I know I'm coming in late on this, but here goes...

What is the debate here? I'm not sure I understand the part where SpitfireS talks about the valve "decelerating." Of course the valve won't magically decelerate. I always thought the argument was that at a high enough RPM, the camshaft is spinning so fast that it is forcing the valve down before it can come all the way up and seat. The combined, opposing forces of the rocker pushing down and the valve coming up is more that the retainer was meant to handle.

If the OP agrees that, at some point, valves DO float (causing bent valves during an extreme over-rev situation), I don't see why the situation described above is so implausible. To me the two (bent valves and cracked retainers) seem to be symptoms of different degrees of the same problem. Even SpitfireS' explanation of how retainers crack suggests the cam spinning too fast for the valve springs to keep up. In either situation, retainers crack as a result of the valvesprings' in ability to keep up with the rotational speed of the camshaft.

 

What's scary about it? 5350 rpm is pretty high. The valves are going to float eventually. Is 18% enough margin? If it isn't, what is?
[/quote]


Eventually yes, Honda gave us AP1 guys a 9k limit. I dont know enough about the physics in those given margins to comment, I have only read that valve float is a bad thing. My understanding is that valve float is something we dont want and if it starts happening around 5350/9000 then I would definitely love to gain more understanding ,indepth, of such mechanics.

 

What's scary about it? 5350 rpm is pretty high. The valves are going to float eventually. Is 18% enough margin? If it isn't, what is?
[/quote]


Eventually yes, Honda gave us AP1 guys a 9k limit. I dont know enough about the physics in those given margins to comment, I have only read that valve float is a bad thing. My understanding is that valve float is something we dont want and if it starts happening around 5350/9000 then I would definitely love to gain more understanding ,indepth, of such mechanics.
[/quote]

5350 RPM at the camshaft = 10,700 RPM at the crankshaft, right (2 turns of crank for every turn of the cam)? I thought this was the perceived point at which retainers would start to crack due to the valves floating and the "cam hammering" effect described by Billman. You're correct that floating valves are not good, but 10,700 RPM is well above the intended limit for the motor (8,900-9,000 RPM). I believe the general solution for valve float is strengthening of the valvetrain (stiffer valve springs, lighter valves, cams/rockers/retainers strong enough for the stiffer springs).

 

What's scary about it? 5350 rpm is pretty high. The valves are going to float eventually. Is 18% enough margin? If it isn't, what is?
[/quote]


Eventually yes, Honda gave us AP1 guys a 9k limit. I dont know enough about the physics in those given margins to comment, I have only read that valve float is a bad thing. My understanding is that valve float is something we dont want and if it starts happening around 5350/9000 then I would definitely love to gain more understanding ,indepth, of such mechanics.
[/quote]

5350 RPM at the camshaft = 10,700 RPM at the crankshaft, right (2 turns of crank for every turn of the cam)? I thought this was the perceived point at which retainers would start to crack due to the valves floating and the "cam hammering" effect described by Billman. You're correct that floating valves are not good, but 10,700 RPM is well above the intended limit for the motor (8,900-9,000 RPM). I believe the general solution for valve float is strengthening of the valvetrain (stiffer valve springs, lighter valves, cams/rockers/retainers strong enough for the stiffer springs).
[/quote]


Ahh that makes more sensr, I was assuming general RPM at the tach would see it. Now having it explained to me its the camshaft speed youre refering to Im putting in Ferrea Comp Plus valves and BC Dual springs with steel retainers... I feel this is a great margin of safety as I intend to keep the 9k redline... or maybe 9.2k

http://www.youtube.com/watch?v=_REQ1PUM0rY

 

Can the s2000 valvetrain handle stiffer valve springs? I've heard things about other systems having trouble over time (increase wear on valvetrain, worn cams, etc.), but having never dealt with it personally, I have no idea. Man, I need to get some money so I can stop BSing at get my hands dirty with the s2k lol

[EDIT] if you're keeping the same revlimit, why change out the valves/springs? Just maintenance (decreased spring tension over time)? Also, I didn't mention the 5350 RPM initially, but I believe crankshaft RPM/2 = camshaft RPM

 

I'd also like to add - the "cam hammering" effect Billman references is not a novel concept. It is referred to and upheld in other enthusiast communities. I knew it sounded familiar, and some research reveals this effect is believed to be responsible for broken rocker arms in the BMW M20 engine. Broken rocker arms could not be caused by valves slamming shut. I know it might seem like an apples to oranges comparison, but the systems are similar.

 

To have alittle more margin of safety over all. I have never mis shifted nor do I plan to, but its all for alittle extra safety. I have spoken with many builders and they told me not to worry about the stiffer springs. The BC springs were the best balance IMO OEM is 64lbs one source told me while BC states their springs are 84lbs seat. I dont drive hard often so no worries unless somelike like bill or my builder says otherwise.

Is cam wear real? I didnt think it was significant with roller rockers?

 

Is cam wear real? I didnt think it was significant with roller rockers?
[/quote]

It probably isn't an issue for the camshaft. Roller rockers are there to reduce friction and keep the rocker in contact with the cam lobe (ironically, what's been discussed as failing to happen). As far as I can see, stiffer valve springs would put more stress on retainers and rocker arms, but I haven't heard about any issues with the OEM s2000 rocker arms. I wouldn't worry about it; I haven't heard about any issues with quality springs/retainers for our motors. I was more looking to add to my general knowledge

[EDIT] Yes, particularly without roller rockers, the cams and rockers do wear. I think roller rockers greatly (or effectively, completely) reduce cam wear. I could only see extremely (unnecessarily) stiff springs creating issues. Again, I could be wrong.

 

^ Ah yes, the retainer! I know know the specifics with BCs steel retainers but their Titanium ones seem to have held up 30k something miles on other guys I have asked about it who had them installed. My game plan will be inline for regular inspections, mainly just from above to make sure nothign is walking but I seriously dont anticipate that happening. Only if I do something stupid like a mechanical over rev. Im no valve retainer or honda engineer... but BC seems to swear by them and I personally dont know enough to say that an extra 20lbs is significant...

One engine builder, who suggested the dual springs, said that yes the OEM pressure may be 64lbs but you have to subtract that boost from that number, so if im running 10lbs then the oem seat is now 54 lbs under full boost? Oh well, I have a good circle of good builders to advise me in keeping things reliable.. and reliable and fast is not cheap lemme tell ya!

I wish someone had actual publications from honda listing OEM spring pressures open and closed and associated height.

 

This whole debate definitely makes my question a build, had a local guy in AZ made a motor and he had a full supertech valvetrain and he broke a valve... not sure on the specifics or how, but he did say that a valve snapped off the stem.