LLY: Compression Ratio

A_T_Ver

Member
Jul 31, 2007
416
0
16
Going to start an LLY build. Wondering what CR to go with. Truck will be mainly street driven, with some drag racing and maybe a few pulls. Going to use Fingers oval bowl design. I know stock LLY (05) CP is 17.5:1. So would dropping a point or point and a half be good? Less or more? Pros and cons? Thanks!
 

TROJAN366

Gold Rush
Jan 13, 2012
2,474
1
38
MASS
Just from seeing threads like this in the past I would say higher is better where it will be a daily driver. 16.5-17 would probably work well
 

S Phinney

Active member
Aug 15, 2008
4,008
18
28
Quncy, Fl
Dont go I to the 15's unless its a dedicated competition truck. I have done it there and the 17/1 that I use now is definitely without a doubt better.

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MarkBroviak

DMax Junkie
Vendor/Sponsor
May 25, 2008
2,134
463
83
Danville Indiana
15.25:1 in mine and love it! It all depends on your build and the power you plan to make with it. If you aren't going north of 650-700hp then stay close to 16.5:1 and you'll be fine. If you plan to go pass this by much then you need to drop the compression. Did a workstock built motor with Finger's pistons in race cast at 15.5:1, 100%injectors dual fueled and DP BMW2.5 VGT turbo and made 728hp 1489ftlbs and he is averaging over 18mpg with on 35's. The compression ratio is just a small piece of the puzzle.