quote:Originally posted by PanteraDoug:quote:Originally posted by garth66:quote:The trade off is that the closed chamber heads regardless of the pistons tend to detonate quicker and probably would need to be held to 32 to 34 degrees total.
I think Doug meant to say the "open chamber heads" tend to detonate quicker. The closed chamber heads are typically less susceptible to detonation.
No. In my experience, everything given equal it took 38 total to make the open chamber heads detonate and 32 on the closed chamber. 93 octane.
In addition, the curve on the closed chamber heads needed to be slowed down so it wouldn't be all in until 5000 engine rpm.
The open chamber was slowed also but was all in at about 3100rpm.
This is oppesed to my Boss quench heads and TRW pop up pistons running on Sunoco 260 that was all in by about 2,200rpm, 36 total, and if the city was going to bring back trollie trains, they would have hired me in that car to cut the grooves in the roads with the tires!
Those are my experiences and I do not claim to be the authority on this at all so there will be no pissing match challenges here by me.
I think Doug would be pretty right on this one.
Open chamber heads and domed pistons will create a crescent shaped combustion volume at TDC. That would require more time for combustion to propagate to the edges of the crescent shape therefore requiring and benefiting from more total ignition advance.
Quench chambers with flat top pistons will burn across the combustion volume fast. Therefore not needing and also not benefiting from more total ignition advance.
Total ignition advance is one of those things where more is not necessarily better. There is a point where excessive ignition advance even if it can be achieved without detonation will become detrimental to power production and past that point more advance will decrease power.
It has to be right for your own set up, not too much, not too little.