markp03

iTrader: (4)

first off i need a little help figuring out compression, I want to run low compression with my stock ls1 heads, i talked to a guy who says he has mahle pistons with a -16cc dish and says he has 8.7-1 CR would i need to do more then just get -16c dished pistons?

i was checkin out e-bay and found this

http://cgi.ebay.com/ebaymotors/ws/eB..._BIN_Stores_IT


think thats a good setup? i am looking to run about 850 wheel HP (FI) would i need to upgrade to the billet rods for the extra 110? also i talked to the guy and i can get -16 dished pistons for lower compression.

jrp

iTrader: (16)

those are gen 1 and II pistons and rods, unless you specifically spoke of a genIII piston/rod combo with the dude.

and your CR will be dependent upon a few variables.

markp03

iTrader: (4)

ahhh ok....sooo (dumb question number 2) whats the difference?

kpowr82

iTrader: (9)

GenIII = LSX engines. GenI and GenII = GMs other SBCs

Your best bet would be search ebay for "LS1 piston/rod combo"

Beast96Z

iTrader: (21)

LS-1 based rods and pistons are specifically for LS-1's. The ones in the auction are for old school SBC's. For what you are wanting to do, I would reccomend looking into some SCAT H-beams or the Compstar rods. Both will handle what your wanting to do. Mahle does make LS-1 pistons, along with Diamond and many others. Plan to spend at least a grand or a little more on a good rod/piston combo for an LS-1.

markp03

iTrader: (4)

do you guys know of any other "fairly inexpensive" piston rod combos around?


*edit thanks beast...can anyone tell me what piston specs i need to do to get around 8.5-1 CR with stock ls1heads

Beast96Z

iTrader: (21)

The Eagle rods will be the least expensive and still be forged. They will run you about $450. The SCATs are a better rod and will run you about the same. I got a good deal on my SCATs in a package deal for $420. The diamond and Mahle pistons seem to be more "budget" friendly when it comes to pistons.

jrp

iTrader: (16)

im running a diamond/eagle combo myself, the newer compstars are a really fine piece that i'd of got if they were out at the time.

i assume your staying with your ls1 block and the stock bore with a hone. in that case go with a 3.905 bore piston, 6.125" rods are what most guys run. with the longer rod your piston CH will be in the 1.315 range. you'll need to know your deck height and gasket compressed thickness as well to figure out your CR.

you'll need a approximately a 20cc dish to reach 8.5 using -.008 deck heigt and a .045 cometic with a 67cc head volume.

Beast96Z

iTrader: (21)

I figured a 19cc dish using a stock gasket so now you have 2 diffrent gasket types covered.

markp03

iTrader: (4)

so will bolting up a scat rod and a mahle -16dished piston to a motor with stock ls1 heads put me at around 9?


also i found a site
http://www.rbracing-rsr.com/compstaticcalc.html

what are our motors deck hight?

if i put 0 in i get a cr of 9.09

i don't know much about head gasket size but if i got up to a .05 thickness i get a cr of 8.91 and a thickness of .06 gets me 8.74

jrp

iTrader: (16)

GM list deck range as 9.235 - 9.245 and pistons out the hole .008. i've seen tha vay from .002 to .010 on stock shortblocks. hence the reason you'll want to measure yours if you want to pin point your CR. also mic the gasket and CC the chamber volumes for precise measurements.

markp03

iTrader: (4)

ok sorry for being such a pain....can you list what a stock ls1 has for...
bore, stroke, head gasket thickness, deck hight, piston top cc's, and combustion chamber cc's

jrp

iTrader: (16)

3.898
3.622
.052, .054, .055, .060 (take your pick as there's never been a 100% conclusive answer). i use .054 myself.
-.008 (oem). i use that, others use -.006 - .007
66 or 67cc (listed as 66.67)
stock pistons are flat top, in your case you'll enter the effective dome volume, this will include 2cc for valve reliefs

markp03

iTrader: (4)

thank you jrp and beast....you guys have been a great help =) i think i got my head on strait and can figure it out!!!!