Reuse stock pistons

**redbird555** · 11-17-2010, 04:12 AM

Hi guys I'm trying to plan out the costs of a stock ls6 rebuild for my ls1. MY current ls1 engine has 117k on it and honestly runs great just the normal piston slap but it doesnt burn any oil. I just do a lot of road trips and have the parts to do an ls6 conversion so over this next summer I'm thinking about just pulling it and doing a refresh with bearings rings etc to go along with the ls6 cam and heads... My question is on every stock rebuild I have seen I have reused the stock pistons or stock sized pistons as long as the engine didnt need an overbore just a quick ball hone to clean it up then reinstall and never had isssues. However I'm told that with the ls1 I'm better off replacing the pistons even if a hone is done and have them sized due to the piston to wall tolerance? Is there some special case here or are people simply being a little over cautious?
Ive had the engine apart once before at 100k to do a head gasket and I could still see the cross hatchings in the cylinder walls so I doubt much honing would even need to be done like I said above Ive seen engines that were ran into the ground then simply rerung and ran fine. So im kind of stumped here, I mean it is a different engine but its still just a small block chevy???

**Spaz** · 11-17-2010, 04:22 AM

to be honest the ls6 cam will give minimal gains... i would replace them and try to bump my ocmpression up for some more HP...

**Smittro** · 11-17-2010, 04:23 AM

@ 117k first thing you'll need to do before buying anything is have the block checked and preped.. Check for cylinder out of round.. With 117k my guess is there will be some out of roundness to the bores.. If the "down side" of the piston skirt is worn smooth I'd replace the pistons.. The grooves on most pistons skirts are there to aid in oiling the cylinder wall.. Could possibly have cylinder wear issues later if you reuse them.. But people do reuse them with nary any trouble.. I would also replace the stock units if you're going to be building more than stock power especially.. Ring lands could be overly worn or weak and cause a whole new set of problems in a new-ish motor.. IMHO too touch and go to not replace..

**Spaz** · 11-17-2010, 05:38 AM

might possibly be cheaper to just build up a 402 block but you said you already have all the items needed...

**redbird555** · 11-17-2010, 08:31 AM

I know the ls6 cam isnt the greatest thing for hp numbers however the car is an auto, my daily driver for long trips and I really dont wanna stall it. And from all the research I have ever done a stall is need to get a car to drive right with even a mild cam, I supposed I could contact Geoff or Patrick G and ask them to spec a custom cam for a stock stall but at that point a custom cam is 400 bucks and then I'd have to figure out if the gains would be worth it since the gains with such a small cam would probably be minimal. Like I said aove the car is a DD so building a 402 which is already 3k ish for the short block would be way to expensive not to mention the parts need to beef up the transmission and rear end. At 117k I do plan to have the block checked for bore roundness and I'll keep in mind about the groves on the skirts. I may have a lead on a low mileage ls6 short block for a good price but we'll have to see if its available when the time comes along. If worse comes to worse I'll have the block bored 10 over and get new pistons when I order the rebuild kit. I was hoping since the engine didnt have any issues currently and it still looked good I could get away with just a freshen up, deglaze the cylinders with a flex hone and reinstall the pistons.

**Jay37** · 11-17-2010, 07:50 PM

Originally Posted by redbird555

I know the ls6 cam isnt the greatest thing for hp numbers however the car is an auto, my daily driver for long trips and I really dont wanna stall it. And from all the research I have ever done a stall is need to get a car to drive right with even a mild cam, I supposed I could contact Geoff or Patrick G and ask them to spec a custom cam for a stock stall but at that point a custom cam is 400 bucks and then I'd have to figure out if the gains would be worth it since the gains with such a small cam would probably be minimal. Like I said aove the car is a DD so building a 402 which is already 3k ish for the short block would be way to expensive not to mention the parts need to beef up the transmission and rear end. At 117k I do plan to have the block checked for bore roundness and I'll keep in mind about the groves on the skirts. I may have a lead on a low mileage ls6 short block for a good price but we'll have to see if its available when the time comes along. If worse comes to worse I'll have the block bored 10 over and get new pistons when I order the rebuild kit. I was hoping since the engine didnt have any issues currently and it still looked good I could get away with just a freshen up, deglaze the cylinders with a flex hone and reinstall the pistons.

For sure man, if everything is within the factory specs, hone it, run it.

