10 20 30 over

[Anonymous]

ok after boaring out and engine how do you determine what size it is. like how many inches does 10 over give you and so on. or is it different on evry engine. depending on what size you start with.



hopfully I am making sense.


thanks
66stang

 

[Anonymous]

Well,

If it's a 200 a .010 overbore should equal a 201ci, .020 a 202ci, .030 a 203ci, etc, etc.

Usually the online compression calculators will tell you also.

Later,

Doug

 

[Hot 6t Falcon]

Doug gave you the right info about the increased sizes.

If you want to play yourself, click on the link in my signature. Then click on "Compression Calculator" in the left side bar.

We have the data set up for a "stock" 200. Click on "Calculate." You'll get the data at the bottom of the screen.

Now add .010 to 3.68 (3.69) and click "re-calculate". Notice how the info changes at the bottom of the screen.

Good Luck

 

[Anonymous]

Dennis or David.

On that compression calc, how accurate is the deck height? That is are those more or less the factory set specs?

I know things vary greatly but are those numbers for a new 200 thats never been decked in a rebuild?

 

[63comet]

HEH EVERYONE, YOU WILL HAVE TO MEASURE EVERYTHING YOU DO BECAUSE, "USUALLY" WHEN YOU GET OVERSIZED PISTONS, THE PIN HEIGHT IS SHORTER TO ALLOW FOR CLEANING UP THE BLOCK. FOR EXAMPLE, WHEN I BORED MY BLOCK LAST WINTER, I THOUGHT AFTER MEASURING, I COULD BORE OUT .030" OVER AND CLEAN UP THE CYLINDERS, WHEN THE PISTONS CAME, THEY WERE .020" SHORTER PIN HEIGHT, BUT WHEN WE BORED IT .030" OVER, THE #1 CYLINDER NEEDED AN EXTRA .010" TO CLEAN UP SO I HAD TO GET .040" OVERSIZE PISTONS, WHEN I GOT THESE FROM THE SAME COMPANY, CLEVITE. THEY WERE ONLY .010" SHORTER PIN HEIGHT, SO NEEDLESS TO SAY, I HAD ALREADY DECKED MY BLOCK FOR 0 DECK HEIGHT AND NOW MY PISTONS POKE OUT OF THE CYLINDER .010". NO PROBLEM WITH THE NEW HEAD GASKETS. SO MEASURE EVERYTHING. I'M OUTTA HERE.

 

[MLINE]

Just in case you want to know how to calculate engine displacement on your own, find the displacement of a cylinder and multiply by six.

(Radius of bore squared) x 3.1416 x Stroke x 6 = displacement

Radius = (3.680 + .010)/2 = 1.845

(1.845 squared) x 3.1416 x 3.126 x 6 = 200.578 cubic inches

I apologise if it's not to clear.


BTW does anyone know how to superscript and type Pi symbols?

 

[CZLN6]

Howdy KCStanger:

The setting are an average, based on a compulation of published factory specs, and actual measurement from many heads, gaskets and blocks. The three with the most variabliity are chamber volume, compressed gasket thickness, and deck height. I tend to reset these three in estimating on an unknown '66 200 to; Chamber volume=52cc, compressed OEM shim gasket thckness=.025", and deck height on an original block=.025".

63Comet makes the best point of all- unless you take it apart and measure carefully, you're only guessing.

late model 200 heads Chamber volume, best guess=62cc

Aftermarket Composite gasket compressed thickness=.045" to .055" depending on the manufacturer.

When figuring compression ratio, it's best to error on the conservative side. And know that the crevice between the piston and the cylinder wall, above the compression ring, is not figured into the CR formula any where. That also give a very slight safety margin. It is very difficult to measure and will likely be considerably less than 1cc.

Adios, David

 

[Anonymous]

hey thanks guys. yea I wanted to know how to calculate it my self.


thanks
66stang