ADOR

After finally getting the right transmission installed and working in my oldest boys 1993 Z28 we cranked the engine for the first time and noticed it had a light tap on the passenger side. We thought it might be a lifter since the engine had sit for a while just being turned over not ran.

The car ran fine from the shop (we had a shop put the trans in so we could have the transmission 3 year warranty), and it was driven from the shop to our house about 13 miles away. About a week and a half later I took the car to the muffler shop to get the exhaust welded back under the car and get a cat re-installed as the car had none. On the way back home I noticed a loss of power and the knock was a lot louder just about a mile from the house.

Since then we have pulled the valve covers and cranked it for a little bit to make sure it wasn't any thing up top and grabbed the rocker arms and shook them them by hand to make sure.

We haven't pulled the engine out yet or ordered anything yet but it looks like it will need a crank replacement due to a spun rod.

From what I have read on here and other places the LT1 uses a light weight rotating assembly (most say weighted more to a 305 crank bob weight than a 350) from one thread it says that the crank/rotating assembly from a one piece rear main seal gen1 SBC will work.

If I don't go with a LT1 crank kit and wanted to go with a SBC Gen1 one piece crank rotating assembly (crank, rods, pistons, flywheel and balancer) would all of that fit?

I have read where the LT1 front balancer is not really a balancer it's more of a dampener. Is that true?

I still need to calculate compression ratio to make sure it wouldn't be too low with aluminum heads with the Gen 1 rotation assembly and that the crank pulley would align up for any accessories.

I am still in the planning stages right now. Before we get anything I will have to pull the engine and make sure it's just a rod, not a main, check cylinder wear, etc.

Anyone else done this kind of swap?

I know some may throw in why not get a 383 kit while you have it down. I have considered it and it's still on the table but it will be my sons first high performance car and is slated to be his daily driver is why I am thinking more 350 than 383.

Current mods on the car are.
stainless BBK headers
3" single exhaust
3" performance cat
160 deg thermostat
electric fan override
K&N cold air intake
Hypertech stage 2 chip

The car originally had a high dollar racing trans in it and the guy I got it from just wanted the trans. He was running a 3500 stall with the stock 3.23 gears and stock tire height. So I think he high reved it all the time causing this problem.

lt1-xjs

The crank may be able to be cleaned up and reused.

Chimera96

^^^

Op, until you tear the motor down enough to clearly identify what the problem was and if bearing is bad causing crank journal damage you "may" just have to have the crank ground down .001-2 under.

If it is so bad the crank needs replacing...I would go find a good used LT1 crank for sale. Send to machine shop for polish 0r .0010 under.

On the LT1 the front balancer is a neutral balanced "damper". LT1 are rear balanced motors with a weighted FW or flexplate

Ananta1369

Quote from Enginebuildermag.com, "350 – The crank for the LT1 looks just like the one in the late 350 and has the same casting number 14088526, but it’s balanced for the lightweight pistons that were installed in the LT1. Be sure to keep these cranks separate so they don’t end up in a regular 350, and don’t ever use a regular 350 crank in a LT1. In fact, if you are short of LT1 cranks and don’t have a balancing machine in your shop, you would be better off using a crank from a 305 instead of a 350 because it’s actually closer to the balance specs for the LT1 crank.

Rebuilding the Chevrolet LT1 Engine - Engine Builder Magazine

ADOR

Thank you all for your replies. I know I won't know for sure until I get time to tear it down in another month or two. Just preparing for the worse and wanted to double check the info I have read.

Ananta1369, I have read that article but that is just for swapping a 86 up 350 crank and using the LT1 Pistons, rods, etc with it. I would be swapping the whole rotating assembly if needs be.

Another consideration is I think the 1993 model has the Chevy "pink" rods and the newer versions use the stronger PM rods.

lt1-xjs

I'd reuse the stock rod, install ARP bolts and have it resized.

Chimera96

^^^ +1

Op, If you do need a crank, get a LT1 used crank. I suspect LT1 builders like ERE and Golen have a pile of them and could even polish or machine it if needed.

Your cyl walls may be good with just a hone and re-ring your pistons.

Ideally your crank is salvageable with just a - grind. New main & rod bearings, rings and rods resized with ARP would be a fresh motor.

Injuneer

Stock crank and rods support 500 flywheel HP. Polished and filleted will only make the crank better. Why increase the weight of the rotating assembly with the 3rd Gen pistons?