3.504

Hi everyone, i have alot of information to post. I'm going to try to keep it as simple as possible.

I cc'd my LS (b18a1) head today and ended up with some wacky numbers.

my build is this:

B18a1 block, deck milled .010", 3.504" crank, 5.394" eagle rods, JE 3.2053" pistons, 3.2104" bore

b18a1 head, milled .010", crower 0.5mm over valves


the pistons are supposedly 11.7:1 c/r, but this ratio is for an ls block with a pr3 head. i'm running what i thought was smaller chambers with head and deck mill. i cc'd the piston dome and came up with a number of +0.7cc's. the piston itself looks slightly more aggresive (taller dome) than a JDM ITR, but i only got 0.7cc's of dome, i guess cause the pockets are so deep.

i've always heard the LS head has 38cc chambers, and if this was true, my static compression would be over 13:1.

i cc'd my cylinder 1 chamber and got 44.6cc's. if you add the gasket (3.5cc's) and subtract the dome (0.7cc's) you end up with 47.4cc's.

the formula goes: (cylinder volume + chamber volume) divided by chamber volume gives you compression ratio

when i plugged my numbers in (3.2104 bore, 3.504 stroke, 47.4chamber cc's) i came up with a static compression of 10.80:1.


i dont know why, but this compression seems so low for what i thought i had. the pistons are supposedly 11.7:1 and i'm using supposedly smaller chambers than pr3's or p72's have. i can't argue with the numbers i measured... what i'm trying to say is maybe what i've heard (about chamber size) is completly wrong and maybe every b-series head should be cc'd to find the correct numbers.

so my question is: what are the LS chambers supposed to be? my numbers are 44.6cc's and i did it twice using alcohol with a cc burette and a flat plexiglass cc-plate.

3.504

i was just informed that LS's have a stock spec of 45cc chambers....

also heard 41.6cc's for p72's and 42.7cc's for pr3's

so if 45cc's is stock, with my .010" mill, i'm right on par with my measure.

can anyone confirm a stock chamber volume of 45cc's