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I have a open animal the pistion is .10 in the hole I bought a billet head to put on it my question is should I have the deck milled will it be beneficial in power gain?
It depends on what compression ratio you want.
Some of the billet heads have a pretty yield a pretty high compression ratio right out of the box which can result in blown head gaskets.
bore X bore X stroke X .7854 = displacement lets say 206 cc's
Add cylinder head volume (combustion chamber) Lets say 26 cc's
206 + 26 = 232 cc'c
232/26 = 8.92 to 1 compression ratio

When measuring the combustion chamber volume be sure to include the head gasket.
Probably the best way to measure the combustion chamber volume is to make a clear plastic (lexan) plate to bolt to the head gasket surface.
Put a 1/2" hole in the center of the plate.
Mount the head perfectly level and measure how many cc's of transmission fluid it takes to fill the combustion chamber with no air bubbles.
Another optional method would be using a cc burette measure the TDC volume and BDC volume. Then divide the BDC volume by TDC volume. This is the static compression ratio.
What would be a good compression ratio

Compression “is” the Holy Grail. Of course you have to match your fuel octane to the ratio you have. The higher the compression ratio, the more octane you need. In case you didn’t know; octane is a measure of a fuels ability to resist detonation. But there is a limit. Go too high on the compression ratio and you may need more octane than is available. What happens with fuel that doesn’t have enough octane for the compression ratio you’re running is detonation. Detonation is a real power killer, and it’s not all that easy to detect. I’ve found the easiest way to detect it is with an EGT gauge. Detonation causes a drop in the EGT readings.
Comments, compliments, criticisms and questions always welcome.
For sure detonation is bad, it will cause lots of engine damage. We use a Diamond detonation meter on our Superflow dyno for big engines and does a pretty good job at early detection based on vibration. I have not rigged up this kind of meter on our small engine dyno as of yet, but been thinking about it however lately. Most of the engines we build have a low enough CR ratio that this is not an issue with detonation.

The stock Animal stroke is 2.204"
When stroking the Animal most people put an additional .233" stroke in the motor.
That gives you a total stroke of 2.437"
It can be measured in various ways but probably the simplest is to use a digital or dial caliper.
Given the questions you've asked, I'd advise you to either have an engine builder assemble this for you, and maybe one who will list out what he did for you....would be my advise.
It sounds like you have the parts, to build or have built for you, a very potent engine.
Carb and cam are critical components to your engine and should be installed, and the carb modified, by an experienced, professional builder.
......Paul D.
actually its my nephew using my log in to ask questions.he wants to build engines.as for me i have been building engines for caterpillar for 20 years so yes im more than capable of building a engine.
I have a open animal the pistion is .10 in the hole I bought a billet head to put on it my question is should I have the deck milled will it be beneficial in power gain?

i'm curious how you have 0.010 piston in the cylinder with a stroker crank? when I built mine I had to mill about 0.090 off the top of my piston and it was 0.010 above the cylinder.
Can i ask how old you guys are? Al and Paul
Let me guess. Over 60
Act your age.
Since when did it become your privilege to discourage any one from asking questions on this forum.
Give the kid a break. He wants to learn something.
It make no difference how old he or she is.
I'm glad he's asking questions. If he bothers you then just don't come on here.
What are you going to ask next? What race or nationality are you?
Yes you can determine what the stroke is by measuring how far the piston travels from the top of the bore to the bottom.
its 0.10 in the hole because its a je pistion that comes pre cut down for the 233 stroker and i beleave they take 110 off of it it i remeber correctly