I just picked up a basket case LS1 engine and when got it I didn't notice these small scratches. is this block shot or are they not enough to worry about?

can u catch your fingernail on them. and has the block been bored the 10 thousands yet.

As stated as long as your finger nail doesn't get hung up on it you can just give it a quick hone. If it's a virgin bore you can always get away with an overbore.

Agreed. It is hard to tell how deep they are but if they are super shallow (fingernail doesn't catch) than a ball hone might be all you need. If I owned that block I would go for the overbore (Alum LS1 motors can only take a tiny overbore - .005). IF you are not going to use the stock pistons you might as well have a shop take a look at it and prepare for an over bore.

Why can the aluminum motors only take a small overbore?! I thought they were sleeved from the factory?

i thought that the early blocks could only go .005 and the later blocks could go .010.

1997 and1998 blocks to .005 and 1999 and up .0.10

They are sleeved, but the sleeves are thin. One92RS is correct on his bore sizing. The Iron blocks can be overbored more (.030) and do not have sleeves. The aluminum 5.3 blocks can be bored up to the same bore size as a stock 5.7 LS1. Max bore on an aluminum 5.7 block is 3.89 IIRC.

A couple of the scratches catch with my fingernail. I don't believe this block has been bored out yet but I am not positive. this is supposed to be a 99 block but I haven't checked the casting numbers yet.

so basically my option is to take it to the machine shop for them to check it and hope like hell it hasn't been bored already?

Yeah pretty much, unless you have a micrometer you can check it yourself and get a rough idea.
If it's been bored already and you don't plan on making huge power you can always just give it a hone and get new rings... (I'm sure somebody will yell at me for suggesting this).

Edit:
and I never knew that about the LSx blocks. Thanks for the info.

Its not worth your time and money to build an engine with less than perfect cyl walls. A fresh engine with blow-by will only get worse

To the OP, you might want to start looking for another block. Sleeving is always an option, albeit expensive, more-so than a new block

wow.. guess i got screwed. paid 800 for this engine.. if the block can't be bored its a freaking boat anchor. at least i got the heads, crank and assorted other parts out of the deal.

using a standard bore gauge and calipers my cylinder bores are measuring 3.897 to 3.901 (variance due to human error i assume). I'm hoping this means its a virgin block and can take a .005 overbore to clean those scratches.

thank you all for your advice. sometimes this car hobby seems to be a long chain of "lessons learned the hard way" but all in all i still tend to enjoy myself.

just looked up my block number:
12562174...350...98-up...crossbolted block, Gen.III, "LS1", aluminum


is this one that can take the .010 overbore or only .005?

i would recomend taking it to a shop, and having them mic the cyls also.

you will have to get that checked. only 99 up blocks can be done .010. but .005 might clean that up.

where are you located? was it a bare block you paid 800 for?

Their are a few reasons you are getting different readings; human error, ovaled cylinder walls; wear and tear in general and even a difference in temperature (the rate it expands and contracts at I have been told can change as much as thousandths (.001-.009) of an inch.

If you have no prior experience to using a micrometer on something like a motor, bring it to a shop and let them give you their opinion.

I'm located in northern NY state.. picked it up in maryland. 800 included: block, heads&valve covers, intake w/ injectors, 2 ecms, crank, 16 rockers, 16 roller lifters, new headbolts, new crank and cam bearings, full ac system (compressor, lines, condenser), water pump, oil pump, pulleys, timing set, most sensors, TA oil pan with pickup, stock exhaust manifolds, vacuum lines, 2 ac accessory brackets, an odd looking pump I havn't identified yet, both coil sets, throttle body, etc. here's some pictures:













was that a decent deal?

Two of the connecting rods don't look like the others...very likely something very bad happened.

one piston, two rods are different. but with this being the leftovers from 2 engines, no idea whether it was this one or not. there are no gouges or any other signs of catastrophic failure.. just the previously mentioned tiny scratches.

As mentioned you have two new rods and one new piston... that's a bad sign and a big no-no. If you replace any pistons or rods you should be replacing them all; heck even you reuse rods you are supposed to mark what cylinder they came out of!

If I recall correctly the 853 heads are only used in 1999 and up which means chances are good you can go with a .010 overbore as long as those are the heads for that block.

Your crank also looks scratched.


More pictures from different angles might help. Personally I'd hone it, reassemble it with just the parts you have and sell it

I'm thinking the 'odd looking pump' you haven't identified is the egr valve.

I would say thrown rod since the scratches are perfectly vertical, but that doesn't explain how they got all the way up to the top of the cylinder wall.

nope.. its not the egr valve nor is it the air pump. it doesn't look like a power steering pump, but it has a small white/clear reservoir. Its still in the box with my emissions crap and ac system.. i'll pull it out and snap a photo tonight.

Here are the photos.. any ideas?

Don't go by the heads since you have the block #. Especially with a basket case.

853 heads were used in '99 & '00. Late '00 got 241's.

Hydra boost steering pump?

i believe that is a power steering pump.

i don't see the scratched crank? honestly I think these guys are trying to scare you. I would take the block to a machine shop and get a good opinion. once you get that you can go from there. I don't see anything that would not run fine in a stock car and be just fine but picture wont show damage for what it is.. sometimes it hides damage a little other times it makes it look worse

its not the crank that is scratched it is the cylinder walls. that needs to be addressed. no since in going thru all that is involved in a swap such as this just to have a problem that can be fixed now.

The cylinder wall scratches don't look significant to me. But, you should have them looked at by someone who knows these engines.

Ditto the rods, pistons, and main caps. Basket cases scare me, never really know why they are in pieces.

That doesn't look like an LS1 power steering pump (LS1 PS pumps aren't splined, for one thing). Might be an LM7 or LQ4 pump (I gave my LQ4 pump away, don't remember exactly what it looked like).

Trucks use the same style PS pump as 3rd gens did stock. That pump isnt from a 3rd gen