wsa111":31j49m8q said:
......With a compression ratio in the 8.3 area you are leaving HP & torque on the table.
You need to get the cranking compression over 170# to make any kind of power.
Yes you will have to up the octane in the fuel, but if you want more power & driveability this is the way to go.
The cost:benefit for compression ratio was discussed best by David Vizard on the detonation prone Pinto 2000 engine back in 1988. Basically, it's as wsa111 and First Fox say. A moderately risky 120 thou head plane on an early 170 head with 52 cc's takes it down to 35 cc or less; no problem going from 8.4:1 with a stock 59 cc head and 22 thou gasket on a 3.3 to 12.7:1. Cost is about 120 NZ bucks for me, or two 60 thou passes. Some of the Maverick 170's were still 52 cc right up till the early 70's in the larger port heads.
Commercially, only the 215 cube Olds Jetfire Turbo F85 ever ran an Anti Detonation Injection system, and it wasn't free from miss-use, or in-service failure. The Edlebrock Varatronic water injection could take water or a 50/50 water alcohol mix, allowing a 4 point compression ratio rise without the need for anything accept pump 87 AKI, even on a 1970-1974 Pinto 2000 engine. The 2-bbl carb and one 16 thou jet down the primary was all that's needed for a 100 hp 9.2:1 engine going to 125 hp and 13:1 or more, even with a short duration 264 degree sohc Pinto cam.
If because of freezing in winter you aren't able to safely use either straight water injection, or the other 50/50 mixes of methonal/ethonol with a few percent of acetone to make the liquid free from delivery system degradation, you'll have to use 93 AKI. You can run 9.5:1 with 87, you just have to pull down your basic mechanical Duraspark plate to lower total advance while still being able to raise base timing to the 12 to 16 degrees static our engines really like. You may have to change the degree of retard in the stock timing gear if base cold cranking compression is too high. The mixture of cold cranking compression and Duraspark advance curve define how you'll cope if 93 AKI wasn't around.
The EPA/CARB and the relevant FMV standards are anti 16.2:1 lean cruise air fuel ratios, and anti high compression due to the NOx propagation when CR's above 9:1 are used on two valve engines which don't put a lot of paddle wheel swirl on the intake air fuel mix. Even an iron block variant of the modern LS alloy Chev V8 puts 300 paddle wheel revs at maximum lift, and that allows them to run huge compression ratios without emissions problems. Our sixes, except the Classic Inlines alloy head, are pretty stagnant for intake mixture spin, and this results in an Inability to go sky high on CR.
The other option is to use the Classic Inlines head bolt size, a standard Cross Flow Aussie head bolt, and there is a special 1986-1992 OHV 3.3/4.1 version which takes a knock sensor which allows a Thick Film Ignition system to be run off an EEC IV or Megaquirt ignition controller, allowing knock retard. The Ford TFI, Duraspark II and III systems had this on some versions.
