I've been thinking my next mod is going to be a cam swap. I find myself looking at the xr259, xr265, xr269 but always coming back to the xr265, seems like the best all around cam, and it has gotten a lot of praise around here. After some talk about dcr i was wondering what kind of dcr that cam would give.

well after playing with this for a while..
http://www.wallaceracing.com/dynamic-cr.php

and plugging in specs using
http://www.compcams.com/Cam_Specs/Ca...csid=1085&sb=2
i came up with
Your dynamic compression ratio is 7.60:1 .
Your dynamic cranking pressure is 148.71 PSI.

which seems kinda low so i went to check out a similar grind from lunati

http://www.lunatipower.com/CamSpecCa...rtNumber=60510

the first thing i noticed is how much sooner the intake valve closes abdc

i went back to the dcr calc and punched in the new # and
Your dynamic compression ratio is 8.89:1 .
Your dynamic cranking pressure is 182.15 PSI.

seems much better to me, like less overlap, less reversion, and more power from a higher effective compression ratio. what do you engine guru's think?

 

I have a 60510 that I've been wanting to install in either my car or truck, but I don't know of anyone who runs it. It's their first step LS cam. 60511 and 60512 are a bit more lift. 60511 is probably a better cam, but you would lose bottom end I'm thinking.

http://www.lunatipower.com/CamSpecCa...rtNumber=60511

 

both of those cams are too big for my intended use, the 60512 is huge, it says right on there recommended for 6.6-7.0 not 5.3 dd cams imo

 

I think yoru calculations are off...
both cams are 212/218
The lunati is 113+4 ~7.72
The Comp is 114+2...~7.54

I believe you plugged in the wrong number cause the small differences in the two cams LSA and ICL does not equate to a difference of ~1.3 DCR.....

 

ok how did you do that, what numbers did you use?

 

I used numbers from a 4.8, but here is the spreadsheet i use to calculate DCR, CR and overlap.... The spreadsheet is set up for a LS1

 

hmmmm ok then does the lunati cam look better or should i stick with the xr265?

 

IIRC, you want about 7.5 to 8.5 DCR for a street engine on premium fuel...

 

Personally i would get 212/218 @ 110+4, but that is just me...

 

hey blackgmc i only have excel viewer, i cant modify the spreadsheet in any way, do you think you could plug in the numbers for the xr259 and xr269 for me too?
xr259
http://www.compcams.com/Cam_Specs/Ca...csid=1084&sb=2
xr269
http://www.compcams.com/Cam_Specs/Ca...csid=1086&sb=2