Dual Port Cylinder Heads

the step would be where the cylinder meets the head. WITH step, you get much lower compression ratio. Without step, the compression ratio is higher. Assuming the combustion chamber "tub" volume is the same. It's usually in the 50-55cc range for a stock head.

Jan

On 1600 standard heads, there should be no difference in the head chamber volume, with or without the step. 50-52cc's is the VW spec. However, on the dual port 1300's, there was a volume reduction when they took out the step.

The step is to reduce "quench". Without it, the piston comes very close to the head. This caused some of the fuel to condense a bit in this area. Condensed fuel doesn't burn worth a darn, so it went right out the exhaust. The step was put in to reduce this, thus reducing emissions.

--Mike

Thanks to all for the info.