**Firebirdjones** · 11-18-2010, 07:13 AM

Nothing wrong with the LS6 cam really. There are more people out there using it than you know. It passes smog, runs smooth, good mileage, and still makes decent HP. Stock LS6 engines generally put down 370+ RWHP, nothing to sneeze at and will put a 3,600 lbs. car into the mid 12's at 112 mph easily. It puts the smaller and lighter vette into the low 12's (even high 11's) at 114+ mph.

On the honing, I'd leave that up to the machine shop and what they find. If you already have piston slap, and you want to hone and reuse,,,,then that problem isn't going away, and may even get worse. At 117,000 miles I would keep an open mind and be prepared.

Remember the tighter a piston fits the bore the better ring control you have. Better ring control means more power. Which is why you see some pistons today fitting as tight as .0015. Back in the day most forged pistions called for .004 to .006
Ring control is even more critical in engines that run small ring packs,,,,such as these LS engines do. I believe they are 3mm. Smaller ring packs mean less friction and more HP, but it comes at a price.

**Jay37** · 11-18-2010, 11:00 AM

Thats good stuff. I couldn't agree with Firebirdjones more. There are alot of guys on here, that seem to have very deep pockets.

**Firebirdjones** · 11-18-2010, 12:32 PM

I didn't mean to sound that way, I'm all for saving money if it makes sense. But I sure don't want to save a few coins if there is a possibity of it coming back to bite me and cost more in the long run.

117,000 miles is alot any way you cut it. Most of these LS1 engines can only be honed .005 and that is if the cylinders aren't out of round anymore than that, at which point it's new block time or expensive resleeving. Honing that far anyway will require new pistons.

I've only heard of LS1's being honed at the maximum .005 if they had an easy life and not that many miles (60-70K or less). Higher mileage examples may be too far out of round to clean up at .005
Maybe there are examples of higher mileage success out there, just trying to prepare you.

**Jay37** · 11-18-2010, 01:53 PM

Originally Posted by Firebirdjones

I didn't mean to sound that way, I'm all for saving money if it makes sense. But I sure don't want to save a few coins if there is a possibity of it coming back to bite me and cost more in the long run.

117,000 miles is alot any way you cut it. Most of these LS1 engines can only be honed .005 and that is if the cylinders aren't out of round anymore than that, at which point it's new block time or expensive resleeving. Honing that far anyway will require new pistons.

I've only heard of LS1's being honed at the maximum .005 if they had an easy life and not that many miles (60-70K or less). Higher mileage examples may be too far out of round to clean up at .005
Maybe there are examples of higher mileage success out there, just trying to prepare you.

I agree. The deep pockets quote was not aimed at you, I didn't want it to sound that way. It just seems to me like there is alot of guys on here, recommending pro-stock type parts in a street car. I would never recommend some one put something together that is not in spec. I just have had very good luck with GM v-8s. Just saying measure and inspect the parts, before getting the wallet out. If they are bad you don't need to replace them with better than GM parts. We all know it can be a vortex that sucks all your money in when you start trying to do things better than GM.

**Firebirdjones** · 11-18-2010, 02:32 PM

Originally Posted by Jay37

I agree. The deep pockets quote was not aimed at you, I didn't want it to sound that way. It just seems to me like there is alot of guys on here, recommending pro-stock type parts in a street car. I would never recommend some one put something together that is not in spec. I just have had very good luck with GM v-8s. Just saying measure and inspect the parts, before getting the wallet out. If they are bad you don't need to replace them with better than GM parts. We all know it can be a vortex that sucks all your money in when you start trying to do things better than GM.

I understand and agree completely

**redbird555** · 11-19-2010, 05:24 AM

Thanks guys I'm def gonna have the bores checked after all it'll be at the machine shop to get cleaned and checked for cracks so checking the bores makes sense. When I had the engine apart to do the head gaskets I couldnt believe the shape it was in. The bores had no top ridge in them and the walls still had the cross hatchings in them this was only about 10k miles ago. And ya like stated above the car does slap but doesnt really burn oil so I'd think the rings are ok now if the bores are within a reasonable spec and just a flex hone is done does anyone think the slap will get worse even just a hone to deglaze the walls?

**Firebirdjones** · 11-19-2010, 12:21 PM

A quick hone for new rings just to knock the glaze off doesn't remove that much material. I don't think it would change your situation of piston slap.
As long as the bores are still nice and round you could get away with it.