colt_impala

iTrader: (3)

i found a 2000 ls1 engine for 350 bucks on craigslist. it was already dissasembled, the guy ran out of money and was getting divorced. anyway he claimed it had 18k original miles. everything looks good other than the red loctite on the main bolts and the water marks in 2 walls. also 1 connecting rod was bent a little. i used a little 320 grit sandpaper to get the water mark out after honing.
im assuming the block sat outside at some point. i used feeler gauges to check the cylinders. .0003 fit tight in all but the #1 cylinder. it took a .0004 gauge. is that too much play? should i just bore the block
.0005 and get new pistons, or run it like it is with the #1 cylinder .0001 different than the rest? i dont want piston slap.

LS1-450

iTrader: (33)

Pffft. Are you Kidding? Check it again when it's 25* warmer & it will be .00034". Don't worry about it. I'm surprised that every other cylinder to bore clearance was exactly .0003". If it's really bugging you, put that one in the #3 or #4 bore. They have the best opportunity of running cooler than #7,#8,#1,#2. #7 & #8 because they are furthest from the radiator, #1, #2 because they can run hot if coolant gets low. So, #3 & #4 are the best bet.

Could also be as simple as the cylinder coating in that spot being slightly removed.

colt_impala

iTrader: (3)

So basically your saying run it like it is? Another thing I'm tied on is if I should used forged rods and pistons. And if I only chose one, would I be better to get forged rods or pistons?

98SSClone

iTrader: (2)

What are you planning to do with the engine to justify needing forged parts?

Aside from that information, if I had to choose, I'd go with forged pistons and just upgrade the rod bolts. The factory rods are plenty strong unless you plan on running a retarded amount of power.

Whistler

iTrader: (46)

If you only have .0003-.0004 p/b clearance the engine will seize once it warms up.

LS1-450

iTrader: (33)

IMO, rods first, pistons second if they must be sacrificed. Is forged required? If you are not using spray or forced induction, I doubt it. Also, forged pistons are typically smaller in diameter when @ ambient temp. & are more prone to piston slap until & sometimes after warming up.


Another note: The original response to the clearance difference is written in the context that one piston is smaller than the others & causing the dimensional difference w/ the bore. If in the case that all of the pistons are the same & the bore itself is larger, then the opposite (in regards to warming up) is true & it won't make a difference where the pistons are installed. Regardless, it's not an issue. Has similar effect of whether you use a "30" oil that is closer to a "40" on a viscosity chart or closer to "30" on the chart, in terms of the resulting oil film volume between the piston & wall.

colt_impala

iTrader: (3)

What is Whistler talking about by saying the engine will seize? Am I missing something?
Also I may run nitrous ( no more than a 150 shot) that's my reasoning for going forged.

farmington

iTrader: (14)

Don't you mean .003 and .004 (3-4 thousandths versus 3-4 10 thousandths)?

redbird555

iTrader: (14)

He's saying that because the pistons would expand when the motor got hot and would seize. The bore tolerance on a ls1 is 3.897-3.898 so that is .001 tolerance on a new engine your saying you have .0003-.0004 which is a too tight of a tolerance I'd retake the measurement and get back with us.... Why not just get a bore gauge and measure the whole cylinder to see if its in spec.

colt_impala

iTrader: (3)

But if the motor was running before it was tore down it should be fine now, shouldn't it?

colt_impala

iTrader: (3)

Yes, farmington your correct. That was a mistake in my typing. The measurement is .003 and .004.

Whistler

iTrader: (46)

I was just being a wiseass about the clearance, I figured you meant thousandths instead of ten thousandths. What method did you use to measure the difference?

I'm concerned with you sanding your sleeve after honing.. how much did you sand? Can you post a pic? I'd hate for you to get it together and have one cylinder not seat the rings correctly.

colt_impala

iTrader: (3)

I can post a picture in a day or so, the blocks at my shop right now which is 20 minutes from the house. Machinist said it wouldn't hurt anything after looking at it. I didn't get the crosshatch right so I payed him to redo it yesterday using a 320 stone