Cast Vs Forged Pistions

[K1SSRSS]

Good afternoon, I have a question that has been bugging me ever since I have been researching building a Duramax.

Why does it seem that everybody is running cast pistons on their engine builds?

Coming from the gas burner side of things, I have built well over 100 performance oriented motors and have never considered using cast pistons, the only time I would not use forged pistons would be on quick revving circle track cars to keep down rotational weight. As far as forced induction motors go, there is no way I would consider anything other than a forged piston.

I am sure I am missing something, but with all the talk we hear of with high EGTs melting pistons, I would think forged pistons especially on a high compression force fed diesel would be a no brainer.

Not trying to bash anybody or anything like that for using cast pistons as they seem to work for the most part, I would just like some enlightenment as to why since I have plans to dabble in a couple of diesel builds here in the near future.

Thanks all.

 

[blue09dmaxx]

Good afternoon, I have a question that has been bugging me ever since I have been researching building a Duramax.

Why does it seem that everybody is running cast pistons on their engine builds?

Coming from the gas burner side of things, I have built well over 100 performance oriented motors and have never considered using cast pistons, the only time I would not use forged pistons would be on quick revving circle track cars to keep down rotational weight. As far as forced induction motors go, there is no way I would consider anything other than a forged piston.

I am sure I am missing something, but with all the talk we hear of with high EGTs melting pistons, I would think forged pistons especially on a high compression force fed diesel would be a no brainer.

Not trying to bash anybody or anything like that for using cast pistons as they seem to work for the most part, I would just like some enlightenment as to why since I have plans to dabble in a couple of diesel builds here in the near future.

Thanks all.

They need to be reringed every so often where as cast doesn't if it's a toy/no miles engine go forged

 

[mike diesel]

There is no need to run forged for most guys. Standard sets of cast pistons can do 1000 horse just fine. Even stock lb7/lly mahle pistons can do 800+ no problem. A set of fingers oval bowl cast pistons have been pushed to 1700 horsepower with no issues.

Alot of guys still use their built engine truck on a daily basis. Forged pistons are not an option for them.

 

[moparkxracer]

I can't wait to see how mine do. Hope they last.

 

[sickdiesel]

I put forged in mine because it is only a weekend toy/race truck. ive put maybe 1700 miles on it in the past 2 years

 

[bml2200]

I cracked a Mahle delipped cast piston around 900hp and went with forged for the rebuild.

 

[K1SSRSS]

Thanks guys, however I am now trying to figure out the mechanical reasoning behind the decreased life running forged.

What I'm starting to guess is it must be the larger ring gap necessary to run forged pistons lends itself to excessive blow-by with the additional compression and boost used in diesel applications.

But heck, I dream of being around the 1000hp mark some day so if the cast pistons hold up and seem to correlate with longer engine life, that is the way I will go.

I am still just slightly baffled, since I have never noticed much of a difference in gasoline engine lifespan between running forged, hyperteutic or cast pistons.

 

[sickdiesel]

Thanks guys, however I am now trying to figure out the mechanical reasoning behind the decreased life running forged.

What I'm starting to guess is it must be the larger ring gap necessary to run forged pistons lends itself to excessive blow-by with the additional compression and boost used in diesel applications.

But heck, I dream of being around the 1000hp mark some day so if the cast pistons hold up and seem to correlate with longer engine life, that is the way I will go.

I am still just slightly baffled, since I have never noticed much of a difference in gasoline engine lifespan between running forged, hyperteutic or cast pistons.

forged just dont have the hardened steel ringland inserts like the cast pistons do. The rings basically just beat away the ringlands over time. especially in cold weather and if the truck is cold started often.

 

[delong_1]

forged just dont have the hardened steel ringland inserts like the cast pistons do. The rings basically just beat away the ringlands over time. especially in cold weather and if the truck is cold started often.

that or you have to run a soft top ring to save the ring land

 

[K1SSRSS]

That makes sense now, I never realized the diesel pistons had steel inserts on the ring lands of the cast pistons. :thumb:

 

[56taskforce]

In the gas burner world cast pistons also have a steel support cast in to them it doesn't support the rings but it keeps the piston at a more consistent size through heat cycles.

 

[56taskforce]

Forged pistons require more clearance for expansion and contraction during heat cycles.
The extra clearance makes them sloppy when cold. It is not recommended to run forged piston's in a gas street motor either.
I am new to the diesel performance world as well and was not aware that cast diesel pistons had steel ring lands. What I want to know is anyone building hyper eutectic pistons for diesels?

 

[ikeG]

I cracked a Mahle delipped cast piston around 900hp and went with forged for the rebuild.

Was it a Mahle stock replacement or a Mahle Motorsports piston??

 

[Fingers]

Cast pistons have the oil gallery cast into the piston to help keep the fire ring temps in check. Forged do no. Longevity wise, this is an advantage especially if you tow with your truck on the street.