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.

No...sorry. I hate to be like this...but...

9LB-FT doesn't sound like much between us friends. But its ~the maximum allowable torque for a M6 C10.9 fastener. For reference, 9LB-FT causes ~2800LB in clamping load, depending on thread friction.

Its PAST the max allowable for a lesser fastener grade.

Those silly O-Rings seal properly given a clamp load that some nerd figured out. That's why the screw size, type, and location is where it is.

If "use whatever" worked...then Honda could have saved some cash by using lesser grade fasteners. Almost every hex screw on the car is C10.9.

It certainly matters.


Why am I like this?

Mechanics don't realize this a lot of times either.

Stainless steel should never be used against aluminum. The corrosion reaction sacrifices the aluminium. Basically turns it into a powder.

Stainless fasteners also have a different torque/tension relationship. So the torque you put in doesn't equate to the right amount of clamping load for the joint.

A "standard grade" stainless fastener is also substantially weaker than a C10.9 steel fastener. So you CANNOT torque to C10.9 spec without stretching it out.

Use a plated C10.9 flange JIS hex screw and torque to spec. Again...McMaster carries them.

A week with the stainless bolt won't hurt, as long as you're not spraying it with a catalyst (salt water, for example).

Just wanted to take this opportunity to share this stretched bolt from my modding past. This was from a tensioner bolt after a (non-s2k) supercharger install - the extra force from the supercharger was more than the bolt was designed for and thankfully it didn't snap before it was found.

https://cimg6.ibsrv.net/gimg/www.s2k...c5b4557c09.jpg

I dont believe the IACV unit produces nearly that king of force if any =p

Ha, I know but this bolt is too neat to not share.

Like someone said for serious load bearing parts I wouldn't run a random hardware store bolt even as it could easily break and cause more damage. This is things like suspension components, brake calipers etc. That isn't to say you have to but a bolt from Honda but that is often easier than figure out what grade the OEM bolt is and then finding the same grade bolt in the size and thread pitch you need. For something like your case I think it is probably find but it is smart to replace it with the right thing sooner rather than later.

For OEM honda stuff I always look it up on hondapartsonline or a similar site and then toss the part number in Amazon, ebay and even just google to find the best overall deal after shipping.