I have an OHV Ford V8 with 8.0 factory compression. I am thinking of raising it to 9.5 or higher. I want maximum compression for power and sound with todays 93 octane fuel. What are the benefits of going from 8.0:1 to say 9.5:1? What would be a reason not to raise the compression. How high can I go with iron heads? How high can I go with Edelbrock aluminum heads?
I'm running 9.7:1 with Trick Flow alum. heads. I expect you can go a bit higher, but then when you get some carbon buildup from cruising around town, you'll have a problem. And gas sure as Hell ain't gonna get any better, I'll bet on that!
the max you can go is 10/1. You need rpm and heat not much idle time. A shot of octane booster in every second tank of fuel will help.
Its your DCR that will dictate the boundaries of what your max compression can safely be. There are many online calculators to find out what yours will be.
I'm running 10.4 :1 static with 7.9 dynamic. Tight quench is important as well as the tune. A high compression engine is way way wAy more efficient than a low compression engine. You'll have more power and better economy with high compression. Your NOx levels will be higher than EPA standards.
I would like to get 10:1 or even 10.5:1 ratio. If I replace the dished pistons with flat tops, I will have about 9.6:1 with 58cc heads. I found some true flat tops pistons with no valve reliefs. These may get me to 9.7:1. Any way to get even more compression without a pop up piston? Very thin head gaskets? Milled heads?
Without doing a dynamic compression ratio check, then 9.5:1 static compression ratio is the safe limit and that's running 91-93 octane fuel. The benefits of more compression are increased lowend torque and better fuel mileage. The timing curve will need to be altered to take full advantage of any compression ratio increases.
I guess I will have to google dynamic compression because I don't really know what that is. In my hemi, I have 10.7:1 ratio. With a mild cam I have 230psi cranking compression. I have no issues with 93 octane gas and aluminum heads. I had this motor professionally tuned on a chassis dyno. Maybe the tune allows me to run this high compression on 93 octane? Thanks guys, I appreciate all of your advise.
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