derotoredFD

iTrader: (5)

So I'm a total noob, I know. I already put together a head/cam package for my ls2 using ls3 heads, ported l76 intake, spec'd cam(226/234 .598/.612) and supporting valvetrain. I wanted to put the ARP rod bolts in and found out that you have to resize the rod ends from the torque distortion. My initial plans were to leave the bottom end completely stock except for the ARP rod bolts, but I did a compression test on the motor stand and found that my # were all over the place. Looks like a have 3-4 bad cylinders, so now I have to rebuild the whole thing.
Now I need new piston rings, and with my cam I may need to flycut because I'm cutting the heads .024" to raise compression on the 821s. I started adding it up and 350 for flycutting at the machine shop, 150 for rings, and 80 for re sizing the rod ends is $580 just to make the stock junk work. So I'm thinking about new pistons and rods now instead, even though it's overkill for just a head/cam. I guess I can spray without worry though haha.

So I know nothing about LS bottom end stuff. I have a very limited budget can't afford a stroker rotating assembly right now. I just want to drop pistons and rods in the block for security, and to avoid paying flycutting and resizing. I want stock compression pistons and rods that will work with my factory ls2 crank. This way my head/cam package will still work nicely.

I found this piston/rod set on ebay, will it work for my stock ls2 setup? It says 402 in the title, but the bore is 4" and rod length is 6.125". What is stock ls2 rod length? Are SLP internals any good?
http://www.ebay.com/itm/SLP-Manley-4...sories&vxp=mtr

If these don't work, what cc piston and rod length do I need for my stock crank? I'm guessing that the -6cc on the piston above is from the valve reliefs which is fine. It would hardly lower my compression right?

Thanks for the help,

Ryan

machinistone

You need 6.125" rods with a bushed upper + a set of ~1.314" compression height pistons.

The Scat Pro I beam 7/16" capscrew rods are the best bang for the buck that you'll find. The small end bushing and the big end sometimes need to be kissed on the hone to bring them to size, and you need to stretch the bolts properly because the torque spec that Scat gives you is always WAY too low.

The Mahle Powerpack piston sets are the best for the dollar on the piston side.

Take your block to the machine shop so that they can check the bore size and hone the block, make sure that they will be torquing the mains and using torque plates.

Those SLP piston/rod assemblies are a great price, but they appear to be 1.100" compression height for a 4.0" stroker crank.

bww3588

iTrader: (49)

No need for 6.125 rods.

Run a stock cd piston with stock length rods and call it done.

I went with pistons for a 6.125 rod with a 6.100 rod in my setup due to machining. The rods I went with are the stock length scat rods with arp 2000 bolts. I went with wiseco pistons with valve reliefs for the ls3 heads. The cost of the rods, pistons, rings and rod bearings came in just under a grand shipped to my door.

1nasty86

iTrader: (63)

I would do the mahle pistols and scat 6.125 rods.... on my Ls2 I went with wiseco pistols and scat 6.125 rods and they have worked great so far

machinistone

There's nothing wrong with doing that, but it limits your options down the road due to the non-standard rod length and pin size. If you're going to spend the money on good rods, get the ones that have the most available piston choices.

bww3588

iTrader: (49)

I know if I stroke it, I will need longer rods, and I could have put custom pistons in it to work with the longer rods, but with a 9.2155 deck height, I had to work with what i had.

Pin size is standard small block Chevy .927 which is standard on most aftermarket pistons for these ls engines. So nothing out of the ordinary here.

derotoredFD

iTrader: (5)

So what is the advantage of using the 6.125 rods over stock length rods? What is stock length for rods? Where did you buy everything from, that is very reasonable. I could pull under a 1k, but $1400 is out of my range. Too bad those SLP pistons/rods are for a stroker crank. The problem is if I got a crank that would mess up my cam specs and I already have the cam.

bww3588

iTrader: (49)

The stock length is 6.098. The 6.125 rods side load the pistons less with a less extreme rod angle. They are a must for stroker cranks for piston to crank counterweight clearance.

I got my rods from ws6store.com for less than 300 shipped to my door. Pistons and bearings came from HKE for 670 shipped to my door.

derotoredFD

iTrader: (5)

So the difference between 6.098 and 6.1 is negligible I guess, it seems that no one makes them in 6.098. Well I have the rods figured out, but what about the pistons. The highest CC they make is -4, and with factory heads that would drop compression to 10.5:1 from 10.9. So even if I mill the ls3 heads .024" then I will be at 10.4 instead of 10.8 like I wanted(if its that easy). How can I get the compression back up? Do they make a piston that is same cc as factory but with valve reliefs still?

Thanks for the help so far!!

derotoredFD

iTrader: (5)

So it seems pretty common for a piston to be made for 3.622" stroke and 6.125" rod length, why not use a 6.125" rod if it offers less side load on the piston? Will there basically be no difference at my power level? What is the max power level that the mahle pistons, scat rods, and stock crank will safely take at the wheels? I won't be near it probably, but if I ever decide to add a blower it will be good to know.

bww3588

iTrader: (49)

Not without a dome. Just mill your heads a little more.

machinistone

Ah, ok - I figured you were talking about the 6.098" rods with the .943" pin.

The difference between a 6.098 and a 6.125 will have no effect, you use whichever one will allow you to get the piston you want and end up with the proper assembled height to match your block.

Those parts will handle over 700, issue is that you need to set up your ring gaps for boost at the time of the build. Additionally if you're going over 12psi or so you want a steel ring and a 2618 piston.

Diamond has pistons in the 10cc dome range which would put you where you want to be on compression without decking the heads.

derotoredFD

iTrader: (5)

I didn't consider a dome, thats smart. The problem is I will need a piston that matched the ls3 heads if I get a dome right? I was wondering about that, since the LS3 heads have bigger valves, won't I need valve reliefs designed for ls3/l92 heads?

How do you know 10cc is what I need on the piston? Is there a compression ratio calculator somewhere so I can play with these numbers?

derotoredFD

iTrader: (5)

ok Guys, so check this out. I found a calculator here on the forums and started playing with it. It looks like I can leave my heads unmilled at 70cc and get a +4cc dome piston and that will get the 10.8:1 compression I'm looking for.

Wiseco makes a +4cc dome piston that is designed to work with the stock rods(don't know why you would want the stock rods), and SCAT makes a rod with a .944" wrist pin, but the pistons have a .943" pin. Do you think these pistons will work with these rods? This combo would be perfect for what I am trying to do. Please give input!

Pistons
http://texas-speed.com/p-771-wiseco-...22-stroke.aspx

Rods
http://www.ws6project.com/user_stor/...olts-944-pin-/

bww3588

iTrader: (49)

Should work fine as long as the rods are bushed for a floating pin. The pistons have a smaller pin because they are not for press fit rods.