You'll obviously need Excel. I've posted these before, but I've made some improvements and clarifications since then. If anyone sees anything that should be addressed, please let me know.

Start with this sheet if you have an LS1

Start with this sheet if you have an LS6

Start with this sheet if you have an LS2

Step 1:
Open the spreadsheet and plug in your Comp cam's Duration (@ .050) and Lift.


This allows the spreadsheet to look up your durations at .006 to calculate your DCR. NOTE: For all Comp grinds per the catalog, the duration is an EVEN number. If the vendor quotes anything different, they are just trying to be mystical or perhaps using the specs from the Cam Doctor (if you have a cam card, you can plug in all your specs on the "DCR Manual Calculator" tab). For the Lookup function, you must use an even number. Additionally, the LIFT you use MUST correspond to the lift in the catalog in order to find the .006 duration. See the below image for a portion of the catalog (which can also be found on the "Lobe Source" tab in the spreadsheet). Usually, you can get the "correct" lift by experimenting and moving the lift value up or down by one thousandth, or you can just click the tab to look it up if you don't want to guess. To use the "Lobe Source" tab, simply find your grind type (probably XE-R) then go down the column that has the .050 durations until you find your number. Then, look one cell to the right and that is the number you need to enter for that lobe.



Step 2:
If you are only doing a cam swap (and you chose the proper spreadsheet to start with), you're done! Click on the orange "DCR" tab and look down at the orange number in the row "Dynamic Compression Ratio." If you're going to be milling the heads, change that number as needed. If you're going to use a thinner gasket, change that number as needed. If you know your exact deck height, change that number as needed. I think you see a pattern here...



FAQs

Q: Why does #N/A appear on my "DCR" tab?
A: You've probably entered a "wrong" lift value per Comp's catalog. Go back to Step 1 and re-read the instructions.

Q: Why does this only work for Comp cams?
A: I could not find similar specs from other manufacturers. If you would like to provide for me similar specs, I would be happy to add them.

 

I nominate you for LS1Tech Excel Guru!

Awesome idea, but I bet there will still be plenty of peeps who can't figure out DCR on their own.

 

im going to try very hard though!!!

 

Pretty nice. Its worth it to just have the lobes all in one place.

I notice that you compute a 10.37:1 static compression. I thought that stock was 10.2 or just a hair under. This is on the "DCR" tab. On the manual DCR tab, it is 10.06 CR. It appears that the difference is two different values for deck hieght.

Update: Published specs for an LS1 were 10:1

 

I agree. DCR calculators have been out forever, but people just can't seem to figure them out.


Nice work on the spread sheet though!

 

LS6 and LS2 manual tabs need updates too.

 

I used your file to design my cam, thanks man!

 

Done.

 

Yes, I'm not sure of this discrepancy but I compared the values on this calculator with others on the web and the proper deck height is the negative value. Even assuming a deck height of "0" that still gives 10.23:1 SCR. Is it possible GM uses a different figure for compressed head gasket thickness or chamber volume?

 

Are you sure that it isn't positive .006 rather than negative? Positive .006 puts it right at 10.1

I'm pretty sure that 10.37 CR is too high for a stock LS1, so I'm changing it in my copy of your sheet.

 

11.88 SCR and 8.91 DCR

 

Yep, positive. Like I said, I compared all my values using other calculators online and it's definitely supposed to be a negative number. Plus, doing it your way, you may THINK you're at 8.7:1 and right on the "edge" but really you're over 9:1!

Just to clarify, this is J-rod's calculator. All I did was make it pretty and more user-friendly.

 

Going up for input

 

Very nice. My productivity at work has dropped, but at least I know my VE's and how much to get my heads milled and what thickness gaskets to run. I'd just like to get a concrete answer on whether deck height should be a + or - value. I'd think - but I'm no expert.

 

It's a negative number.

 

Maybe you should add, "+ for below the deck, - for above the deck," or something like that because that fumbled me too. I had to mess with the + and - to figure out which one meant out of the hole, or in the hole.

 

Maybe someone needs to tell us why a stock LS1 is really about 10.4:1 not 10.1:1 and an LS6 is really over 10.7 then.

 

I'm up for an explanation.

 

I'll do that later tonight.

 

Maybe i'm an idiot, but I cannot get this to work. I have a tsp 233/239 .595/.603 cam. I think comp grinds the cams for tsp. Which even values should I use? How do I find my grind?