Just wondering what the disadvantages to raising the compression ratio in the motor would be? I know that it raises the HP, but is where is the point that enough is to much? I'm thinking that maybe I broke a ring in my motor, and figure that if I'm gonna take the motor down far enough to fix that, I might as well get the '70 Stage 1 pistons and bring the car back to the way it used to be, if not a bit more. I see a lot of cams require a certain compression ratio to run correctly and saw pistons that go from 8:1 all the way to 12:1. I just wonder if going from a set of 10:1 pistons to a set of notched 12:1 would make that much of a difference in the performance, and what the drawbacks to that are?
Could you define what you use the car for. This will help in getting you to the best possible compresion ratio for your car as you use it. For example, I run 13:1 in my car. I use 113 octane race gas, 150$ head gaskets, never drive on the street and trailer my car to and from the race track. But since I only race my car, I don't see these things as disadvantages.
You can safely raise your compression to about 10.25 as long as you've cleaned up your combustion chambers and piston tops and still run 93 octane with no problems. Higher compression means more complete combustion, hence more horsepower.
I'm just looking to drive on the street, or maybe at the track occasionally. It's by no means going to be a daily driver, but would want it to be able to be highway driven if need be, to some events. I don't mind using 93 octane gas, but the racing fuel @ $4 a gallon is a bit more out of my league. :laugh: I'm guessing I'd put about 1000 miles a summer, at the most, on it. Most of this would be from the local cruises and shows around town. The original motor was a Stage 1, and I'm looking at putting the new '71 motor, up to the same peformance level. I'm not looking at putting the 12:1 piston it (They're wayyyyy out of my budget for now), just wondering if they make the motor work harder or are harder on the motor, as far as wear and tear.
In that case I would follow Phil's recomendation and polish the chambers and piston tops, then set it up for 10:1 to 10.25:1. No real down sides to this other than useing 93 octane. You'll pick up some power over the 8.5:1 set up, maybe a little heat also but not enough to worry about. Higher compression is harder on the engine (10.25:1 is not high). I don't see people having problems until they're up around 14:1. Most racers anymore don't even see my engine as having high compression at 13:1. A vast majority of class racers and Quick racers are now at 16:1 plus, but these are high maintence moters where they replace the bearing quite frequently. Hope this helps. Maybe others could chime in with their opinions. There is more than one way to skin a cat.
Personally, I've always run street 455s with low compression (71-74) pistons and early heads, for just below 9:1 compression. I can drive all day (like to Bowling Green :beer ) on the cheapest gas available, and use 93 at the race track. I'm willing to give up a few horsepower for convenience/peace of mind (I've killed 10:1 motors with cheap gas and ignoring detonation, in my poor college student days )
