Thanks for the info.

 

[QUOTE=SS RRR;19543331]Who was it?

Brad96ws6 was the guy I bought it from. Here was the ad for it.

https://ls1tech.com/forums/parts-classifieds/1820578-lt1-383-stroker-sold.html

 

HI ALL, the "BAD" tech's here.
OK sure, throw "safety/quality" OUT THE WINDOW.

MY concern is complete engine inspection.
MY observation is based on the first picture stating a damaged cylinder bore.
There is a chance of a reflection in the picture, though it looks like a gouge.

The piston is measured under the Oil Ring, NOT the Tang Ends, perpendicular to the PIN.
The piston Ring Land is ALWAYS much less in diameter than the the OIL Ring Measurement.
This is due to the "heat" at the Top Ring area.

The newest pictures of the pistons look much better, though the Valve Notch looks like one from a cast piston.
My first "guess" was a picture of a cast piston.

There is ONE method not yet stated, A "thin wall" sleeve in the bad cylinder.
The first step is to Hone the damaged cylinder, find the piston part # on the bottom.
This could be a JE "shelf" piston, if so buy one, due a thin wall sleeve, keep the other pistons if in perfect shape.

I would like the Head Gasket Part # ?

NOW for my "BAD" tech :
I assemble engines with MY ECU-882 that run for 25K Hours continuous @ 18:1 AFR. (lean)
When the engine goes "lean" combustion temperatures DROP.
I learned this in HS Chemistry class.

An incorrect Spark Instant is what causes damage of this sort.

Lance

 

Lance, a lean engine runs hotter. What AFR burns hotter, 9:1 or 15:1 or 20:1? When we say lean we are talking 14.7:1 (stoich) or richer. Most of us run 11-13:1 AFR at WOT. 11:1 runs cooler than 13:1. 14.7:1 will burn a hole right through the piston.

It's possible to run 18:1 AFR, but there are other factors involved that would make it work reliably. Spark timing being one of them.

Sure you can blame spark timing being to far advanced leading to detonation or pre-ignition. But if spark timing is at or below what is normally run, then AFR is to blame. AFR that is leaner than it should be (not leaner than stoich).

Out of curiosity, what motor do you have running at 18:1 for 25k hours? Power output? Rpm? Sounds like a generator type set up or a pump? Constant or variable RPM and load?

 

Yeeesh... only 11 posts. Did he supply a dyno sheet and time slips to support his "7xxhp/low 10's all day.." claim?

 

He did provide a dyno sheet and receipts for the shop doing the work. I also talked to the shop who built it so I know it was built by a shop. Finish Line Performance out of Naperville IL did the work on his car.

 

Sounds like he may have sold you a beat motor

 

in that HP range and running 18 lbs of boost....that is tree top level for a LT1 with power adder. Possible the motor got "hurt" during dyno time or within the 2k mi the motor supposedly has on it from PO....and I suspect some of that 2k miles were 1/4 mi at a time

Interesting PO spent $6500 on a motor and decided to sell it with just supposedly little use/milage

If tune is not DEAD NUTS on for a 18 lb boost motor and every part working right (fuel system) serious engine damage can...and obviuosly does occur

I suspect if the OP discovered the coolant spewing on 1st start up the PO knew something was up....or should have.

 

My last engine was a boosted 383 with SRP pistons.it was a great motor.lasted for years and survives all kinds of stupid mistakes on my part.
The last mishap that did it in was a meth system failure and a few pistons had those same type of cracks from going lean but more importantly the massive heat as i was notintercooled. Munched a ring land as well and crushed the top ring.

 

Yeah it all makes sense now looking back at the purchase. He told me he was selling it because his trans blew at the track and caused him to spin out and hit the wall. I'm guessing the motor blew a gasket causing the coolant to come out of the exhaust which hit the tires and caused him to hit the wall..

 

It doesnt take multiple pulls on a dyno or several runs down a track to do damage due to incorrect timing or A/F, just one time will do it.....

 

Its not uncommon for the top land to be shrunk up to .045 from bore size. Depending on the material and who made those pistons it looks normal.

 

First I've heard of that. I always thought piston diameter was uniform from top to bottom.

 

It's not. That's why we measure clearance at the skirt. But I've never seen a gap that big.

 

Amazing someone can eyeball 0.003" from a single picture of a single bore.

 

Did some reading up and see that it varies from piston to piston. The things you learn! And yes, that's why I agree on the gap issue since the engines I've cracked open have never had that big of a gap on the non-thrust side of the bore.

 

Lmao!

 

That's more than .003", but point taken.

However, ever notice how you can tell if someone is looking at you or not from across the room? 20 feet away and you can tell if their eyeball is looking at you or something next to you? How much accuracy do you think that is? Can you tell the difference of a 10 or 11mm socket sitting next to each other from across the garage? That's 1mm difference from 20 feet away. The human eye ball is more accurate than most people think of it. It's like eye balling a picture on the wall to make it level. Try that then check it with a level, most people will be surprise with how close it is, if it's off level at all....

 

I'm just commenting that someone can decide the exact size of replacement piston required from a single picture. 0.003" total, which means 0.0015" per side. 1mm is not that small it's about 0.040" which means that someone is able eyeball something smaller than 1/20 that size per side and of course this is before any machine work.

all of this is also being done without even accounting for parallax error due to the angle of the photo.

 

you maybe onto something. took a pic of a stock block i have with the stock pistons. cylinders have only ever been rehoned.