LMM: Short Block Assembly

[huey]

Attempting to put my short block together and ran into sone concerns. My new Mahle performance cast piston rings have a ring gap of 0.015 and Mahle says it should be 0.020 minimum . GM says it should be 0.012 - 0.018. Comparing the rings they look just like the factory GM rings. My bore is 4.075 +- 0.0005 with the torque plate off. What is everyone one setting there gap to ? I am only looking to make a 450 HP tow rig.

 

[Ron Nielson]

Doesn't make sense. The rings and the ring gap have to be coordinated. The pistons have a gap and the rings need to fit in the gap with designed clearances. Mahle, or any piston manufacturer, will have different style pistons and different specs for their rings for that particular piston style. No mix and match specs. Find the correct spec for your pistons and disregard all the rest.

 

[huey]

Well the rings say they are not file to fit and after measuring the pistons, the piston to wall clearance is right on spec at 0.002

 

[Chevy1925]

Send those rings back and order a set from SoCal Diesel. Mahle has terrible quality control on rings I’ve found. If they are the 41909, they use an iron upper ring, not a stainless steel like stock. They wear out faster due to that.

 

[malibu795]

Send those rings back and order a set from SoCal Diesel. Mahle has terrible quality control on rings I’ve found. If they are the 41909, they use an iron upper ring, not a stainless steel like stock. They wear out faster due to that.

They'll where very fast!!! Like 30k miles and done fast

 

[huey]

Will Mahle really give me credit on just the ring set from the piston kit ? Wish I could tell which ones they were 4075MDK-D doesn’t come up as a good part number.

 

[Chevy1925]

Will Mahle really give me credit on just the ring set from the piston kit ? Wish I could tell which ones they were 4075MDK-D doesn’t come up as a good part number.

Call them. When I spoke with the rep they refunded me after shipping them back and I bought new ones

 

[ripmf666]

Will Mahle really give me credit on just the ring set from the piston kit ? Wish I could tell which ones they were 4075MDK-D doesn’t come up as a good part number.

Here is the number you need for replacement rings.
42160-020

 

[TheBac]

Hmm...you guys make me want to do a comp test on my engine now, 50,000 miles after the rebuild.


BTW, somehow this thread was in Garage Sale. Strange. Moved to Engine Building.

 

[huey]

Here is the number you need for replacement rings.

42160-020

Just got off the phone with Mahle and they tell me 42160 supersedes 41909 and 4075MDK-D supersedes the 42160. The 4075MDK-D is the latest from just a couple months ago.

 

[Chevy1925]

Just got off the phone with Mahle and they tell me 42160 supersedes 41909 and 4075MDK-D supersedes the 42160. The 4075MDK-D is the latest from just a couple months ago.

good luck. you're gunna get a run around. either way you should be making it a point about the rings NOT being file to fit and gap being off IF the block truely has the correct bore.

when i assemble engines, i check everything again just as how the machine shop would so that 1. i make sure they have done the engine to my specs and 2. i have ammo if a part is incorrect and finger pointing starts.

 

[ripmf666]

Just got off the phone with Mahle and they tell me 42160 supersedes 41909 and 4075MDK-D supersedes the 42160. The 4075MDK-D is the latest from just a couple months ago.

Checked new number is good. There is 5 sets at mahle would get back on the phone and start working on them to replace the set.

 

[huey]

Getting ready to install my new crank gear and I was told to heat it up in a oven for 30 minutes but I can't remember what the temperature should be ?


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[huey]

So no one has advice on a crank gear install ?

 

[M.A.M.]

300 @ 30 minutes will work, doesn’t have to be a certain temp, just give it some heat.


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[PureHybrid]

Just because a ring isn't listed as "file fit" doesn't meant you won't have to file them at all to get the specs you want. But like James said, double check the bore measurements, with a TQ plate if they honed it with one.

 

[huey]

I checked everything with a bore gauge and only the top of the bore was affect by the torque plate around the bolt holes. Being I don’t have one, it looks like I can just push the ring farther down in the bore (2 to 3 inches from the top) and file fit the gap at that location.

 

[huey]

I'm using new stock TTY main bolts from Merchant and I am confused on what to do for lube. I have read that I should not use additional lube because the bolts come with a pre-applied molybdenum disulfide coating. I have also been told to use a light coating of oil by 2 different engine builders. What is the right thing to do ? Also which torque method is everyone using (1st Step 72 lb ft 2nd Step 97 lb ft 3rd Step 60 Degrees) or (1st Step 74 lb ft 2nd Step 90 degrees) ?

Thanks, this forum is a life saver for the Duramax.



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[Chevy1925]

Little engine oil on threads and then 72/97/60*