Reply to "Water and/or methanol injection?"

I ran a "water injection" system for about 10 years, back in the last '70's and '80's. The way the system was designed to work: When the vacuum was below a set limit (adjustable), AND the RPM was above some limit (several fixed points) the windshield washer pump like pump would go on, pumping "it" thru the hoses and into the mouth of the carbs.

This was on a Datsun 510 (somewhat race prepped) with a high compression engine (10.5 - 11.0 : 1) using a "SSS" cam. This engine would run VERY strong, but under heavy load (up hill for example) the engine would begin to ping.
(Running on 92 Oct, plus the occasional booster). This engine was a 1600cc crank, 'pop-up' pistons 1800 closed chamber SSS head with opened ports generating a 200 - 220 PSI static compression and fed by dual carbs. Being "small" it would wind out to 6.5 - 7K (Um, daily - grin).

I first tried plain water. OK. Then I heard about rubbing alcohol and tried that. Finding the right mix of water/Isopropal took a while. I then tried methonal, which was an improvement. The optimal mix was about 50/50 water/meth mix. I bought the meth at a race shop. I was able to increase the timing, which increased power. I added a light on the dash to go on with the pump, so I could watch for results. If I kept the injector off, the car would ping under a known load, but when I flipped the switch, the ping went away immediately, and I could feel the power increase.
I drove this set-up during Driver's School at Sear's Point over several days. The running temp was a bit lower than without, power was up, (maybe 5-10%).
When I inspected the cylinders (by looking into the spark plug holes) The chamber was clean. I mean CLEAN!
I was concerned that the water/meth mix might take the oil off the cylinder wall, but I didn't consume oil, nor was there wear on the walls after I took it apart.
After 262,000 miles on this engine, I pulled it apart and I found that the engine was clean, with no excessive or undue wear.
I did find that my standard quality exhaust pipes rusted out a little faster.

I was also able to lean out the carbs (especially under WOT) slightly which improved normal driving gas mileage.
I believe that as the gas and "mix" hit the hot chamber, the water/meth would vaporize the gas into smaller droplets giving a more even burn, and more efficient burn.
I think I tried "Injectronic" and Sparco brands. I eventually made enough custom adjustments that it ran much better than either unit as delivered.
As for usage, I had a 1 gallon bottle, and the car had a ~14 gallon tank, under my sytle of driving both were empty about the same time. When at a track (Sear's or Laguna Seca) I would use 1 gallon of mix per 75 miles, or 4 times faster.
Due to leaning out, my overall mileage went up.
I don't feel there was any extra 'strain' or parts decay (other than the exhaust pipes).
I would consider such a system again, if available. For some reason I could no longer find such units in the mid/late 1990's.
With some tuning, and a willingness to mix a second fuel every tank, this worked well.
As for toxic ? Jeez I treated it like alcohol (Poor on the hand for that icy cold feeling! when I burned my hand on the exhaust.)
I would use it again.