I've heard claims that the retainers failed without an over-rev, but I remain skeptical. When the valves float, the valve train takes a beating that far excceds the forces encountered in normal operation. The valves are closing as the cam surface approaches them at a high rate of speed; The impacts are like putting the parts in a forge and pounding them, and I still haven't seen anything to convince me that they will normally fail without the hammering. Even if there are some defective retainers that fail in normal use that wouldn't make it a cronic problem that we (normally) need to worry about.

I doubt that either you or I will drive our cars any harder than Modifry drove his, but it's nice to know that I'm not the only person who's "stress testing" the OEM retainers. I have a Modifry shift beeper, and the high RPM memory will let me know if I ever over rev the engine. I've cleared the memory at 9,100 plenty of times, and on occasion I'll let the car ride the limiter during an autocross, so if revs alone will do it, I should see cracks in my retainers sooner or later.

Thanks Bill!

 

Well, if you wanted to calculate it, I'd assume you'd take the amount of pressure in the combustion chamber (150psi I think was the recommendation) and multiply that by the surface area of the valve face. Just as a rough estimate, I think the valves are around 30-32mm in diameter, which is more than an inch, so you know the surface area is greater than 1sq.inch, which means that there is more than 150lbs of force pushing on the face of the valve holding it in place.
How is that possible? Was there some sort of friction (carbon buildup or something) that was holding them in place? Or did you do it w/ the plug in while the piston was up in the compression stroke?

 

*shrug* no spark plug, it wasn't on purpose. Maybe that piston was up?

Even when the head is out of the car (well other heads I have) the valves don't just fall out, there is a little (not much) friction there.

NOT THAT I'M SUGGESTING ANYONE DO THIS!

I just did it on accident and got lucky.

 

I have pics of a head where an intended 3-4 turned into a 3-2 $hift.

I'll post them soon, but expect pics of the following when VTEC screams 12K rpm.

1) piston to valve contact
2) dropped valves
3) warped retainers

 

IMO this should be linked into (or moved to or whatever) the FAQ on top of UTH.
Great info

Edit : Update.
All my intake retainers look like this:

After resetting the high rev memory of the Modifry Shifter Beeper I went for a drive.
Once fully warmed up I let the car bounce of the rev limiter twice, in 2nd and in 3rd gear.
Both time I just kept my foot down.
The shifter beeper played back 9100 rpm.

 

*shrug* no spark plug, it wasn't on purpose. Maybe that piston was up?

Even when the head is out of the car (well other heads I have) the valves don't just fall out, there is a little (not much) friction there.

NOT THAT I'M SUGGESTING ANYONE DO THIS!

I just did it on accident and got lucky. [/QUOTE]
I've seen valve spring work done on other cars by simply rotating to TDC to hold valves in place. Don't know if you can cause damage doing it on an S2000.

 

Wow this thread is very helpful and informative and definitely a good reminder to keep an eye on retainers even if a over-rev never happened sorta like insurance. I am definitely going with AP2 retainers now and my final question would be are stock AP1 OEM springs and seats very good or are the supertech alittle better?

 

What exactly do you expect this "test" to tell you?

 

Where the rev limiter actually engages.

 

Noob here, but what kinda $$$ is one looking at for the AP2 retainers and such upgrade and install...

What all would be needed for the proper 'swap' also...