NJ_phil

Car has a stock bottom end LS3, 3400 miles, still has visible cross hatching on the bores. Dyno'd @ 780 but didn't have the nerve to push boost above 12psi, spark > 14 and AFR < 11.4. Runs super strong and not looking 1000hp, just that it feels like I'm driving a time bomb after reading about fried pistons and broken lands destroying motor.

Generally looking to build more safety and strength into the motor in case I move to a bigger blower or go to a small shot on N20. Car just sits in the garage in-between car shows and cruise nights and I'm getting bored with it.

Is it just a matter of sliding a new set of rods and pistons down the holes after a light re-honing with a ball stone?. No extra machining? balancing or clearance problems with same stroke and bore size?

Mordeth

Heya Phil,

First thing you should do is a leakdown. This will give you a good idea of the health of the cylinders, rings and pistons. Very easy procedure. Next would be to either put a borescope through the sparkplug holes and take a peak ($30 on Amazon and takes 5 minutes) or pull a head and look at the piston crowns and cylinder walls. See what is going on there. You won't be able to do a full inspection, but it will give you some idea of what if anything is going on.

As for new bottom end: Are you going to replace with stock or aftermarket forged? If going aftermarket, then the weight of the rods and pistons will be different than what is coming out and you will have to re-balance the entire rotating assembly. You will also need to make sure you have the correct bore and stroke for the cylinders, and know which rings are being used, the valve reliefs, etc. It will take some research and you shouldn't just "drop" a set of pistons in. The rotating assembly is a system.

NJ_phil

Probably should have explained that motor is perfectly healthy at this point. I get a few drops out of the catch can between the valley and intake every few hundred miles and haven't seen anything at all in the catch can that vents the rockers....absolutely no blowby at all. sure compression is still fine.

Already had a borescope down the cylinders and noticed a lot of carbon from the previous owner who never drove the car hard and also noticed what looked like some recent pitting on the pistons since I've been running it under boost. Possibly from the carbon burning off under boost causing hot spots or something....ran a bunch of E85 to help clean things up and carbon deposits are better, pits in pistons are only visible under 10x magnification on the borescope.

Point is I have no confidence things will continue to hold together under boost at high rpm and I do like to beat on the car in between car waxings.

I was hoping to replace the rods with something like Callies Compstars or even a forged GM set since I've heard that's a weak spot with boosted engines, direct replacement to OEM but stronger. Also thinking about Forged pistons like Diamond or Weisco, possibly dropping from 10.7 to 10.0 CR, since the OEM HT pistons are also a weak spot. The stock crank should be fine at my power levels and beyond.

Basically looking to replace what I have with a forged set (rods and pistons). No dimensional changes, 1:1 replacements. Pulling the crank out and changing the entire rotating assy. is probably a showstopper and I'd just probably be better off picking up a pre-built forged short block.

0GolenEngineService

upgrading to Callies compstar rods and Wiseco pistons would definitely help in reliability. When changing to these new parts you will definitely have to have the crankshaft re-balanced since your new parts will more than likely be a different weight. Also, we recommend that you have your cylinders honed by a auto motive machine shop. Someone who knows the proper angle of the cross hatch needed for your new high performance rings. You are definitely heading in the right direction for a stout engine.

Mordeth

Understood. I have had my motor out before and am getting ready to pull it again and it is no fun.

If you replace the pistons with a set of forged slugs you will need to balance the crank. The pistons will be most assuredly of a different weight. Same with the rods. All of the pistons you listed are of very good quality, but they will most likely be lighter than what you have by a not insignificant amount. Everything must be weighed and you will likely have to have the crank drilled to remove weight. The entire rotating assembly must be balanced. You should not just drop in replacement pistons. You could actually create a problem when you don't even currently have a problem.

There are also other considerations. The rods have to be correct. The valve relief and piston crown shape on the new pistons need to be correct for the compression you want. If you need to take material from the bore, you will need to make sure you size the pistons correctly. You may not know this until you look. The finish hone needs to be correct for the type of rings you are installing. The cylinder to piston clearance also needs to correct for the type of piston. 2318 aluminum needs more clearance than 4032 because it has almost no silicon and so it will expand. It also has a higher tensile strength. 4032 is more brittle, has more silicon but doesn't expand as much...so you want a tighter clearance. There are other differences as well. So you need to determine the type of aluminum you are going to use.

You could open up a can of worms. Best thing is a leak down test to ensure that you have no leakage. This is a better test than a compression test. Maybe this will give you some piece of mind before embarking on this quest. I am not trying to dissuade you from forging the bottom end. But it is not a quick, easy task and requires a bit of planning, a good machine shop and quality parts that are mated correctly.

NJ_phil

Not going to go the route of pulling the motor and switching over to a complete forged rotating assy since there is nothing wrong yet but thinking about redoing the fuel system (again) to handle E85 long term.

Thanks for the replies