Generation IV Internal Engine - Why is the GM flat crank not used in production models?

Why is it used in the C6R, but not in production engines?

Testing / development maybe?? Just like the C5R had the 427 and was used as the test bed for putting the LS7 into production in the C6. Who knows, the C7 might have a flat crank, smaller cube, higher revving motor as an option.

the other thing is, the C6.R engine has 2 cylinders firing at a time iirc. but to answer your question... COST. the cranks they are using are NOT cheap and are tailor made for the application.

gm has already said the C7 will be 6.2L

the other thing is, the C6.R engine has 2 cylinders firing at a time iirc. but to answer your question... COST. the cranks they are using are NOT cheap and are tailor made for the application.

gm has already said the C7 will be 6.2L


W/ the flat crank, would have to. Yah, cost is probably the reason. Maybe it will show up as an after market option somewhere.

From an OE standpoint a crank is a crank, it doesn't cost any more or less to make a 180* than any other crank...
It prob comes down to things like NVH, or even the tone of the exhaust

simple..gotta leave something left for the years to come

From an OE standpoint a crank is a crank, it doesn't cost any more or less to make a 180* than any other crank...
It prob comes down to things like NVH, or even the tone of the exhaust

You do know a flat crank just cant be simply swapped correct?

There was a thread a while back of an engine dyno flat crank lsx turning like 9000rpms

You do know a flat crank just cant be simply swapped correct?

There was a thread a while back of an engine dyno flat crank lsx turning like 9000rpms


I think you need to match the cam as well and I'm not sure what else. Probably have to do something with moving around injector harnesses and coil packs as well since the valve events will be different.

I remeber there was a lot that was different. And not only the added complication but flat cranks arent as stable either.

I remeber there was a lot that was different. And not only the added complication but flat cranks arent as stable either.


Why on earth would GM use it in the C6R if it wasn't as stable? Also, if it isn't as stable, why can they spin so high?

Why on earth would GM use it in the C6R if it wasn't as stable? Also, if it isn't as stable, why can they spin so high?

I cant explain all those details, look up the thread and there was lots of info about it and why its not stable, yet able to turn stupid rpms.

It's not stable at lower rpm's because of the harmonics. At higher rpm's, the vibrations come into balance naturally.

Remember the 4.3's with the balance shaft?

street car vs race car

always compromises. it's cool at first but drive it every day and you begin to hate your car. that's why i am done with nutty street cars. give me something stock to drive to work and i'll get my kicks at the track.

I've read everywhere that C7 with be a 5.5l over head valve direct injected motor making around 420-430hp

Oh yea and what do you guys mean when saying "flat" crank...I haven't heard of that yet...

heres the thread with the flat crank engine dyno:
http://ls1tech.com/forums/multimedia-exchange/1460148-lingenfelter-flat-crank-ls-engine-dyno.html

lots of info in the thread explaining what it is etc.

I've read everywhere that C7 with be a 5.5l over head valve direct injected motor making around 420-430hp

Been reading to many crappy magazines that are making the assumption that becasue the C6-R program is limited to 5.5L (by rule), that for some reason this is some testament to the street version.

Oh yea and what do you guys mean when saying "flat" crank...I haven't heard of that yet...

Think of it as the current "stock" LS crank looks like a + when viewed from either end where a "flat" crank would look like a - . Stock crank, bearing seats Are located @ 90*. Flat crank, bearing seats are *180.

Oh ok I got you that sounds pretty cool...I love seeing the evolution of GM ohv engines!

Looks like a 4cylinder crank, except there are 2 rods on each journal, and 4 slugs at tdc at the same time and 2 firing at the same time.