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Lycoming bolts or AN hardware

R

Rv8bill

Member
Re-assembling my IO360-B1E case halves after refurbishing. Considering using new hardware at all perimeter bolt locations. Lycoming bolt part numbers are very expensive. Is using AN hardware acceptable? What are the concerns?
 
Probably not something you want to do, BUT it is Experimental. I might have put an AN4 or two on the case flange where things are mounted. All of the tapped holes in the case are coarse thread.
 
Hopefully one of the Larry-s will join in. I've heard from more than one person that the case and sump bolts are just grade-8 automotive fasteners. I have no inside knowledge if it is true but I can assure you those fasteners are stronger than the parent material of the components they are joining. Would be fun to test the OEM component properties versus the grade-8 locally sourced ones. Maybe the OEM fasteners get some extra quality checks; maybe.

Would case fretting be less of an issue if Lyc used close tolerance bolts joining the case halves or at least removed the threads in bearing?
 
Freemasm said:
Hopefully one of the Larry-s will join in. I've heard from more than one person that the case and sump bolts are just grade-8 automotive fasteners. I have no inside knowledge if it is true but I can assure you those fasteners are stronger than the parent material of the components they are joining. Would be fun to test the OEM component properties versus the grade-8 locally sourced ones. Maybe the OEM fasteners get some extra quality checks; maybe.

Would case fretting be less of an issue if Lyc used close tolerance bolts joining the case halves or at least removed the threads in bearing?
Click to expand...

I'm not a Larry, but I believe this is correct. SAE Grade 8.

However, there was, at least for a while back, a big problem of "counterfeit" Grade 8 bolts circulating in the marketplace. They were improperly hardened and were too brittle. The problem got so bad that at my lab at NASA, we were forbidden from going out to the hardware store and bringing bolts on base. ALL hardware had to come from GSA Store-stock.

So, I don't really know the current situation, but if you go down to your local auto parts store to buy case bolts, can you trust that they meet SAE Grade 8 spec? I don't know. A source like GAHco or Aircraft Spruce presumably gets certs with their bulk orders and would be less likely to get the fake bolts.
 
Bolts

The three bolts hidden inside the sump on the four cylinder engines are drilled shank. A few other bolts are drilled head. They could be grade 8 but must have been special order.
 
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