05thumper

In a search for comments from Billman (who I respect quite a bit)...

"It is more than ok to use ap2 retainers in 9k applications

I dont use them on the exhaust side for two reasons:

-it is extremely rare for the exhaust retainers to crack.
-it will, in theory, lower the rpm it takes for the exhaust valves to float and cause piston-valve contact

You can use them on the exhaust side, but dont mis-shift. If you do, you will bend valves before splitting retainers (kinda defeats the purpose of putting them in there)

The idea of putting ap2 retainers on the intake side is to give the engine the abilty to withstand an over-rev.

IF you are 100% confident you will never mis-shift, then surely it is ok to use ap2 retainers on intake and exhaust."

But...we have seen S2ks with cracked exhaust retainers. I have fun with my car but don't drive it crazy. Will I ever miss-shit? Who knows...I did it twice with my AP2. Each time I caught it before I let the clutch all the way out. I've been more careful with my AP1.

Maybe I don't know what's best but I hope I made the right choice. Either way a replacement head is cheaper than a new engine. I mainly chose to replace all 16 because the foreign F20C motors use the new retainers for all valves, intake and exhaust.

Judith27

I've noticed that the general consensus is to replace the intake retainers with AP2 and leave the exhaust untouched.

Carbon Blue

Honda stocked all UKDM F20 motors with the new style valve retainer and part number on both the intake and exhaust side, im sure you are misconstruing billmans words. A retainer has nothing to do with the duration and lift limit of the ap1. People have been cracking the exhaust side more recently even with mild overrevs and by speaking with others cracking the exhaust side has happened many times. Just swap both sides out at the same time and be done with it, if you over rev the motor dont expect a retainer to save you from dropping a valve, think of it as cheap insurance to replace your worn out retainers. Its the spread of mis-information on this site is what freaks people out. With that being said, if you have owned an ap1 and know for a fact that it has never been overrevved I wouldnt even bother changing the stock ap1 retainers out, the stock ap1 retainers are just FINE for the life of the car as long as they have not been damaged during an misshift.

05thumper

All my retainers were fine at 103k miles, not a single crack. I still upgraded to AP2 retainers since the shop was in the head already. Peace of mind means something to me...