[RallyBob]

*Is this really as good as it sounds?

It can be, it depends what you're striving for.

*If not, what's the catch?

Finding one. They were the middle option on 1968 Kadetts only. Base engine was 1.1, middle was 1.5, top was 1.9.

*Where would one even find a 1.5L head?

See above. Good luck!

*What would be the best guesstimate at the compression ratio doing this?

Low compression pistons were rated at 7.6:1 by Opel, but were closer to 7.1:1. A 1.5 head will bump that to about 8.8:1 or so, depending on how recessed the valves are in the seats.

*Could the compression be bumped a bit more by milling the head? If so, how much milling will yield how many points?

It again depends on the condition of the valve seats. But figure .025" will bump compression by around a half point.

*How will the 1.5L head flow compared to the 1.9L (assuming both are stock) just for a benchmark?

Since the 1.5 head has smaller valves than a 1.9 head, and has a more shrouded chamber, it does not flow as well as a 1.9. It DOES have the same sized ports, but you'd need to install bigger valves and unshroud the chamber to improve the flow to the same levels as a 1.9 head.

Keep in mind it is only a three bearing head too, as well as a 10-bolt attachment. Dont' expect miracles, if you bolt a stock 1.5 head to a 1.9 low compression block, you'll have more compression but less airflow. You'll gain mileage and throttle response, but not any power.

Bob