That was the point I was trying to get across. Lightened flywheels IMO also have an effect on this. I'm thinking with it being lightened the crank and therefore the piston, travel faster which puts the piston at a different point within the cylinder when the plug fires. This would mean that the crank/conrod/piston will all be at a different point when max peak pressure is reached hopefully ATDC when the rod and crank is ready take the pressure that forces the piston back down on the power stroke. So lightening the flywheel in affect also kinda advances things maybe. :think



Lightened flywheels, advancers etc IMO dont have as much of a critical effect on a standard compression engine as there is more room for error. As soon as high comps are added it's getting onto another level. Yeh I know they are not that high by modern standards but it still has an effect on the ignition timing. Advancers ignite the charge sooner (direct affect on ignition timing) Lightened flywheels changes the position of the piston within the bore (indirect effect on ignition timing) So with the piston travelling faster and charge igniting sooner, wouldn't the burn/point of ignition be closer to the crown/rings. Then at what point and where's the piston when max peak pressure is reached. Then there's the extra heat that is created from higher compression. This effects the burn rate and possibly causes some pre-ignition. Add cams and your then stepping up another gear and starting to mess with the valve timing, possibly adding even more pressure, larger volume to compress into the equation. It all adds up.

I'm waffling on a bit here, kinda thinking out aloud, but do you see where I'm coming from. It's all well and good throwing parts at an engine but all these parts have a cause and effect and have to work together equally as a team. The relationship between ignition timing and valve timing along with the dynamic compression ratio often gets overlooked, especially once bigger cams are added.

Compression ratios explained - Workshop - Visordown

I'm not saying the conrod is not at fault, it seems there is a weak point there and in a tuned engine under more compression and pressures maybe becomes more critical.

LOL I just had a vision of Roger going through all this when they where building Yeti's stage 3. Finding out what works and what doesn't and how they could improve on things (I wish he would write an autobiography) I wonder how many engines where blown on the path to building it. I bet he has all the answers but it wont be easy or cheap. Next you will be sticking some carrilo rods in. :grin As T.Mon says "it's an upgrade opportunity" Sorry just trying to be a bit light-hearted towards it and find a logical reason why this has happened. You must be gutted mate.

It will be interesting to see what you find when you break the engine down. I'm hoping you can salvage a fair bit and there are some tell tale signs as to what exactly caused it.

(:-})