This is why: (courtesy Slipstream444)
AP2 intake retainers (in an AP1) will survive an over-rev that will otherwise bend your exhaust valves. AP1 exhaust valve retainers generally will survive a mechanical over-rev up to the point the valves bend (replacing them at that point then becomes a given). Therefore, there is no benefit in installing heavier exhaust retainers to prevent cracking... the valves will be toast before the exhaust retainers will crack in the first place, and installing heavier retainers will just lower the point at which this happens. The OEM AP1 exhaust retainers work perfectly well - it's the intake ones that need beefing up.

Obviously this is only an issue from a mechanical over-rev, it is not caused from simply mashing your foot on the throttle pedal.

 

Alright, I'm going with that! Everyone else, you have until my stuff arrives to stop me lol Thank you.

 

People dont really lie about it, people just do not ask. You dont have to provide a list of mods to enter a class. It is expected that your car is not modded beyond said class and is the job of your competitors to present a protest if they think something is wrong. Even knowing about the retainers, 99% of autocrossers do not care and would not protest you. I thought, however, this was brought to the SEC as something that should be included as an allowed reliability mod, but have not looked it up in some time. You may just check the rulebook for it as they may have changed this, but again, most people will not care.

 

You could do AP1 retainers on both sides.

Don’t mis-shift, they will last forever.

 

Honda did update both intake and exhaust retainers on the AP1 as well.

 

Also, if you do miss-shift you will know it. Some ask - what about if a prior owner miss-shifted causing a mechanical over-rev? Well, that is why you inspect your retainers if the ap1 is new to you. I've had my current S for about 10K miles and I know my retainers are not cracked. I am not planning to change them unless I miss-shift. I plan to leave well enough alone.

 

My car 150k on original AP1 retainers. I will never change them unless I have a mis-shift event.

 

If I'm going through the trouble of removing them for inspection I'm going to change them. Previous owner claims 100k on this engine but idk. Isn't it possible for a crack to start and not be visible? Regardless if I take them out I want new ones in. If I don't ever plan on trying to get more RPM out of it then is there any reason to not go with AP2s on the intake?

 

You can inspect without removing. First time you do a VA give them a good inspection. Then, forget it unless you mechanically over rev the motor.

 

Since you can inspect them without removing them do that and if they're good just follow the previous advice. If you need to replace one or some it makes sense to me to replace both sides especially on a high mileage used car with unknown over-rev history. Years ago I bent a push rod on my 396SS engine. Of course we inspected them all...and replaced them all since the heads were off. Life is so much simpler without overhead cams and chains.

-- Chuck