LMM: Rotating assembly ?

H

huey

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Okay, I need a little help selecting parts. I have an 08 LMM with 140,000 miles and a cracked piston. I am in the process of rebuilding it and I just want to reliably tow my camper again while making 400 to 425hp. I have towed the same camper all over the Southern US for the past 3 years trouble free. Will this combination work ?

Mahle cast pistons 0.020 over bore
Callies Durastar crankshaft
My stock LMM rods
All balanced together

Thanks, Huey



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paint94979

paint94979

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huey said:
Okay, I need a little help selecting parts. I have an 08 LMM with 140,000 miles and a cracked piston. I am in the process of rebuilding it and I just want to reliably tow my camper again while making 400 to 425hp. I have towed the same camper all over the Southern US for the past 3 years trouble free. Will this combination work ?

Mahle cast pistons 0.020 over bore
Callies Durastar crankshaft
My stock LMM rods
All balanced together

Thanks, Huey



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If it were mine...
Fingers Oval Bowl Pistons
Brand New Stock Crank
New Stock LMM Rods
ATI Balancer
Crank and Cam Keyways
Balance
New Bearings
 
ikeG

ikeG

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huey said:
Why do I need new LMM rods ? Can I just reuse mine ?


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Your build will be perfectly fine for your intentions. Assuming you meant mahle motorsports pistons. A good machine shop can verify if your rods are good.

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JoshH

JoshH

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I second what ikeG said. Mahle makes a couple of different lines of cast pistons. They have the OE replacements that are like what were used in the LB7 and LLY, and they have the motorsports "race cast" pistons that are beefed up a little over stock. For a couple hundred dollars more, I would go with the motorsports pistons.
 
ikeG

ikeG

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Maybe a better question is how/why did your piston crack? Towing at hi power level and or poor tuning? Or bad injector?
I'd get the injectors tested for sure. Where are you from huey?

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H

huey

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ikeG said:
Maybe a better question is how/why did your piston crack? Towing at hi power level and or poor tuning? Or bad injector?
I'd get the injectors tested for sure. Where are you from huey?

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It has the typical crack that I see all over the internet. I Don’t think it is tuning as it has been on the same tune pulling the same camper for 3 years. Could be a bad injector and I plan on having those tested. I am from Kentucky.
1bfba845c3257c51916467a0e40d3fd1.jpg



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JoshH

JoshH

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huey said:
It has the typical crack that I see all over the internet. I Don’t think it is tuning as it has been on the same tune pulling the same camper for 3 years. Could be a bad injector and I plan on having those tested. I am from Kentucky.
1bfba845c3257c51916467a0e40d3fd1.jpg



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What kind of tune are you running? The spray pattern on the piston bowl tells me it is either a high horsepower tune or the timing is off a little.
 
Chevy1925

Chevy1925

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JoshH said:
What kind of tune are you running? The spray pattern on the piston bowl tells me it is either a high horsepower tune or the timing is off a little.
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the last two engines ive done have been "small/mild tunes" with spray patterns just like that or worse. once they get the truck back together, they come back by and you can hear the damn timing in them. one was an H&S, other was a "custom dsp5". They have since changed tuning lol.

i can see oil temp being an issue only if it makes pressure drop below 28-29psi so the squirters are not working. if pressure is up, 260* oil temp shouldnt cause this.
 
JoshH

JoshH

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It was proven years ago that the squirters don't really turn off at low PSI with hot oil.
 
Chevy1925

Chevy1925

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JoshH said:
It was proven years ago that the squirters don't really turn off at low PSI with hot oil.
Click to expand...

and honeslty, i have never seen oil pressure drop that low even at 2k rpm and 280* temp. lowest ive seen is 30psi on mine and most stock turbo trucks wont get that hot oil temp wise. 260* is average out here on small tunes.
 
H

huey

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It is just a light tow tune and ran with it for a long time, at least 50,000 miles. A bad or worn injector makes more sense to me. I had to drive the truck approximately 2 miles after the failure to get off the interstate highway in the North Carolina mountains which may have affected the pattern you see with all the oil going through it.


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