Nitro plane engine mounting hardware: help!

[Avgas]

Hey guys, so I’m mounting my engine to the engine mount and my kit did not include the nuts and washers to secure the mounting bolts to the mount. I am having a hell of a time tracking down the mounting hardware (OS 46la), and i was wondering if I could just use hardware from a hardware store. I believe the bolts included in the kit are M3.5, but I can only get M3 or M4 at the hardware store. Is it safe to size down the bolts or should I go up in size? Going up may require resizing the holes on the actual engine itself. This also applies to the bolts holding the engine mount to the firewall. Will I need nuts at all? Puzzled why they were not included.
Any advice on this appreciated since its highly unlikely I will be able to find the correct hardware.
Thanks!

 

[olds97_lss]

Are you sure they aren't SAE 4-40 thread? Standard vs metric.

 

[Greywolf74]

I would just take one of the bolts down to ace hardware or home depot. They both have sizing tools that will allow you to properly identify the size and thread of the bolt and then you can buy the corresponding nuts and washers.

M3.5 isnt very common but if it does end up looking like they are M3.5 then you can buy the nuts HERE and the washers HERE.

 

[alfredwong2003]

If you are not in a hurry, you can get m3.5 screw set from Alexpress.com.

 

[Greywolf74]

If you are not in a hurry, you can get m3.5 screw set from Alexpress.com.

My understanding is he needs nuts and washers. He already has the screws.

 

[alfredwong2003]

They do sell them in sets as well.