Gen 5 small block piston!

[c4c5specialist]

I got my hands on one. This design is sick as hell and seeing it in my hands, I can truly understand all the fine points to this piston design!

What do you all think?

Allthebest, Paul

PS, yes I am proud to be the FIRST to POST in technical!

 

[catbert]

That is sick. How long did it take to come up with that crown swirl pattern? Remember flat top pistons?

 

[Toms007]

Holy crap! There's some engineering that went on there.

 

[Hib Halverson]

The design of the piston top is to compliment DGI when it injects the fuel. The piston top and the chamber cause a lot of swirl, the fuel is injected into that swirl then the plug fires.

LS6 and LS7 pistons were Mahles. The piston supplier was changed for Gen V from Mahle to Federal-Mogul.

That piston is almost too pretty to be in an engine.

 

[Tuna]

I think I need one for my display case!

 

[c4c5specialist]

Federal Mogul made the LS3 piston as well as the GEN 5 piston.

Piston on the bottom is an LS3, piston on the top is Gen 5 small block.


FM cast into the piston is clearly visible in both skirt undersides.

Allthebest, Paul

 

[ltmax]

Great CAD design for the top in use with the direct injection. What kind of scares me is the minimal skirt height. That's got to be a lot of stress on such a short height to resist rocking motion, 'specially under combustion. You can see the side coating scraped off the lower LS3 piston in your picture there. I know they had a problem with it ~10 years ago and have improved it but this CAD-design metal removal is getting scary. I imagine this design would increase the importance of always keeping the best oil at the right levels. Certainly worth it!

 

[bill81vette]

Great pics Paul!!!!
Thanks!!!!

Sent from my DROID RAZR using Tapatalk 2

 

[Mac]

Some of us old school guys look at this kind of technology with suspicion... is it witchcraft to produce so much power AND decent gas mileage? :ugh

Thanks, Paul. Very cool, indeed!!

-Mac

 

[motorman]

Some of us old school guys look at this kind of technology with suspicion... is it witchcraft to produce so much power AND decent gas mileage? :ugh

Thanks, Paul. Very cool, indeed!!

-Mac

similar to diesel piston design which are DI except for the valve relief. THANK GOD for computer controlled machine tools

 

[Dad]

That is not an LT1 piston, may be one of the prototypes but not a production piston.

 

[Hib Halverson]

So we all have a better understanding of LT1 parts, please, tell us the difference between a prototype LT1 piston and a production LT1 piston.

 

[Dad]

Take a look at the 2014 C7 pictures posted by Bob a few months back, (about page 5 fo 2014 C7) they clearly show the production piston. It has only two cuts that do not require CNC machines to make but will most likely have dedicated maching pod to make the pistons in the required volumn. A prototype such as one shown at the beginning of this thread has markings that will be used to track the piston after test. Not sure what is used to mark them now, we used laser/acid etch and/or mechanically etch on all parts many places so they could be identified in distructive testing also in court/patent disputes.

I would still like to know why they changed the valve locations in the heads, got any ideas?

 

[c4c5specialist]

HI there,

Actually, yes, that is a production piston, I order it through normal parts chain within GM dealerships. I also ordered a cylinder head at the same time, which I have.

Allthebest, paul

 

[Dad]

Believe what you want but that is not a production piston.




Since these are through the assembly process my guess would be that they are production pistons. Last picture is a LT1 and the LS3.

 

[c4c5specialist]

HI there,

Those photos are GM media and are computer generated and touched up, sorry.

And you can prove it to yourself instead of taking my word for it, so you can see for yourself. Buy the same piston I did from GM.

Left piston part number: 12656875 which is the one I bought at $56.78

Right piston part number: 12656874 $56.74

Allthebest, Paul

 

[Dad]

That would only prove that I got a part from the same batch as you did. Those parts can be and often are the remaining prototypes used to prove a viable functioning part. They are at times over run on purpose to cover parts requirements after a new model is released. Not long but just enough to cover crisis situations that do occur before production requirements present a supply that allows for spares. I've been through many programs from concept through obsolescence and it has always followed that format. We seldom if ever made one part to test a new design and we never put it out to the market until it had many of them tested for durability. That said I've never had to touch up a photograph to prove what my parts looked like, but if I did in this case I would think the entire top would have been retouched. Why leave the 2 milled pockets as machined and not the fancy circular interpolation on the top with them? I think they are making them today with a near shape top with the 2 machined pockets only because their present method doesn't allow the accuracy they want, so there are some simple clean up cuts made to finish the part. I no longer have anyone working at the engine plant to see what is actually being used and doubt I would even ask them to jeopardize their job to find out. Always enjoyed going into the Flint plant when they were building the Corvette engines but those days are over so I'll have to rely on someone else setting this issue straight.

 

[c4c5specialist]

That said I've never had to touch up a photograph to prove what my parts looked like, but if I did in this case I would think the entire top would have been retouched. Why leave the 2 milled pockets as machined and not the fancy circular interpolation on the top with them? I think they are making them today with a near shape top with the 2 machined pockets only because their present method doesn't allow the accuracy they want, so there are some simple clean up cuts made to finish the part. QUOTE]

Really? Prototypes are exactly that and are NEVER EVER installed on factory engines for release to the public, you should know that. This isnt about YOU or what you would do, this isnt about your parts, whatever they are. These are factory PRODUCTION parts vs GM media posting that are not.

I would think that you would understand that given your in depth knowledge on the subject.

Allthebest, Paul

 

[Dad]

Never say never, this may be what woud be preproduction parts from the last run of prototypes. Keeping track of parts at some point draw a production number to get the manuals moving. Same with parts as they reach the production stage they may or may not be completly developed. What you are telling me is if you receive a part from GM it will always be the same and we all know that to be untrue.

Many times durning a parts life there were changes and not always would it be enough to change its number. We built balancers by the million and as you know they had failures and those failures caused manufacturing changes that did not always change the part number. That's a manufacturing fact and I don't see anything in todays parts that is any different.

I'm not picking on GM they were about in the middle of the pack for their running changes, and that pack inclued Ford, Chrysler, Honda, MB, and later Boeing and Lockeed Martin. Today manufacturing is changing as it needs to but some parts of it do not, people. Some will shave a little off here and there to keep things moving.

A quick guestion for you, have you ever had the head off a GM direct injected engine? If so what did the chamber, piston top look like, carbon wise and finish?

 

[Hib Halverson]

Hey "Dad"...ad enough already!

First, the images you posted are GM Powertrain PR images which are shot way before replacement parts, like the piston Paul bought at a dealer parts counter, get into the GM parts pipeline, and likely before any production engines are built.

Secondly, you're making a dumb argument with, "c4c5 Specialist" one of the top Corvette technical authorities on the Internet. It's highly unlikely your resume for Corvette expertise can match his.

The piston the OP on this thread was discussing is a production unit. The piston in the imagery Rob posted a number of months ago may not have been a production part and is, also, likely, to have been run though a lot of photoshop.