I was interested in knowing the options for securing nuts on bolts in areas with exposure to high heat ( like in engine compartment). There are hot forged lock nuts which have no nyloc insert, but would plain nuts with metal lock washers ( spring washers ) not serve the same purpose ? Also how effective is the method of using two plain hex nuts as jam nuts on a bolt ?

I have no clue how much a two stroke engine vibrates ( never flown an ultralight, ever ), so I am just trying to figure my options.

Thanks for suggestions.

Keith - there are a few types of nuts specific for "under the cowling" areas.  One such is https://www.aircraftspruce.com/pages/ha/nut_hex/an363.php

Another: https://www.aircraftspruce.com/pages/ha/nut_hex/ms21042.php

Or: https://www.aircraftspruce.com/catalog/hapages/ms20500.php

Of course, you can always use the time testes Castellated nut with a cotter pin.

Spring washers tend to lose their tension under heat cycles and are therefore not used.

How's the project going - sounds like you are making good progress.

Cheers,  Darrel

Darrel, nice of you to help me with that information. I am looking at AcSpruce catalog to see what I need to order.

This is mostly for non structural fittings like cable clamps and one hole straps to hold the electrical wires / fuel lines in place in the engine bay. I was using # 6 or # 8 bolts with spring washers and regular hex nut. I will probably visit the local hardware store to see if I can get #8 metal lock nuts. For the exhaust bracket I may need a An3 bolt and matching metal lock nut.

The build is making steady progress, and I am at it almost everyday. Progress is steady but nothing spectacular. Mounted the engine and exhaust and next is the prop. I will post an update shortly on my build thread.

Thanks again.