Hey, i have a bone stock lq9 in prestine condition looking to build to about 500hp through a 4l80 and 4.10 gears on pump and e85. I been theough all the 243/799 milling threads and theres mixed answers and half finished calculations (“etc” ) so i figured someone can help on my specific build
i have a hard time understanding what i am doing i just have a feel in the direction i am heading in.
10-1 compression lq9
.040 cometics gasket (for quench or something)
i got a set of 799 heads milled .20 and a set milled .35
stock cam, whats my compression ratio and quench?
how do i calculate PTV or static compression??
Id like to have a cam ground to my specs instead of working around the cam.
will be on a tbss intake with 50lb flex injectors.

 

stock cam, whats my compression ratio and quench?
quench is .040- crush. So, maybe .033 or so + piston out of the hole, which on LS motors is .007 to .010

I hate the myth that quench changes with milling. Only way to change quench (without changing pistons or decking block) is with head gasket thickness. You can swap all the heads you want on there, but quench is still determined by head gasket thickness

how do i calculate PTV or static compression??
PTV: you don't calculate. you check. But you are -.02 or -.035 right out of the hole

Math:
.006" removed = ~1cc. so -.02 is -3.33cc from stock. -.035 is -5.83cc

799s have 64cc chambers. 64- 3.33= 60.67, or 61. 64-5.83 =58.17 or 58

LS pistons are .007 to .010 out the hole (negative number on the calculator)

Head gaskets are ~.033 crushed

LQ9 pistons are flat

LQ9's are 4.00x 3.622



Handy calculator: https://www.summitracing.com/newsand...ion-calculator

799s on LQ9 with stock gaskets= 11:1 (iron LS2)
-.02 with .04 gaskets= 12:1
-.035 with .04 gaskets=12.7:1

 

So with that being said, how long will this engine last on e85 and 2” longtube headers? Not looking to put more than 200-300 miles weekly
im aware its also dependent on the tune.

 

forever if the tune is safe. Engine doesnt care so long as the octane, cooling and timing are all supportive of the compression ratio

 

What Arthur said^^^

 

12:1... that'll be responsive on the skinny pedal