HUG WEDGE WORLD TECH A13 TECH INFO ABOUT COMPRESSION RATIOS $0.00
 WEDGE WORLD TECH
From Hughes Engines
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World of Mopar wedge engines
Issue #13 Compression Ratios
I apologize for not making this issue an earlier subject. I did not realize there was so much mis-information or mis-understanding about compression / compression ratio / cylinder pressure. The compression ratio is just one factor in deciding what you need when building an engine.
It is not important what compression pressure you run it is very important! And it seems as though most of the time stock engine guys ignore this factor. Probably because it cost more money or no one told them.
Know this: All of the factory specs on compression ratios are based on max effort blueprint numbers. And that is not what you get off the assembly line. They are looking at long life for the average owner and power items like compression ratios are on the “safe” (read low) side.
For example, the actual compression ratio on the 5.2 and 5.9 magnums is about 8:1 (Whoa is that misprint) no, it is not. I know they are advertised @9:1’ And that means that putting in a cam can actually reduce the power output of your engine or make it so that you need to rev the engine a lot more than normal to feel any gain.
So why would putting a higher performance cam in hurt the power? Because of the performance cam’s specs (valve opening and closing points) lower the cylinder compression pressure. Remember the compression pressure does not start until the intake valve closes.
But cylinder pressure is actually what you need to build. The closing point of the intake valve will be later on a performance cam, than on a stock cam delaying when compression buildup starts.
Yes, the higher compression ratio pistons or heads or stroker kit can help raise compression ratio or bring it back to where it needs to be.
We hear from lots of guys who want to build up a low compression engine but don’t want to buy a stroker kit, or pistons to make the compression they need. Or have purchased a cam that don’t give them the power they thought it would.
Well, I don’t have good news. You need to remember what the famous NASCAR racer and engine builder Smokey Yunick said, “Building horsepower is like when a monkey wets on a cash register it gets into the money” If you aren’t ready to do it right (buy the parts you need) you probably won’t be happy. Why? Cylinder pressure is what pushes the piston down which in turn turns the crank and tires. | 
