318 low-rpm performance ........... for the NEWBE

Icetech said
I'm using trickflows on mine, with a howards roller.. CR should be 9.6:1 ish.. i might just scrap it now to find a 340 after this thread.

Nothing wrong with teens as a base to work with. Yup the open chamber heads are prone to detonation if the SCR is raised to 10:1. Now ask why? The quench of closed chamber heads provides mixture motion in the combustion chamber at TDC to aid a quick burn, to be complete before cylinder pressure and temperature rises high enough to cause any unburned air/fuel to autoignite. This can be allieviated at least to some degree by port and bowl porting on the cylinder wall side to generate swirl. You do have to exercise caution or get access to a sonic thickness tester so you do not get into the cooling system.
Another aid is water injection. Water has a pretty much infinite octane. Using this with 87 gasoline will stop detonation and reduce NOx, even with 11:1 or 12:1 CR. At low load with small throttle openings the vacuum is high. Mixture density in the cylinder is low, so the engine does not have a tendency to detonation.
All this yip yap of ICA is confusing for most hobbyists that want to build their own engine. For them I highly recommend to use David Vizard's 128 formula described in his How to Build Horsepower book or explained in a Powertec 10 youtube video. Pick the correct LSA by this method and control overlap with duration. The longer the duration, the more overlap you will have, unless you widen the LSA but you will likely forfeit performance. Use as much valve lift as you can with respect to where head flow maximises out at. Cut the piston reliefs for clearance and port the intake reliefs to aid airflow during the overlap period when intake piston to valve clearance is closest. Cut the sharp corner down on the cylinder center side to aid swirl. DV describes this in his BBC building book.