GOSFAST

The photos below show why we recommend avoiding "cast" pistons in ANY performance oriented builds, you just never know when you need the forged pieces.

It's also another reason why we avoid "crate" motors, usually that's where the pieces end up??

Thanks, Gary in N.Y.

P.S. Not sure a forged piece would not have failed either, but I doubt it would be like these in the end??

TimAT

M R Broken!

427Hotrod

If I'm building something to "lean on".....or especially if building for someone else....it's going to have forged pistons.

I'd trust some 1969 cast pistons better than many of the replacement cast and many Hypereutectics out there today.

The cost difference just isn't that much and unless you've got full engine management to control detonation like the OEM's...and using true OEM quality pistons, you're gambling. The hypereutectics used on the high end OEM engines is a lot different than what is sold on the net in general.

JIM

cv67

x2
OEMs with good spark/air fuel management allows mfr to get away with using them....personally Id take the lousiest forged for 100 or so more
When they break its like a bomb went off in the motor usually takes out everything sometimes the carb, too.

Buccaneer

X3
It's just NOT worth it to save a few dollars on a build that you just spent thousands of dollars on. To quote someone when it goes, it goes... "BIG LEAGUE".

Metalhead140

Got to ask though... Any ideas on the cause? Ring gaps too tight?

CanadaGrant

Look at the deep blueing and heat scorch on the top of those rods. Something else at work there besides cast or forged pistons....

TCracingCA

My joint Porsche World to my Corvette addiction, they love cast pistons for tighter piston to cylinder clearances, but they coat them!

Buccaneer

It looks more like detonation due to top ring area pieces missing, but to verify that you would have to look at the lower rod bearings to see if they were wore badly and the top bearing OK. If it was detonating, the lower bearings would probably be down to copper or copper showing IMO. Whatever it was, it was really bad.

bfit

Well those conrods have been HOT, that tells me that something is very wrong other than the cast pistons, that blue colour tells a story.
Having said that, would not bother with cast pistons even for a daily driver .
Build it right and it will stay together longer.

cv67

doent porsche use mahl?

L88Plus

I haven't come across any cheap cast pistons that were set up for floating rods - that would explain the heat on the pin end of the rod.

In my limited engine building world, "cast" and "performance" aren't to be used in the same sentence or build.

bashcraft

Yeah, it tells you how the wristpins were inserted into the rods.

bashcraft

This was caused by severe detonation. A forged piston may have lasted a little longer, but the final outcome would've been similar.

Pop Chevy

Cast or hypereutetics pistons do not tolerate detonation well , nor do they like high rpms or nitrous.

GOSFAST

Just about everyone is correct here for the most part.

It was detonation, but it wasn't a "lingering" issue, it was spontaneous, happened instantly. Matter of a few "seconds".

Hard to believe but there is NOTHING visible when viewing the pistons directly from the top, not even the slight burned section above the one piston in the picture. It is evident from the side but not from the top.

The above comments about the "blue" rods is also correct, it is from the "rod-heater" during piston installation. This is a non-issue generally speaking.

The other shot below here is the brgs, there is nothing "outstandingly noticeable" about the surfaces. You would normally see some deterioration of the upper brg shells under these circumstances. With this not apparent we know it was a "very quick" event.

Thanks, Gary in N.Y.

P.S. Like I stated above, a forged piston would have helped, but NOT stopped it, would most likely have a lesser extent of damage??

REELAV8R

The piston top design is poor for high compression/performance use.

If you are going to use a dish piston a D-Dish is better for detonation avoidance. It has an actual quench/squish pad.

Two stroke racing motorcycles from the OEM's have/had cast pistons and turned 12000 RPM with as high as 14:1 compression with no failures such as these had. No doubt that forged pistons are much hardier, but I wouldn't blame this failure on the fact that they were cast vs forged.
The skirts would fracture if the cylinder was allowed to get too worn before overhaul. Piston slap caused that kind of failure in the two stroke bikes with cast pistons. Excessive detonation would simply "hole" the piston.

TCracingCA

In the modern, Mahle has all of the same modern pistons and materials as everyone now and they offer V-8, Diesel Truck pistons and you name it. The old Race Units like that Vasek Polak used to sell where cast, but coated. I am not a piston expert, but the air cooled world is a bit different. My favorite Manufacturer is Ross, and I have all real Forged units, no hyper???whatever ones. With the Ring technology, the seal and fit to the cylinder walls with like moly rings and stuff, I just choose to have the stoutest units, money can buy! My Brother is the modern Porsche guy and is an encyclopedia on everything Porsche. He was talking about original build normally aspirated racing engines recently, and half one going in one ear and out the other. But I would say whatever a Company like Porsche or Ferrari or others are choosing and doing, is probably the best technology, but not necessarily in the average humans price range.

SH-60B

All those LS style truck motors have hypers, and they boost those to 1000hp

TCracingCA

But aren't they coating those to get to those levels????