Comp cams xe268h for 318

dartfreak75 said
Working on it I will try to get it done in the next day or two. How do you get the dcr number ? What info do you use?
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Here is the calculator I use; go to the bottom of this page and install the tool on you computer:
Dynamic CR

Select "DCR Calculator with VB6 Runtime Files". It is for most up-to-date Windows operating systems. It's free. (VB6 is Visual Basic version 6, which is a Microsoft program.)

This is a nice tool because it does SCR and DCR and figures out intake closure angles for you all in one place. Let me know if you want to use this, and I'll see if I can figure out how to post some pix of filled-in data and the resulting output so you can see what to put in.

BASIC USE OF THIS PROGRAM
The program has 3 tabs, and is used in 4 steps.
  1. Enter engine/head data on tab 3 and hit "Calculate" to get SCR in the bottom box. (If you want just SCR, then use this tab only.)
  2. Enter 4 pieces of cam data in the top half of tab 2 and hit "Calculate". Note that the duration you use is the cam's "advertised duration", NOT the .050" lift duration. (There are some mods to the data entries with some cams (like mechanical cams) but that is not needed for hydraulic cams.)
  3. Then go to tab 1, enter stroke and rod length and hit "Calculate"
  4. Finally, go back to tab 3 and check the box on the 'stroke' line and hit "Calculate" again and the DCR will appear in the bottom box
There is one clunky aspect of this tool: If you change any cam data on tab 2, then you have to:
It takes a bit of work to dig out the data to know what to put in, but once you know it, you can run a combination in a minute.

A NEXT STEP IN DCR DATA (if you want more info)
This tool does not tell you 'effective DCR' with elevation, or cranking pressure. For that, I go to the results on tab 2 and pull out the 'intake close ABDC' number (the ICA, or intake closing angle), and the SCR data on tab 3. Then put that info into the Wallace Racing Dynamic Compression Ratio Calculator (you can google search for that), and put in the other data, including your elevation above sea level, wiht 0 boost for a carbed engine. That simpler tool will put out the 'effective DCR' (which will be lower above sea level) at your elevation, AND expected cranking pressure.

Why bother with 'effective DCR'? It shows what will happen to the cylinder filling process at elevation; the air pressure is just plain lower and so for a carbed engine, it will simply get less fuel-air mixture pushed in each cycle, and will have less torque/HP. The less the 'effective DCR', then the less cylinder pressure and torque you will have.