Thread: Best way to get a goo Dynamic Comp Ratio

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I the coming months I will be putting together a 327. I would like to get the DCR at 8-8.2. I know it can be done with the correct cam. But what about using a longer cam and advancing the cam to get the Intake closing or Milling the heads for a higher static ratio. Right now i"m just trying to learn something so I might just do this correctly for a change. And for the ones that will tell me to build a 350 or 383, I have most of what I need for the 327, It will replace a 307 so its already bigger,The other truck has my 383
Thanks Ed

Originally Posted by 53 Willys

I the coming months I will be putting together a 327. I would like to get the DCR at 8-8.2. I know it can be done with the correct cam. But what about using a longer cam and advancing the cam to get the Intake closing or Milling the heads for a higher static ratio. Right now i"m just trying to learn something so I might just do this correctly for a change. And for the ones that will tell me to build a 350 or 383, I have most of what I need for the 327, It will replace a 307 so its already bigger,The other truck has my 383
Thanks Ed

Ed, when you start putting your combination together before you have turned a wrench, you can do it any way you want to, long cam, short cam, high static c.r., low static c.r., whatever.

If this will be a street driver, then you will want to be able to operate on pump gas, so you will engineer the squish to be very tight, 0.035" to 0.040". You can do this with a zero deck and a 0.039" compressed gasket or you can have the piston crown down in the bore by 0.020" at TDC and use a 0.016" compressed gasket or you can pop the piston out of the bore by 0.015" and use a 0.051" compressed gasket or whatever. The deck/gasket combination isn't critical, just as long as you end up with 0.035" to 0.040" clearance between the piston and the head with the piston at TDC.

The next thing to consider is the operating range of the motor. If you're using OEM heads, then there is no sense in trying to buzz the motor to the moon to make horsepower. I would use a cam that makes power up through 5,000 or maybe a little higher. That way, you'd be making power down low enough that you wouldn't need a looser converter for instance and you could keep the static c.r. within reason. I don't know what you want out of the motor, I'm just throwing out ideas.

Here's the link to the DCR calculator. Just play with it. Plug in some different numbers and see what you get. I would try 9.0, 9.1, 9.2, 9.3, 9.4, 9.5, 9.6 and 9.7 static compression ratios and vary the closing point. When you work out your dream combination, make sure you can get heads and pistons to get to that static c.r. As far as the cam, any grinder can grind any figures you want on the blank, so when you do determine the actual closing point, that will be the closing point you will give the cam grinder to make your cam.
http://kb-silvolite.com/calc.php?action=comp2