Looks good to me. That manifold is cracking all to hell tho

 

??

Where??


Matt, any chance I can get a closeup of an LNF stocker from you guys? Like, straight down the spark plug hole, center of the piston area.

 

I've got them on my pistons.

 

Cool, so it's normal then. Just wanted to verify.

What happend to #3 wall on yours?

 

Stock LNF Piston-

 

It's supposed to be like that, to keep it from warping.

 

Yep looks normal to me. You going to set his ring end gaps a little wider than stock Joe?

 

So its cut like that? They look a little jagged hence me saying cracked.

 

Ok... so those marks aren't there.

Now i'm confused.

 

Scoring.

Dealer says it's within tolerances though when I showed them, and haven't had any issues with it.

I'm planning on eventually opening it up to do some work/mods, so I'll probably fix that then.

 

Always. He's planning on a lot more power, so i'll adjust accordingly.

Between ports you mean? No, they are seperate from the factory. Cuts down on cracking actually.

 

For future reference, how much gap is stock and how much more do you need to add per additional HP goal?

 

Good thinking GM

 

No idea on stock gaps, probably in the low teens. For a baseline, you want to figure about .0045-.0055 per inch of bore size on an average engine (performace). If you plan to run lots of boost, nitrous, or exotic fuels, i've seen up to .0065/in recommended. So for our 86mm bores (3.5in for arguments sake), you are looking from .016 to .028 depending on your specific application, pistons, power goals, and personal preference. There will also be a debate on how to stagger the gaps (whether first or second ring should be the bigger gap), but that discussion is all for another thread. Read up on it a little online, there's a ton of info out there.

 

okay his piston definitely looks different. there is like an extra set of exhaust valve reliefs near the bowl area

 

I see them on Stamina's motor, but not the OEM pic ZZP posted. Possible they are just whacking into the pistons under boost? Pistons are much softer than the valves, and if you were running the car hard at the time when it happened, it's feasible that the piston would just yeild and no real damage would result.

 

There's yet to be a pic where there is evidence of valve to piston contact in this thread. Blazin07ss, pics or GTFO!

 

Maybe the valves are floating a little at high boost. Fabian and Matt were both running a lot of boost. What about Stamina?

 

the only pics i have are the same as joes. i was there when he pulled the head

 

Not possible.

Oh, I didn't realize you guys were talkin about the same motor. Take some better pics!

I know the area that you're referring to, but it just looks like gunk in these pics.

 

Normally, no. Mine usually topped at 22-23psi, but I remember one occasion it wandered up to 26 during an extended run.

 

It is just the angle in the pics.

 

The reliefs are definately there.

The ZZP pic is NOT a stock piston. Look at the bowl area. Stock is round, the aftermarket one is square (ZZP).

 

This one looks square too and its from gm.

 

Agreed. Wonder if the Cobalt LNF has different pistons for some reason?

Tag for that pic says sky redline.

ZZP, was that piston a FWD LNF piston?

I'm getting slightly interested in this now, maybe piston design changed at some point?