2056 Build Options

[SteveNMaine]

I am trying to work out compression ratio of my 2056 build. In calculating head volume my understanding from the forum is that stock 2.0 heads have 57mm and the valve pockets on the pistons I am going to use is 3mm. Do I add these together to use 60mm in my calculations for head volume?

[technicalninja]

I am trying to work out compression ratio of my 2056 build. In calculating head volume my understanding from the forum is that stock 2.0 heads have 57mm and the valve pockets on the pistons I am going to use is 3mm. Do I add these together to use 60mm in my calculations for head volume?

Yes, you add the combustion chamber volume to the volume of the valve pockets on the top of the pistons. You figure out these two volumes by doing what the above posters said. You actually measure the volume.

Suggest you use one of those plastic circles with a hole drilled in it. Along with a burette with rubbing alcohol with a drop of food coloring in it. Best wishes for getting your compression ratio right.

I used my kids crayon clay and compared it to oil, came out the same for me but mileage may vary. You just drop the clay in a graduated cylinder with water and watch the displacement. It's clean and easy but I have access to stuff like graduated cylinders.

The use of clay and a burette is a good idea.
Not sure about the alcohol, might work fine, evaporates so fast that it MIGHT cause inaccuracies. Normally I just use antifreeze.

I use a bunch of alcohol in my Automotive AC business, probably 100 gallons a year.
One thing to ALWAYS be aware of is the fact that alcohol burns with a flame that you CANNOT see unless the room is dark.
You can be ON FIRE and not know it!


The actual clearance volume measurement is a bit more complicated.
+Head CC
+ valve pocket CC
+ deck height CC
+ clearance around top of piston to first ring land (usually around 1cc)

In the case of a stock 2056 flat top at optimal quench (.040") with two 1.5cc valve depressions would go like this.

Head= 60 measured
Valve pockets 3 measured
deck height at .040 7 calculated
upper ring clearance 1 calculated

total "clearance volume" of 71cc

Swept volume of 514 (calculated)

(Swept + clearance) / clearance = compression ratio
or
Swept / clearance +1 = compression ratio

514+71 / 71 = 8.24

No valve reliefs and 55 cc heads
clearance = 63
63+514 / 63= 9.16

One of the reasons I decided to not walk the T4 route is the difficulty in hitting 10/1 ratios without stroker cranks/ pistons larger than 96mm or other "fully bespoke engine" type mods.

That second example, which is just over 9/1 will require verifying valve to piston clearances and it will most likely limit valve travel.

And it gets more critical as valve diameters go up.

And all this measuring and calculation means NOTHING AT ALL if you haven't properly selected the cam you will be using.

The engine actually runs on what is called "dynamic" compression ratio.
You cannot verify this by measuring. It takes a dynamic compression ratio calculator program. Dynamic compression ratio is often 2 full points LOWER that static comp ratio (10/1 engine is really an 8/1 engine!).
Higher static compression ratio DEMANDS larger duration camshafts...

Compression ratio, available fuel octane, intended use, expected RPM range, transmission gearing, induction and exhaust all factor into your camshaft choice.

Raby is RIGHT!

It's the total combination of everything that makes it work!
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