Y2K WS6

iTrader: (33)

Ok, I"m building an LS1 for boost, Have already torn block 99% down.

What machine work will I need to get done.

hot tank the block to clean it obviously... magnaflux?? i know what this is on older engines, but an aluminum block isn't magnetic....

Sticking with stock cubes. the engine block has about 155,000 on it still ran good when it was disassembled.

What do i need to do to balance the crank? Do i balance pistons, etc seperately and just have the crank, fly wheel, and balanced. or does it all need to be done together.

The reason i aske these questions is I'm a newbie to the internal engine world, and the "experts" as they proclaim themselves have conflicting statements. everybody around here STILL seems afraid of LS1's.. "them damn computer engines"

I'd appreciate any help on this matter.

Thanks!
Steve

gectek

iTrader: (2)

you cannot magnaflux non-ferrous (meaning no iron ie alum) materials. maybe the liners, but that is it. if its an iron block, its not an LS1. you should make sure its stripped all the way not just 99%, because every bit is going to be extra for the machine shop to do, and labor isnt cheap.

fast01

iTrader: (16)

First gather up all of the parts you're going to use. Pistons for these engines seem to run between .003"-.008" oversize for off the shelf parts. The machine shop will need the pistons to hone the bore to size. Make sure the shop has a torque plate for the LS1. You say the local shops are "afraid" of the LS1, so they may not have what's needed to hone one properly. I've heard you can use a small block Ford torque plate, but I'm not sure on that. Get yourself some ARP main studs and have the block align bored with the new studs installed and depending on the gasket you're going to use and the condition of the deck surface, maybe a light cut on the deck to clean it up and produce a good sealing surface. As far as balancing goes, the shop's gonna need everything from the balancer to the flywheel/flexplate. Bring them the crank, pistons, rods, pins, rings, bearings, everything. All of this stuff will affect the bobweight and will need to be present to properly balance the rotating assembly. I don't think magnafluxing is necessary unless you suspect a crack in one of the sleeves. I'm sure I left something out, so hopefull someone else will chime in!

Y2K WS6

iTrader: (33)

well it was 99% because i was finishing it. it's now 100% stripped

does 250 sound about right to balance a rotating assembly?

thanks guys

fast01

iTrader: (16)

Yup, $250 sounds about right to me.

Y2K WS6

iTrader: (33)

I'll need rings on the pistons too correct? and them fit to the cylinders ( Filing to fit will effect SOME weight)

fast01

iTrader: (16)

You don't need the rings on the pistons, you can't file them until the bores are finished. Besides, the amount of material removed during the filing is insignificant and won't affect your balance. The shop will need them though to get the proper bobweight.

Y2K WS6

iTrader: (33)

What is bob weight?

The rod piston assembly? how close do they get it to the ounce? gram? etc.

jmm98LS1

iTrader: (28)

This is in fact true, we used a SBF torque plate on my 6 liter.

fast01

iTrader: (16)

Your pistons and rods should all be within a gram of each other. Keep in mind we're comparing piston to piston and rod to rod. The pistons do not have to weigh the same as the rods. Also, the big end and small end of the rods must be weighed seperately and equalled in weight matching big end to big end and small end to small end. Once we're all equalled out, we need to calculate the bobweight. Calculating bob weights isn't too difficult, but it is necessary to properly balance the engine. Here's a list for determining bobweights for balancing. This is based on an internally ballanced engine. Things change a little bit when you're going external as the flywheel/flexplate and balancer come into play, but for our purposes here and the way our LSx's are generally done, this will cover you.

Rotating Weight:
Big end of rod (including fastening hardware)
Bearing
Oil (normally estimated at four grams)

Reciprocating Weight:
Piston
Wristpin
Pin locks (if used)
Small end of rod
Piston rings

Bob weight = Rotating Weight + Reciprocating Weight x .50

Once everything is equal and the bobweight is determined, weight is added to the rod journals equalling the bobweight that was calculated earlier. A balance machine is used to specify exactly where the crank needs to be re-worked to bring it into balance. This is done by adding or removing weight from the crank in specific places as determined by the balance machine. To remove weight, the shop will generally drill holes in the counterweight. To add weight gets real expensive real fast. Most crank manufacturers can supply you with a "target bobweight" for their cranks helping you try to pick properly weighted parts to avoid the expense of adding weight to the crank. Shops will add weight in one of two ways. One is to drill a hole in the bottom of the counterweight and press in a slug of "mallory metal" (a tungsten alloy 1.5x heavier than lead and real expensive) and weld it in place so the reciprocating force can't throw it out. The second is to drill a hole parallel to the crank centerline in the counterweight and press in a slug of mallory. The position of the slug keeping it in place. In external balancing, weight is added and removed from the balancer and flywheel/flexplate instead of the crank.

Well there's my long drawn out post to answer a simple question. I hope this helps you to understand how things work and will help you in picking the proper parts for your build. Good luck!

Y2K WS6

iTrader: (33)

wow, thanks for the awesome explanation, so balancer and flywheel and flexplate generally aren't balanced with the LS1 engine?

Thanks the info is helping me a great deal i'm pretty green to the whole internal engine world and have read a couple of online tutorials/info articles i mainly want to know what a shop SHOULD do and for my peace of mind how it's done.

Steve

mike13

iTrader: (27)

If you have the pistons and rods balanced is it required on a 6200rpm motor to have the rotating assembly balanced together? I know for the best possible result it should be but is it required?

fast01

iTrader: (16)

Y2K WS6, No problem! I'm glad I could help and no, the flywheel/flexplate and balancer or in this case more appropriately, harmonic damper, are not altered to achieve balance on an LS1. However, the shop will generally want you to bring them anyway.

mike13, If you know the target bobweight of the crank and your reciprocating weight is within a reasonable margin, you can get away without getting it done. This is basically how it's done at the factory. However, if you are too far off, you run the risk of hammering the bearings and possibly causing damage to the cylinder walls.

mike13

iTrader: (27)

This next fall I was going to install ported heads and katech rod bolts (motor in car) I was thinking it would be nice to just drop in forged rods/pistons because the motor would be torn down that far anyway. Doesn't sound like I can do it without having the crank out to have it all balanced.

Y2K WS6

iTrader: (33)

the question is how long will your motor last.

think about palancing a wheel out of balance it is bouncy if you put the pistons etc in you need to balance it. don't touch the bottom end just do the top and your engine will be fine.

"since i was...." is how i got into this whole build.

fast01

iTrader: (16)

"Because the motor would be torn down that far anyway"

I've spent more money based on this statement than I care to admit. It always sounds good at the time, but by the time all is said and done it always costs at least double what I planned on spending and that's before all of the nickle and dime stuff! All I can say is plan carefully and stick to the plan. If I actually practiced what I preach, I'd have be a lot richer right now! Good luck!