ahhh! I have spent the last two hours trying to figure out my dynamic compression ratio for the 91 octane 383 I am trying to build as a sort of street, lots of strip motor I was going to put in my car for a while but its driving me up the wall! Right now I am using Patrick Kelley's DCR calculator (as recommended by many here on this board) and I am coming up with a SCR of 11.409 and a DCR of 10.8. These numbers make no sense to me, that DCR is pretty darn high and I know some guys on this board run that cam in their 383. I thought maybe this calculator was flawed so I used the calculator on KB's web site. I got a SCR of 13.006 and an DCR of 10.797. ahhh!
The plan was to use a gm847 with a 3.75 stroke crank with 6" rods. The piston reliefs I was using was -5cc because I am hoping to use the mahle powerpak on this motor (good product for the money). Could anybody gander a guess at what I am doing wrong?
I am using 4.03 as bore size and gasket bore, .027 as the deck, .051 as my gasket (I use the stock GM gaskets, they always work ok for me), my head size as 54 cc(that, unfortunately is a guess, my heads have been shaved down a bit so I figure that number is about right), 296 as intake duration, 75 as intake closing angle in use, 107 as intake centerline, 112 as lsa..... I think that just about covers it. any one able to figure out where I went wrong? or do I need a new cam or a piston with bigger releifs?

 

http://www.cranecams.com/?show=brows...tType=camshaft

Use the .004" #'s. Keep in mind comp uses .006" for advertised duration so it will vary from trying to compare between companies. And there is alot more than DCR to figure if you can run on pump gas, but I guess it's better than nothing.

 

I just plugged in your #'s and got 11.33:1 compression and 8.33 dynamic.

 

which calculator did you use?

 

Downloaded it off ls1tech.

 

which one off of ls1tech, I have just used three different ones and so far the most unique number had a dcr of 15.7