Looking for a picture and the difference of the LB7 and the later style pistons.

[malibu795]

Are the 300k pistons cast or forged? Thanks

Mine are race cast with 17.5:1CR
They can be had with either moly rings or stainless rings.. pros and cons to both.
Take what I say with a grain of salt.. when I reference something it's generally on 50-100k mile intervals..
And the truck dragged a 25,000-29,000lb trailer for 500-650 miles a day 5-6 days a week at a dynod 400/800 tune for 4 years roughly.

 

[ikeG]

I question the efficacy of delipping these pistons, personally, when the correct injector and timing is being used. I'd much rather have more complete combustion with the eddy created by the lip utilizing the correct flow and spray angle of the injector, than building the engine knowing I'm reducing the combustion efficiency even a few percent.

Turns out the Wagler "delipped" pistons have .010 taken off the top and are not delipped. This is their standard off the shelf piston but you can order them any way you want. I ended up having 2 lml short blocks here at 1 time to do. One of them was totally stock, used the 224-3935 set in it. The other was a callies crank, Wagler piston, etc mild upgrade engine. So I measured both bowls and then asked wagler what was up.

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[Chevy1925]

Turns out the Wagler "delipped" pistons have .010 taken off the top and are not delipped. This is their standard off the shelf piston but you can order them any way you want. I ended up having 2 lml short blocks here at 1 time to do. One of them was totally stock, used the 224-3935 set in it. The other was a callies crank, Wagler piston, etc mild upgrade engine. So I measured both bowls and then asked wagler what was up.

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why even take .010 off the top? in prep for a decked block?

 

[Bdsankey]

Turns out the Wagler "delipped" pistons have .010 taken off the top and are not delipped. This is their standard off the shelf piston but you can order them any way you want. I ended up having 2 lml short blocks here at 1 time to do. One of them was totally stock, used the 224-3935 set in it. The other was a callies crank, Wagler piston, etc mild upgrade engine. So I measured both bowls and then asked wagler what was up.

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This kind of goes back to when Wagler first released the street fighter package and advertised them with a "race" piston that was delipped and had a worked over bowl when in actuality it was this off the shelf piston that had CH removed.

why even take .010 off the top? in prep for a decked block?

I'm wondering if it's to mimic a race cast piston as they are 0.010" removed off CH direct from Mahle? This is speculation/guessing on my end so I hope nobody takes it as gospel.

 

[Gentrysgarage]

Thanks for the replies I have been busy with researching the ECM end of things and it is getting interesting. I will be going with the race cast LML pistons.

Mine are race cast with 17.5:1CR
They can be had with either moly rings or stainless rings.. pros and cons to both.
Take what I say with a grain of salt.. when I reference something it's generally on 50-100k mile intervals..
And the truck dragged a 25,000-29,000lb trailer for 500-650 miles a day 5-6 days a week at a dynod 400/800 tune for 4 years roughly.

Which ring material did you use in the 300k motor? Thanks

 

[JoshH]

I don't believe they make a race cast specifically for the LML. They make stock replacements that are specific to each generation (LB7/LLY, LBZ/LMM, and LML) but can be used interchangeabley on different generations depending on the parts being used in your build, or they make the race cast which fits all generations.

 

[malibu795]

Thanks for the replies I have been busy with researching the ECM end of things and it is getting interesting. I will be going with the race cast LML pistons.

Which ring material did you use in the 300k motor? Thanks

I never had a complete engine last 300k in my line of work that I was using it in. That's rough cumulative total.. think those pistons have been in 4? Blocks.. I'd have a block die on me for X reason.. I'd get a seasoned block drop of a fleece, with the rotating assembly, have everything checked. then block bored to spec for said pistons with new rings/bearings

The longest on engine lasted was around 230-250k in which it cracked the main web, DS on #4 main web. which engine started to lose oil pressure, and I pulled the engine. That one had SS ring pack.. iirc block wore faster with SS rings.... With Moly rings wore out faster than the block.
The cylinder wall wore ~1/2 the speed with moly rings than what the SS rings did.
Per service manual piston to wall clearance limit is .010".. mahle race cast is/was .0015-.002". I set my new blocks between .002-003"..

Keep in mind my engines ran at 50-75% duty cycle on average at a ~400rwhp rating...

Avg daily driver weekend hauler might see 25-30% avg duty cycle.. which the point could easily be made lighter duty cycle substantially longer mileage life

 

[Gentrysgarage]

I don't believe they make a race cast specifically for the LML. They make stock replacements that are specific to each generation (LB7/LLY, LBZ/LMM, and LML) but can be used interchangeabley on different generations depending on the parts being used in your build, or they make the race cast which fits all generations.

I am confused, I thought those where the same as what Jeremy Wagler is using and they had oval bowls. Sooo is there a race cast oval bowl and can someone post a part number?

