Alright...I'm slightly new to the sight but i need some serious help. I'm doing a rebuild of an LS block and i'm keeping it all motor. I already bought a rebuilt head thats been machined but i need to know what would be the best compression ratio to use. I don't want to go to far to the point that i'm getting serious knock but i don't want to go so low that i don't get the power i want. I was planning on using some forged, 11.5:1 pistons but my dad(who has been helping and supporting me through this project) thinks that would be to much. Does anyone know what piston compression ratio would be safe yet still bring out some serious power in an all motor LS??

 

I wouldn't go to high on your compression ratio if your gonna be running pump gas

 

Alot of guys that build the LS motor will use PR3's or P30's, they yeild 10.8:1 and 11:1 compression ratios respectively and fit stock LS rods without modification. If you go with stock rods, use ARP rod bolts and have the big end resized.

There have been several B18A/B builds using 404 cams and PR3/P30 pistons that attain 165-175 whp and nice torque. Mate that with a short geared B16 tranny and have yourself some fun.

 

It also depends on what cams you're going to run. That will change your dynamic compression (how long after TDC the valve stays open). The "11.5:1" is static compression. I see no problems with 11.5 on 93 octane gas, however much like sam92teg said, the US/JDM B16 pistons will bump your compression up (the CTRs will yield 11.4ish but I believe you have to machine those/your rods for them to work). Forged pistons are great and everything, but in all honesty, they are overkill for your setup. Stock pistons can hold 250whp with little problems.....I say get the OEM pistons and spend the extra money on getting it dyno tuned.


Also, incase you havent found your way to the compression calculator....heres a link to one. There are others, but this one is probably the easiest/simpliest....minus the one that had the pretty little drag and drop pictures, but I think it got taken down.
http://www.c-speedracing.com/h...c.php

 

hit up ebay. they have OEM Honda CTR or ITR pistons for under $200. You dont need anything higher, I wouldn't take the risk of detonation..

 

ctr pistons are VERY different from itr pistons...

just get your self some pr3 pistons. they are relatively easy to get your hands on.

itr pistons doesn't even have as much compression as the pr3 does. ctr pistons are just way damn over kill..... unless you want to run race gas everyday.

 

11.4:1 is way overkill??? To think a stock RSX has 11:1.....

 

95 integra.. kinda off subject nut our turbos look alike what kind u got?

11.4 is not overkill. i ran 11.7:1 on my ls/vtec. ran like a monster on pump gas with out a problem.

 

GT4088

 

thanks for the feedback guys.....to help everyone out a little bit more heres my whole set up i'm working towards....

Stage 1 Crower cams
Cam gears
valve springs and retainers
(i already have a rebuilt ls head that has a three angle valve job and so on)
lightened crank
machined, honed block
heavy duty clutch
streetlite flywheel
...and then of course theres all of the bolt on bull

What i'm trying to do is run the highest compression i can with that set up and not have to worry about fuel and knock....i'm not necessarily a noob at this stuff but never really looked into all motor rebuilds....all your help is what i need lol so any advice you guys have just throw it out there....thanks!!

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Aro321 &raquo;</TD></TR><TR><TD CLASS="quote">
What i'm trying to do is run the highest compression i can with that set up and not have to worry about fuel and knock....i'm not necessarily a noob at this stuff but never really looked into all motor rebuilds....all your help is what i need lol so any advice you guys have just throw it out there....thanks!! </TD></TR></TABLE>

Fuel is key, not the octane, but the quantity thereof. Its all about tuning, make sure you get a GOOD tune (not a decent tune, a good tune). It might cost $700 w/ engine management and dyno time/tuning, but its the only thing that really matters in the end.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 95 integra &raquo;</TD></TR><TR><TD CLASS="quote">GT4088 </TD></TR></TABLE>
that sucker is a tad bit bigger than mine. yours is rated 450 - 700, mines 350-600. Sick

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by akandok &raquo;</TD></TR><TR><TD CLASS="quote">
that sucker is a tad bit bigger than mine. yours is rated 450 - 700, mines 350-600. Sick </TD></TR></TABLE>

Bigger motor, bigger car.....I "need" the bigger turbo. Should be pushing right at 550whp (which is where the turbo will give out). Ofcourse in my current jobless situation, its going to be a year before it actually goes on.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 95 integra &raquo;</TD></TR><TR><TD CLASS="quote">

Bigger motor, bigger car.....I "need" the bigger turbo. Should be pushing right at 550whp (which is where the turbo will give out). Ofcourse in my current jobless situation, its going to be a year before it actually goes on.</TD></TR></TABLE>
haha.. youre jobless... but im getting married... but same **** we still broke in the end.. race you in a year

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by akandok &raquo;</TD></TR><TR><TD CLASS="quote">
haha.. youre jobless... but im getting married... but same **** we still broke in the end.. race you in a year </TD></TR></TABLE>

bwhahaha......the difference is, in a few months I'll have a job and you'll still be married .

 

I have some B18A/B rebuild parts for sale, if you decide that 10.8:1 compression is right for you, have a look. Also have ACL bearings and Hasting rings to go with.
http://www.hondamarketplace.com/zerothread/1844030

 

are hasting rings any good? i usually use JE. they run about 90-110. I think that the price difference is well worth it..

 

Hastings rings come with many aftermarket forged pistons as well as an OEM supplier. Type Hastings into the search engine here or google and see for yourself.

 

you were right... i had no idea. i try to stick strictly to OEM or well known aftermarket suppliers, but hastings is an OEM supplier... Learn something new everyday. Do they make them oversized?

 

"Hastings Manufacturing designs and manufactures piston rings for OEM's worldwide, including DaimlerChrysler, Ford Motor Company, General Motors, Harley-Davidson" When Dodge, GM and Ford are your top customers, that means you must make some cheap, shitty products, which is the precise reason I wouldn't run them. I mean, GM has release a TSB saying that it screwed up on the 3.8L engine (ie, crap thats in every car they make) and that its "normal" for them to burn a quart of oil every 1,000 miles on a car that has 30k on the ODO.

 

hey, do you have a supra?