Its at least 25 HP per 1 increase in ratio - SO 8.0 to 1 to 10.0 to 1 is 50+ HP.

Higher compression lets you take advantage of bigger cams thus more HP.

Part thrott;e in the lower rpm ranges (vs full throttle) reduces cylinder pressure (real time compression) in those critical rpms.

So yes, this part is driver controlled.

So like in a gas tow rig engine, when in high vacuum you have lots of ignition lead, but at low vacuum, timing is pulled out. Remember back in the old days, we had something called "vacuum advance".

MT the old 598 i check at the end of each season was low 180's. There was not a sign of detonation. The new engine the builder is very comfortable with the compression as long as the engine temp and timing stay where he suggested.

Did your engine builder determine why the exhaust valve broke? In post 23 it looks like the sister chamber had some fun in the past as well. Dry to the tip exhaust so reversion shouldn't be a problem .

After a lot of discussion. It was just a part failure ss valve. We believe the the other cylinder was debris from the valve. Hard to tell but we think there was no piston contact before the failure. No bent push rods or lifter damage or rod damage.

When it broke we were cruising. About 3400 I let off the throttle to turn and go back to talk to a friend we had just passed. I new something was wrong sounded like a bad miss. I was thinking something happened the the ignition box or distributor.

Were the valves Inconel or just normal SS valves? I tried running normal valves once.... I regretted it...... Inconel only now

Old were stainless per the numbers I can find on them.

Just thinking about my earlier post it sounded like a miss. One of the first things on the dyno he was having trouble setting the timing and all of a sudden the engine just shut off. Long story short answer he had to change the pickup in the distributor it would short out and fire without movement. Of the shaft. The dyno operator and owner had never seen this before.