How important is it to use exact OEM bolts?
 

So my IACV unit was missing 1 of the 2 bolts that holds it on. I went to the hardware store and got a similar sized one that was silver instead of gold looking and it used an Allen key instead of a 10 socket but it went right in without any resistance just like the other OEM bolt and now the unit is on there tight and secure.

but I keep reading how critical it is to properly torque bolts on the S2000 because the Aluminum and now I am paranoide. I ordered 2 new bolts from genuine Honda parts online (it was $12 freaking dollars for 2 tiny bolts!) But theoretically what can happen to my car if anything if I drive around with that 1 single non OEM bolt paired with the other OEM bolt?

Here is an image for reference:
https://cimg3.ibsrv.net/gimg/www.s2k...d2680cf4f8.jpg
The dude I bought it from was driving around for who knows how long with that 1 bolt holding the IACV unit on there. He said he drove it over 9000 miles while owning it probably with that one bolt and who knows how long it's been missing.

For mission critical parts- suspension or steering for example- I'd use the honda bolts. I know, not cheap- I about shat myself when I bought them ($$$).

The engine torque damper I have uses a longer, properly rated non Honda bolt that goes into the engine block. I have no misgivings. My coil cover bolt fell out and I used whatever non honda bolt would fit- no issues.

For the IACV, you will be fine- just properly torque it.
darcy

The bolts themselves were $2.22 (still overpriced) but standard shipping was $10 lol come on man!

I was mostly concerned because the IACV unit gets super hot after I drive the car so I didnt know if using the non exact bolt would cause issues.

As long as you're not using a stainless steel bolt, you should be OK.

FWIW, Mcmaster Carr sells JIS high strength hardware. I think they carry 1.25mm thread up to M10 size.

All the OEM bolts are C10.9. So if you buy anything lesser (C8.8 for example), you may not be able to torque to spec without damaging the bolt.

I think it is a stainless steel bolt exactly like this one:
https://cimg8.ibsrv.net/gimg/www.s2k...8261e93ffc.jpg
Why would those be bad? Sorry I am not a mechanic and don't know much about this stuff. I will only have it in there for about a week longer until the new OEM bolts arrive think any serious damage could occur in a week? I have only driven it one time.

Just a guess, galvanic corrosion.
Differences in how the metals expand when heated may not be good either, but I'm not sure.

Corrosion and the stainless hardware is much softer, they will easily snap if you torque them to much (oem spec might be enough in some cases).
If just for one week I wouldn't worry.

The torque spec of that part is very low, perhaps just under 9 ft lbs apprx if memory serves correct, so that bolt should be okay as that amount of torque isn't much more than a hand tight snug. If it was me I'd just use a normal metric hex bolt and be done with it, but if that bolt was the right length it will fine. All you are doing with that part is keeping it compressed against the manifold so the o-ring seals, no crazy amount of torque needed.

Use e-store honda and have the part delivered to your closes dealership, that way you avoid the shipping costs.

The problem is my closest Honda dealership is over an hour drive =/

I live in a state where everyone drives trucks and MERICA cars.