any more news on this guys?
Yeah it's been a while since our last update.
Anyway, we eventually got the 1.3:1 rockers and installed them. We did some runs with them on the street and based on the logged data lost a bit of power compared to the 1.5:1 rockers, even after we adjusted the timing.
While we were doing some more testing with them we had some nasty engine problems too. We pulled one valve through the aluminium retainers and almost pulled another one too, the valve that was pulled through actually dropped completely into the cylinder. Thankfully it didn't do that much damage and the only parts needing replacement were the valve and valve guide. We put it back together with titanium retainers now though so we won't have that problem again . While we had the head off we also noticed that the steel plate dividing the 2 and 3 exhausts had vanished, apparently it had gotten soft enough to get blown out the exhaust. We replaced it with a thicker plate now.
We also built a much larger plenum to hopefully get the intake working better, but it didn't seem to help that much and it was so thin/welded poorly that it cracked open. We're going to get rid of the plenum now and are designing some rolling barrel throttle bodies that should be done next week. That's also something that could potentially be built into the head as an option.