gboy

Dropped my LS1(5.7) block and crank off at my local reputable machine shop. We discussed him building my short block with my supplied new parts and he stated he would only do it with a minimum .005 over pistons. I agreed since I was thinking of buying Wiesco Tru Pros(can be had for a good price and come in a 3.903 bore). After he cleaned and inspected the block we talked again and he's saying I need 3.905 pistons(tru pro's don't come in as far as I know) for .005 over. He didn't mention the bores were scored and they didn't seem to appear it to me. Am I missing something? Are LS1's not 3.897-3.898 bores and no I didn't check the bore before hand. I don't have a bore checker and I suck at checking holes with calipers. The previous owner said it was never bored/honed. If there's a sticky or thread that covers this point me in that direction. I do remember coming across a thread in the past where this was covered and IIRC the consensus was some machinists think it's a 3.90 bore. Any info/advice/opinion about this would help.

Just in case it matters, this engine is being built for 10-15lbs of boost/stock crank/budget forged rods & pistons on 91pump

bammax

You don't bore an LS1. You hone it or you have to replace the liners which is a huge deal.

RonSSNova

iTrader: (3)

3.898 is correct. Your 3.903 pistons should meet his desire. Unless he says the bores won’t clean up with a .005” hone job.

Have you looked into the Mahle kits?
Very nice parts. Not sure what oversize they make for the LS1.

I just bought a set of stock bore for a project. The block I scored only had 28k miles on it.

B52bombardier1

Are your cylinders tapered or out of round from wear? That might explain his concern.

Rick

gboy

He specifically said he wouldn't hone them, only overbore at least .005. No mention of taper/out of round during second call. So, obviously I'm calling him come Tuesday and catch him before he takes a cut on the block. Hoping this a big misunderstanding.

Ron, I'll check out the Mahle pistons and I'm seeing them for not a bad price(under 650). The Wiescos are going for under 6 with rings/wrist pins, but it seems they come in 3.903 and 4.0+ bores only.

I know a lil" about machine work and everybody I know is either ol' school SBC/BBC or they did a turn key swap. Just needed some opinions/advice from people who've dealt with these motors. Thanks for your input.

Just in case, can anybody recommend a machine shop in the East Bay/Fairfield/Stockton/Tracy(Ca) area?

BigBlackCamaro

Bore, whatever you want. He's not dumbing down the conversation for you. (which is good)

There no reason to not bore it to .001 under final size, then hone it to fit the pistons.

This is what my machine shop does. Bore it to clean up, tell me what size pistons to get, hone it to specs of the pistons.

If you don't know, no one bores a block and then uses it. Every bore job needs a final hone.

Che70velle

iTrader: (6)

A .001 hone would be a makeshift job, at best. Might feel smooth to the touch, but wouldn’t be anywhere near right. The valleys that the boring bar leaves behind are .005 to .006 deep. My shop hones .006 to .007. I’ve seen a .005 hone under high magnification and it’s still rough. Hard on the rings. Most shops that I’m familiar with will hone the LS1 .005. No boring necessary.

6.0 Impala 64

I have a new Mahle Powerpak with 3.898 pistons I want to unload and you wouldn’t need to get your bore re sized.

part number: LS1340898F04

gboy

Sorry about not posting earlier.

Stopped by and talked to the machinist. It seems there was lil bit of a communication error on both sides(something like "Who's on First?"). He prefers to go 3.905 in case of taper if he is assembling the short block and it turns out I can't use the Wiescos(can't get the CR below 10:1 with my heads/requires stock length rod) So, I picked up Mahle PowerPak kit in 3.905 that puts my CR in the 9s for under 650 and they're having a rebate on certain part#s til July which puts them under 600. Thanks again everyone for your info/opinion and sorry if I wasted anybody's time.

RonSSNova

iTrader: (3)

Good deal. Good luck with your build.