Btw: it seems like the easiest/cheapest way to fix the issue would have been to punch the block out to 30 over.

 

Seems like it would be easier to machine the Block for the pistons. Imagine if he machined a piston and it was out of spec to the block.

But what do any of us know Not like we have a machine shop so we can make up what ever line of bullshit to cover things up....

So whats the story with this story??? Is this a friend of yours, was this posted on another forum, or something to that effect???

 

No way.

This has to be the same person/shop that throws sand into a running engine to port the intake and heads at the same time.

 

Ingenious! I wish I would have thought of that. Actually once the turbo is on my 04 I will crank the boost way up and blow the sand through.... should really clean it up nice!

Friend, no. Local forum for my part of the world dealing with the same retard shops I have dealt with in the past, yes.

It's a Ford 302 destined for a Pinto drag car... or was. The owner is going to tear it down and rebuild it again.... on his dime apparently. The rear main leaks everywhere ( it's only run on the dyno, never in the car yet), it has these custom machined pistons and whatever else wrong he listed...... Here is the original thread:

Bad (engine) news - need help - Performance-Shop.com

I am username Badass69 on there and have my own story. Like how about a supposedly balanced and blue printed big block that..... The pistons dome rub the edge of the heads combustion chamber, the intake valves hit the pistons with no valvetrain installed and the correct thickness head gasket spec'd per the builder.... and the heads weren't torqued. Piston to wall clearance varying by over 0.001" per cylinder and too tight for forged pistons anyhow...... A crank that is scratched and ground in a U shape ( again over a 0.001" variance per journal) and the list goes on. The intake valve seats aren't cut correctly so it's the reason the valve is hanging so low in the seat.... But this was "blueprinted" and ready to run!

If it hadn't sat for over 10 years before I discovered all this ( project was shelved) I would have burnt the shop down of the idiot I paid nearly $10000 to ( he only supplied about the half the parts and didn't machine the block for that... that was another bill).

Now I just do all my own work mostly in a local shop that I am friends with the owner of. And because of that I have seen the handywork of many more local shops that call themselves performance "experts" that are downright scary. We get to see the aftermath when the engine craters and the pissed off owner wants us to tear it down and document what happened. Generally....... they are like my big block inside. Even the last GMPP crate was no better..... and of course GM takes no responsibility for shoddy build quality when the engine is still in fact under warranty....Live and learn.

Much like the tuners up here, "experts" in this part of the world are far too stupid to build an engine correctly...........

 

this is just insane that somebody would turn down a .030 piston. But the sad thing is this isn't the first time I have heard of this. I know some wont believe me but heres were i ran into this. I had my stock LQ9 6.0 block worked over by a local machine shop this was his first ever build on a LS motor. well for some reason he bored the block to 4.020. but he couldn't find a forged low comp boost piston. So I took it upon myself to try and find a piston. well I couldn't find anything online so I started calling around to different piston company to see if I could have a custom one made and at what price. Well I ended up with a sales persons from Diamond and he said making a 4.020 piston wasn't really all that hard to do. he told me he could take a 4.030 piston and have it turned down to a 4.020 bore after he said this I about **** myself. this is no joke thats what he said. I then asked him wouldn't that make the skirt of the piston thinner and he said yes but they have some of the thicker skirts on the market and there would plenty on product to work with. to say the least I got off the phone thinking a lot different about there company or at least who they had as a salesmen.

 

I wouldn't mind the piston manufacturer doing this to a degree, after all, they turn them all down and mill them at the factory in the process; however, I wouldn't trust the local machine shop to do it.

we took a field trip in college to an extruding plant that also made pistons, so I saw it first hand... I just happened to find a video of the process (different plant)
How It's Made Engine Pistons - YouTube

 

Yeah but at the same time if a piston is made to a certain standard. then they take that piston that was a 4.030 and was built to the standard of a 4.030 pistons. then they machine the .005 off all the way around to make it a 4.020 piston wouldn't it now have a thinner skirt all the way around? there for taking away from there standard thickness that they build all other pistons to? I'd rather just have the piston start from a fresh chunk of aluminum and have it made to standards.

 

Piston MFG are not gonna make different spec pistons for different over bore sizes. The only difference is gonna be the final od of the piston. And if removing .005 of an inch (the thickness of 2 hairs) is gonna cause any weakness in the pistons, you have a seriously over machined, light weight piston. The shirts are usually a raw forging on the inside any way and I will bet there is more then a few thou difference from piston to piston anyway.

As far as not trusting a machine shop to shave a small amount off the piston and then hone the block to fit, If you don't trust them to do something as simple as that, then you shouldn't be having them working on your motor to begin with. But this wouldn't work if you have pistons that have already been coated.

The standard practice is just to over bore the cylinder for the piston though. I wouldn't be worrying about leaving meat for a future over bore though.

 

Well said, kb.

I was told by je pistons rep that they use a standard casting for multiple piston applications, and then machine the final specs(piston height, wrist pin od, final piston od, etc) depending on the specific application

 

i highly doubt .010 off would hurt a forged piston

As far as machining them by hand. If you have a 6 jaw chuck and a "last word" type indicator. Its a breeze!