4stroke questions : Valve Float vs. Pre-Ignition, how do I find out which is which?

[icedeocampo]

I modded my engine by installing a cylinder head with bigger valves, and a bigger cylinder and piston kit.

I had an issue with valve float which sounded like pre-ignition, so asked around and somebody told me that what I was hearing was valve float and not pre-ignition.

so I resorted to the use of a valve spring with a higher tension, I think it was partially successful because I was able to reduce the weird sounds that my engine made.

Now with this setup I now hear the funny sounds after a sudden release of the throttle after WOT, or when I gradually close the throttle from WOT then I hear something like a metal to metal sound, kinda like when you strike a piece of metal with another (or like 2 drinking glasses when you do your cheers... high frequency sound, only it happens in rapid succession)

At this point I have 3 thoeries:

1. I still have valve float
2. I am now encountering pre-ignition
3. I am using a somewhat restricted flow muffler, can this be a source of this weird engine problem, should I go free flow?

can you help me sort things out...
thanks!

[tiba_karotsu]

sounds like it's detonation, try adding an extra head or cilinder base gasket to lower compression ratio & see if it will eliminate the problem or just fill up with higher octane gasoline.

valve float will not cause detonation as it will cause the cilinder to lose compression as the valves don't seat & seal properly which bleeds out pressure.