13.6 with 160kw (218 HP) is good but not awesome.

A 1200 that's 250 pounds weight over stock should do 13.0 with 218 NET HP (as the auto manufacturer's measure HP). The race suspension might loose .6 seconds, so that makes it good.

With 218 RWHP (as measured on a car dyno) should do 12.4 seconds. Losing more than a second could be due to the traction + gearing that is not optimal for acceleration. This is to be expected from a car not set up for the 1/4 mile.

Has Ruredi weighed his 1200? If it's lighter than my assumptions, it should be even faster.

Z-head in stock form outflows an L-head in stock form is what I've always heard. But the L-head modified can beat a Z-head modified. Is that not a true generalization?