It's forged, wonder how that happened. lol that's why i bought the 3core intercooler from ati too add to my setup. what do you think of the Wheeler $1300 shortblock as a replacedment? it is at www.wheelermotorsports.com thanks

 

That is what happens if the top ring gets too hot with too little ring gap. The ring expands with heat and that reduces the ring gap. When there is no gap left the ring will get stuck to the cylinder wall and then the piston starts to move down. This will break the piston above the top ring.

 

yep, you could buy a short block or just rebuild that one with TRW's, arp rod bolts, 1 new rod, proper ring gap, and various other consumables required to rebuilt that motor.

 

yeah, i'm thinking the one on that www.wheeler.com site is the one to get. I could rebuild, but I'll never know if there is other damage without magnaflux, and in the end, after honing atleast all the cylinders and pistons bearings, it'll probably be a better call to get the new motor that i know is good. My question is: Are the "wheeler forged pistons rods and cranks good or not? or should i look else where, I don't want to spend $2000 on a zz4 w/ the wrong pistons to begin with. $1300 is much better. thanks -Justin

 

As I said it is not a piston fault. It is a ring-gap or tuning fault.
Read this and compare that piston to yours:
http://www.kb-silvolite.com/speclear.htm

I don't know anything about the wheeler brand.

 

Interesting.
Thou, I don't follow their logic.
It says that the piston reflects heat back into the combustion process. To me, that means the piston would run cooler, not hotter. If in fact the piston runs cooler, and breaks that would mean it is softer then the other style.

If it needs a larger gap, then that contradicts what they're claiming.

 

What they are saying is that the kb-silvolite pistons are designed for higher combustion temeratures. This will increase the temperature of the top ring and that is why it needs more ring gap.

My point was only to show that this is the type of damage you get when the top ring gets too hot and the ring ends butt and lock tight in the cylinder.

 

thats the way my KB's looked after ring butting, I was able to look at the other gaps post mortem and found clearances in the .016-.018 were aroung .010 too tight fr my "application"

 

anybody have input on the $1300 shortblock @ www.wheeler.com ? thanks

 

well that wheeler link dont work

 

duh, try this: www.wheelermotorsports.com thanks!

 

or even pop a few hund and get the 383

 

but what do you think about the motor, especially their "Wheeler" brand components? any experiences, thanks

 

Do like B4Ctom1 did and do a post mortem of the ring gap on each piston in the corresponding bore. If its too tight, then you have found the culprit. Also look at where the ring butts together for evidence of contacting each other. I'll bet that you'll find the ring gap the tightest in the damaged piston cylinder.

I kinda see your point now, you don't trust the pistons.

It's not too hard to measure the rig gap. A piston to push down and "square up" the ring and feeler gauges.

The block you that you get from Wheeler could have the same problem. You have found the problem, get the block to the machine shop and see if just a honing will clean up the cylinder. If so, then get a single piston and CHECK CHECK CHECK the ring gap.

 

That site looks pretty good. I would upgrade to a forged crank though.

Call them and find out what style block that is. Most of the sites I have been to use 2 peice rear main seals and non roller blocks. If you goto www.larrysperformance.com, they sell ready to go blocks for ~$400. When I called them, a 1 peice RPC, roller block was an additional $200.. I was a little pissed at that, especially since there was no mention of it on the site.

 

okay well, i'm still not sure that if i repair the piston, that everything else will be ok. How do i know there isn't more damage. I would like to save the money, but i don't want to end up pulling it back out soon.
Does anybody have any other suggestions or good deals on shortblocks?
Also if the ring gap is too tight, then won't I have to do all the pistons,.. besides i'm sure the bearings got damaged. Also, is it possible that this is just from detonation that cracked the edge of the piston off, and not from "binding" the ring on the cyl wall? what else could be damaged.

 

Pic of piston damage to a hypereutectic. There is detonation damage on the piston with no ring land damage.

 

Pic of the Hypereutectic (HE) piston with ring land damage. These pics are from the DIY-EFI.org site. The owner of the pistons was complaining about how crapping HE pistons were. But there is obvious damage of detonation and too tight ring gap.

Justin 87 GTA., measure the ring gap of each bore with the respective ring and post those numbers on this board. From there we can make a judgment based on factual numbers.

I'm impressed on what little damage was done to the top of your piston.

 

PLEASE NOTE THAT EVERY PISTON TYPE HAS IT'S OWN RECOMMENDED RING GAP!!!! FOLLOW RECOMMENDATIONS!!!

KB Hypereutectics, for instance require a gap of .025 or so on a street N/A motor. If you're gonna throw boost or nitrous at it they recommend a whopping .033"!! This sounds like a HUGE gap. But it works fantastic. That's exactly what I gapped them at in my current 383. I was expecting a lot of blow-by from the large top gap but there is almost none. Imagine that: follow directions and it works great.

Lot of engine builders just assume they can jsut use the old .004-.005" per inch of bore equation and come up with the right answer for every case. WRONG! READ DIRECTIONS THAT COME WITH THE PISTONS!!

 

amazing...instructions actually work lol

i was gonna buy the wheeler 406 shortblock, but i got a helluva deal on a 475 horse LT1..so its "only" a 350 for me

 

well thanks for the ideas and info. Still, does anyone know how these "wheeler" internals are, and if you can cutomize the pisons and gap and compression.

 

definitely Damon, KB has probably the most intense instructions offered with any piston I have ever purchased. From cast to $150 ea custom KB has them all beat in the instructions department and with good reason. Close study of KB gap instructions on motor after motor has me gapping even non KB motors that way just to play it safe.

 

Tom, yeah, me too! I'm getting so little blow-by with my .033" top gap in my current blown 383 I see no reason not to err on the side of safety, even in N/A applications.

I screwed together another one (using KB Hypercowabungas) that was built for N/A but went with the larger .033 gap "just in case" I wanted to tickle it with some nitrous a little later.

Probably overkill if you're talking about true cheap-o "cast" pistons. But it's one of those areas where I always thought better to tight than loose..... and have since switched my opinion.

 

heh. im running .035-.038 on my TRW's.

now its a N/A 355 TPI motor. can you imagine what those pistons must be thinking?

its okay... i have a 300 shot planned...

 

I think my 412 (4.185") has like .028-.032 on the TRWs for what? hell if I know, its one of those "just in case" kind of things.

 

I wanna know more about this LT1. Got any parts details?!

 

well, i feel better now, i just gapped them all at .024 for the top ring and .026 for the bottom ring,.. as per the instructions. However, one bottome ring i overfiled to .32 and 2 other bottom rings to .040+. I thought that was way too big, but i guess it's okay. Should i increase all the other ring end gaps or not. I am planning on just leaving it, but those 3 cylinders will have top ring gaps of .024 and bottoms ring end gaps of abot .040. that's ok right? thanks

 

If you want to do it right I would get another set of rings.

.040+ gap on any ring in my opinion is wacky. not even the KB pistons want that much gap... and yours are speed pro (sealed power) which i beleive most recommend in the .018-.020 gap for N/A... which puts you in the .025MAX area for boost.

correct me if im wrong.

 

okay, just wanted to know if it was bad,.. or just not great. thanks for your input

 

I got KB Hypers with a big fat .034 gap on the top ring.

Its all good in the hood so far.

 

well thnak guys, i got the new rings,.. now i need to pic a cam, lifters and springs. also rr's/ any ideas? XE cam? thanks