As the block corrodes it exfoliates and grips the bolt pretty hard.
Suggestion: 1) Use all-new hardware when re-installing. 2) Beechcraft King Airs, Barons, etc. use a spcial, anti-corrosive grease/lubricant on their wing attach bolts. If I ever have mine out again, I intend to use that stuff on them.

Not sure what the King Air / Baron goop is but we put
regular old anti-seize compound on AN/MS hardware
before re-assembly.

Bela P. Havasreti
'54 C-170B N170BP

Try turning the bolts, you may want to check the condition of the small bolts that attach the blocks in the spar and remove those, to remove the blocks when you pull the wing.
I use Parker "o" lube to lubricate areas that are not subject to heat. Parts coated with that stuff pull apart years later with little if any resistance.