Mahle pistons?

[racin460]

Why do a lot of people say to replace your pistons with Mahle, because there the manufacture of the original piston?

If the original pistons crack across the top at the exhaust valve relief?(mine have 3 out of 8 cracked on an engine with around 80,000 miles on it) now that was a water company service truck so I know it ran more in sitting time than miles but, there still cracked....

Are the original pistons CAST or FORGED?

Are the new Mahle piston CAST or FORGED?

I won't rebuild a sbc with cast pistons, so I shore don't want to put a cast piston in something with twice the compression.
I've looked every were for the info on the Mahle #144171HAWR and can't find any thing that say cast or forged.
(That # is for the non turbo wrist pin, 0.010 lower compression height, coated tops, w/rings & wrist pin)

 

[RLDSL]

that is not the norm. You need to step back and try to figure out what happened in that engine to cause that sort or damage. Ether use? Broken glow plug tips run through ? really bad timing? heavily slobbering injectors? I'm sure I've left out a half dozen other possibilities for that sort of end result on a diesel, but , I'm tired

 

[Wyreth]

Also, call Mahle and ask them point blank.

Ish what I would do.

 

[idiabuse]

Hyperutectic pistonas

Javier

 

[typ4]

Mahle pistons are forged.

 

[hesutton]

Those are not valve reliefs. Those are the combustion cups.

Heath

 

[icanfixall]

Mahle pistons are forged pistons as Russ has posted. Robert hit the nail on the head. Cracks in pistons are there for a reason... finding it may not be possible because we normally are not the first owner of these engines. Many reasons for cracks. As for the top of the piston being weak... Not true. The thinnest area of the piston top is 560 to 580 thousands thick. Thats well over 1/2 inch thick. Now lets talk about those "valve reliefs" in the tops... Those are Ricardo reliefs.... Not valves reliefs in the piston tops. They have nothing to do with the valves. If someone can post a pic of a valve contacting the piston top you can clearly see these are nowhere near a valve relief. We also have a flame trench made into the piston top so the flame exiting the precup does not burn the piston. Remember the piston is only around 42 thousands from the head at tdc. And all the volume of the bore & stroke is compressed into the precup. When combustion happens it has to get out of there someway.. The Ricardo cups capture that and spread the power across the piston.

 

[riotwarrior]

.....If someone can post a pic of a valve contacting the piston top you can clearly see these are nowhere near a valve relief. ......

Gary,

Ask n YE shall receive

Here is a piston with a lil modification I like to refer to as Smack n Bash....

You must be registered for see images attach

You can clearly see the valve contact on the piston...and it aint pretty!

Al

 

[RLDSL]

AH. a lil luv tap there

 

[Dsl_Dog_Treat]

Gary,

Ask n YE shall receive

Here is a piston with a lil modification I like to refer to as Smack n Bash....

You must be registered for see images attach

You can clearly see the valve contact on the piston...and it aint pretty!

Al

That's too "Pretty" Al.

Here's one that's a lil more gruesome.

You must be registered for see images attach

 

[jaluhn83]

Russ,

Are you sure they're forged?

Forged vs cast may not be as big of an issue as you think. Likewise hyper-eutetic vs non.....

Most diesel pistons are cast because they use a steel top ring groove insert due to the higher pressures on the diesel. You can't do an insert like that on a forged piston, so forged pistons run the ring directly on the aluminum. You can annodize the Al but it's not going to be as hard or tough as steel.

Forging gets you greater material strength per weight, but for a big heavy low speed piston like this it's pretty irrelevant. More of an issue on a high speed engine where you're trying to make super high rpms.

Likewise, hypereutetic is not an end all be all. The main reason that alloy is used is that it has lower thermal expansion allowing closer clearances and helping with emissions. It does make the alloy somewhat stronger, but at the expense of being more brittle.

Don't fall into the trap of thinking that what works for a sbc racing engine is necessarily the best for a turbo diesel.....

Under Pressure
The pistons in a diesel engine must also withstand significantly higher compression pressures and operating temperatures than those in a gasoline engine. Because of this, the top piston ring runs hot. To reduce top ring pound out, most stock diesel pistons have a steel or iron insert for the top ring groove. This greatly improves the durability of the piston, and also allows the use of a keystone-shaped top ring to minimize ring sticking.

Because the pistons need a top ring groove insert for durability, the pistons must be cast rather than forged. Most use an alloy that contains 11 to 13 percent silicon so the pistons will have some ductility. To date, hypereutectic alloys with higher silicon levels have not been used for diesel pistons.

Source:
http://www.enginebuildermag.com/Article/1788/diesel_pistons.aspx

 

[icanfixall]

Ouch moma.... Ron.. That hurts looking at that.... Ewww... And thanks Al for bringing that up so fast... Both of you clearly show what I was posting about. This is one area where touching is never a good thing....

 

[Dsl_Dog_Treat]

Gary that's the one I was telling you about that a prior shop chose to run. Prolly never replaced the guide, it broke off and allowed the valve to wobble around in the head and nearly knocked the valve seat back out of the head. It's no wonder it popped a 160 psi on a comp test.

 

[typ4]

yes mahle is still forged, just left my parts guys place, he says unless clevite who now owns mahle changed them. We pulled one out and they are definately forged.

I personally would never run a hypereutectic in a diesel. too brittle

 

[racin460]

WOW!!!!! You guys can really make an unsure situation very clear thank you to all that posted