I never had a complete engine last 300k in my line of work that I was using it in. That's rough cumulative total.. think those pistons have been in 4? Blocks.. I'd have a block die on me for X reason.. I'd get a seasoned block drop of a fleece, with the rotating assembly, have everything checked. then block bored to spec for said pistons with new rings/bearings

The longest on engine lasted was around 230-250k in which it cracked the main web, DS on #4 main web. which engine started to lose oil pressure, and I pulled the engine. That one had SS ring pack.. iirc block wore faster with SS rings.... With Moly rings wore out faster than the block.
The cylinder wall wore ~1/2 the speed with moly rings than what the SS rings did.
Per service manual piston to wall clearance limit is .010".. mahle race cast is/was .0015-.002". I set my new blocks between .002-003"..

Keep in mind my engines ran at 50-75% duty cycle on average at a ~400rwhp rating...

Avg daily driver weekend hauler might see 25-30% avg duty cycle.. which the point could easily be made lighter duty cycle substantially longer mileage life

Thanks Again, Moly it is, rather than trying to find another block I would rather replace rings. What is drop of a fleece? Thanks

 

[Bdsankey]

I am confused, I thought those where the same as what Jeremy Wagler is using and they had oval bowls. Sooo is there a race cast oval bowl and can someone post a part number?

Thanks Again, Moly it is, rather than trying to find another block I would rather replace rings. What is drop of a fleece? Thanks

There are many piston manufacturers. Mahle makes 3 types of pistons for our engines. OEM style replacement, motorsport cast, and motorsport forged pistons.

Oval bowl pistons are done by "Fingers". His pistons are based on the Mahle motorsport cast or forged pistons (you choose, obviously forged is more expensive) that are final machined minus the bowl/piston tops (compression height). He then machines them to his bowl profile to your desired compression. He also can add valve reliefs as well during that process.


The pistons referenced above that Jeremy Wagler stated they use are the OEM Mahle replacement, not a motorsport piston.

 

[Gentrysgarage]

Thanks Bdsankey yet again for posting! That clears it all up in one post! As you have suggested I will be using a cast piston, delipped is out. So my choices have boiled down to 1st choice is a Fingers oval cast Mahle motorsports, and a tie for second place being the pistons that Mr Wagler use and the race cast motrsports. I wish I could do a poll for the 2nd place contenders the only reason for considering them over Finger is soley based on $$$ as from everyone's feedback they seem to be the best.

On Another note, are the Mahle pistons sized perfectly? When I was last building engines in the 90's we would sometimes have to send sets back as they weren't exactly .010/.020 etc oversize and even the pistons in sets didn't even match in size. The brands I remember where TRW and Speed Pro, never had a problem with Arias or when the Keith Black Hypernuematics came out.

 

[1FastBrick]

The pistons of today are much more consistent. Mahle Spec's a .002 PTW clearance and the race cast pistons I just received were exactly .002 under a .020 over bore. I didn't measure every one in the box but the ones we did measure were consistent.

 

[malibu795]

I am confused, I thought those where the same as what Jeremy Wagler is using and they had oval bowls. Sooo is there a race cast oval bowl and can someone post a part number?

Thanks Again, Moly it is, rather than trying to find another block I would rather replace rings. What is drop of a fleece? Thanks

Fleece performance did the machine work at the time there's few more shops that do a great job now... Wasn't so common then..

Fingers makes them.. and sells through various vendors

 

[JoshH]

There are many piston manufacturers. Mahle makes 3 types of pistons for our engines. OEM style replacement, motorsport cast, and motorsport forged pistons.

Just to clarify Brad's statement. There are 3 major categories as he mentioned, but within the OEM style pistons, they make 3 distinct different styles. One is made for the 01-05 LB7 and LLY. They make another for the 06-10 LBZ and LMM, and they make a third style OEM replacement for the 11-16 LML. I've never tried to use an LML piston on an earlier style rod, but I know the pin on an LML rod is narrower than the later piston, and there is more of a gap between the pin boss on the piston and the edge of the rod when you use a Motorsport or other piston designed for an earlier rod with an LML rod. I can't say for sure that a piston made as an OEM replacement for an LML will work without interference on a non-LML rod.

 

[PureHybrid]

Just to clarify Brad's statement. There are 3 major categories as he mentioned, but within the OEM style pistons, they make 3 distinct different styles. One is made for the 01-05 LB7 and LLY. They make another for the 06-10 LBZ and LMM, and they make a third style OEM replacement for the 11-16 LML. I've never tried to use an LML piston on an earlier style rod, but I know the pin on an LML rod is narrower than the later piston, and there is more of a gap between the pin boss on the piston and the edge of the rod when you use a Motorsport or other piston designed for an earlier rod with an LML rod. I can't say for sure that a piston made as an OEM replacement for an LML will work without interference on a non-LML rod.

Have you ordered any of these before? In the online catalog from Mahle I'm not seeing a right / left bank for the LML piston like they do for the LB7/ LLY