swapping pistons, max compression ratio

sciullo779

New Member
ok im dropping my crank and replacing my pistons because my oem ones rings are leaking and i want more power lol, so whats the highest compression ratio a 2000 ls, b18b1 can accept, 1 on stock internals and 2 on aftermarket rods and valves, and what kind of power increase would i see, or would i run too lean
 

Spody02

Name: Cody
your car is going to make more power if you mess with the head, i would just pull the pistons, replace the bearings and rings, get some head work done, or better yet throw a p72 head on
 

sciullo779

New Member
well i intend on getting my valves flush with the top of the cylinder, or doing a 3 angle valve job, and possibly porting/polishing the head, if i port it do i need new valve guides? and why shouldnt i bump the compression up?
 

Spody02

Name: Cody
no, not saying that at all, bumping the compression is great if you want to make all motor power, but i have heard too many storys when someone opens up the motor and throws some need rods and 12 to 1 pistons in and doesnt make that much power, most of your power comes from your head

do some messing around with this

http://www.c-speedracing.com/howto/compcalc/compcalc.php
 


tilegend

New Member
compression ratio is dependent on a lot of things. not just the pistons itself. and aftermarket rods aren't going to affect compression b/c most likely you're going to get stock sized rods. and flat faced valves will bump up compression a little bit.

also do you have the necessary octane requirement to run higher a c/r?

all this seems unnecessary unless you have some cams going in there too.

not only that but you're going to need a tune also for the higher compression.
 

sciullo779

New Member
i intend on getting crower cams, pistons, porting my head myself, gasket matching, and new crower valves,

and i can get up to 93 here, and i wanna build my motor in increments not all at once so idk about the tune

and will 11:1 maybe 12 or 13:1 pistons have enough valve clearance on a b18b1, also are gsr pistons and rods/type r rods compatible with the b18's crank?
 
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tilegend

New Member
so i guess you're doing an LS build.
crower cams.... which one? 403s? 404s?

gsr and type-r pistons need to be modified to fit LS rods... the rods need to be milled to fit.

if you use the USDM P73-A0 ITR pistons you'll end up with 11:1 c/r

the JDM P72-00 GSR pistons will end up with 10.7:1 c/r

USDM PR3 B16 pistons end up with 11.4:1

(no milling, stock head gasket, no block decking etc) also give or take a tenth...

those are basically all safe numbers to stay with when using 93 octane.

you can play with all the numbers by using a compression calc. or by doing the math yourself.

http://zealautowerks.com/bseries.html

valve to vale clearance depends on the cams you have...

also goes the same for piston to valve clearance.

to find out the definite answer would be to clay your motor w/ the cams... or if you know how you can use dial indicators to actually measure it.

this is also a good way to find out your clearance if you decide to use cam gears.

also if you don't want to immediately tune but want a map slightly better than stock.

www.xenocron.com / http://phearable.net/ are a few that offer basemaps and chipping services.

also this is a good read on LS non-vtec builds
http://honda-tech.com/showthread.php?t=2108181
 


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TegSox

Super Duper Moderator
sciullo779 said:
and i can get up to 93 here, and i wanna build my motor in increments not all at once so idk about the tune
Click to expand...
If your going to raise your compression as high as your talking, you have no choice but to tune. You'll need larger injectors as well.
The max compression you can run on pump gas is around 12.5:1, but it depends on the tuning.
 

sciullo779

New Member
i was thinking 403's so i cam bump the compression up to 12:1+ without valve clearance issues, how does compression affect hp and torque levels and curves?
.....

well i wanted to do an engine build, but now im thinking about turbo, so my compression test gave me 185, 185, 185, 190, so i think thats good enough, i was thinking about doing head work, like a diy port/polish kit, maybe new valves? any input?
 
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