I'm not changing mine unless something happens.

 

 

Good to hear, but no they don't just randomly crack, you have to get into a high mechanical over rev, but the thing that makes the ap2 a nice upgrade is that they tend to hold on to the valve stem under higher duress and rather then losing a valve in the cylinder all together, will be more apt to just bending one, which means your bottom end is saved. It's an insurance policy from a driver induced error.

 

Never heard that. Interesting. If I were driving on the track at all - I might do it. As it is, I'm leaving them alone.

 

Yes, the ap2 have a higher threashold for cracking, will hold on to the valve under more duress. The sucky thing about the ap1 is you can over rev and develop some slight cracks without losing a valve on the initial incident, but over a period of time that retainers crack will continue to grow and the valve will start to sink and eventually with what seemed like a random incident let go if you don't catch it through inspection first. The only way to know you have any cracking is if you remove the valve retainers and inspect the underside where they form the cracks, or if the cracking is severe enough to visually see the top of the valve stem disappearing into the keeper. If they get to that point it is a ticking time bomb.

 

 

there is nothing wrong with ap1 retainers, and they can last the life of any engine as long as the engine isn't over-revved. It takes a decent over-rev too, around 9700 rpms to start the damage process. If you know the history of your s2000 and it has not been over-revved then the retainers are perfectly fine to keep, if you have inspected your retainers and you are unsure of the history of the vehicle you should also be safe. If you don't know the history of the vehicle and have not inspected the retainers it is wise to do so.

 

Junky seems to be saying the only proper inspection involves removing the retainers to look at the bottom. If I went to that extent, I would probably just change them to ap2.

I've inspected mine recently from the top. I will inspect them from the top periodically - maybe every 30K miles or so. My take is that as long as all looks well from the top, no observable issues or changes, and I have no incidents, then I'm good to go.

I recall Billman addressing this somewhere here. My memory is he favors leaving well enough alone with the ap1 retainers unless you can see something happening from the top. I can see both sides of the debate, but I'm not going to mess with mine unless something happens. I will do a VA and check them from the top fairly frequently. My general rule is that if it ain't broke, best not to fix it.