TableLeg

I'm looking at fitting new stock pistons. Should I try and source GM ones or are there any other alternatives?

Only NA, max 400Bhp at the flywheel.

G Atsma

Check with Summit or WS6store.

swathdiver

Stock will be fine at that power level, forged would be nice too.

TableLeg

Thanks for the reply,

I see Summit do some but they're not GM ones. Dint know much about the different brsnds to know what's good and what isnt.
sent emails and messages to WS6 store but never received any responses unfortunately. Shame as I've used them before as I have Summit too.
These are the ones on the Summit site.
https://www.summitracing.com/parts/s...make/chevrolet

TableLeg

Thanks for the reply.
I'm struggling to find the stock pistons (don't know what the part number is) butvI can find all sorts of compatible ones made by different brands. Just don't know enough about the brands to know what are good and what aren't.

TableLeg

Also I figured if I used stock pistons and weight matched them to the removed one I wouldn't need to rebalance the assembly.
I could maybe do that too with aftermarket ones but I guess that would depend on how close they were to the originals weight.

swathdiver

A Gen IV flat top piston is 89060486. Mahle was at one time, might still be, an OE supplier of LS pistons.

stockA4

I've done this before It's super easy, find a used set of 4.8L Pistons and swap them onto your connecting rods. No need to rebalance no need to worry, New rings if it'll make you feel better. The 5.3 tends to wear the piston skirts where the 4.8 does not, so if when you pull out the old Pistons from the 5.3 and the skirts are worn pretty bad don't worry about it

​​​​​​I used a cheap press from harbor freight to push out the old pins, then all you need is a small propane torch to heat the rod ends and fit the 4.8 l Pistons on your rods.

You've heard what kind of power people have made before with the stock pistons right?

TableLeg

Many thanks for the reply and info, I'll go check it out now.

TableLeg

Many thanks for the reply.
The L33 has the Gen IV rods and pistons so the pins are held in with small rings, no need to press them out.

The only wear marks on the piston are indeed on the skirts.

TableLeg

No, do tell me.

I wonder if I should clean them up reuse them... if so, new rings?

TableLeg

Given the choice between stock GM pistons and alternatives is it worth using Hyperutectic ones with the coated skirts instead? Just wondering if the small extra cost is worth it?

For example
Gm ones $278 plus shipping
Speed pro Hyperutectic from Summit $335
https://www.summitracing.com/parts/s...make/chevrolet

Both need rings as far as I can see.

I'd never heard of Hyperutectic until recently but from what I've read they seem like a good option.

Any thoughts on this?

Che70velle

iTrader: (6)

Show us some pics of the pistons you took out. Skirt wear is normal, especially with cast hypereutectic OEM pistons. They are setup to run very tight clearances, which makes the engine quieter and more efficient, so skirt wear is completely normal and they will last for hundreds of thousands of miles. New pistons are pretty to look at, but you can’t see them once in the holes. Plenty of guys run north of 1k hp on stock pistons with boost and the right ring gap.
What are you doing with the engine? Is this a stock rebuild, or are you going to mod it? Boost? Give us some info please.

vht

Have you tried Rock Auto? They should have several brands of stock pistons.

G Atsma

As long as you get STOCK-SPEC pistons, it doesn't matter who makes them. GM does NOT make their own pistons. Mahle is one of the suppliers, as was mentioned above.

TableLeg

Many thanks for the reply 👍🏻

I'll put some photos up later today of the pistons.

To answer your question about what I am doing with the engine, I bought it used with no knowledge of its history. I fitted new head gaskets, heads refaced plus 3 angle valve seats cut, Pac 1211X springs and stem seals fitted, new pushrods, a mild Comp 212/218 cam, an LS6 oil pan plus LS6 intake and injectors.

The plan was only to fit a mild cam but the other things seemed worth doing at the time.

I have no plans to modify the engine more than it is now. The engine is in a lightweight road car and my hope with the above was to make 400 Bhp at the flywheel (which I believe should be possible). It made 373 Bhp before the cam change.
On remapping for the new cam I was getting detonation (the mapper told me) and he pulled the timing until it stopped and I cam away with less power. At the times he said it was detonating I did see a puff of white smoke from the exhausts. Searching this up there seemed to be 2 likely causes, oil stem seals or piston rings. As the stem seals had been replaced already I figured it could therefore be the pisthis and/or rings so pulled the heads off and removed the pistons and rods.

TableLeg

G Atsma

Mucho scuffitude.....

TableLeg

New pistons???

Most of them are the same amount of wear.

1FastBrick

iTrader: (16)

They don't look that bad. If your really concerned you could have them re-coated...

But Guess what is going to happen after you get it running? The new coating will end up doing about the same thing...