Mahle piston tolerances ?

Redrock2000

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Being a disabled veteran on a fixed income this build will be done over time. With that said I've found the best price for pistons delipped and coated individually. I'm wondering if Mahles tolerances are close to the point where I can buy a couple of pistons at a time so I can have the block bored the
balance done with my forged rods and finally the final hone done when all 8 are purchased. I was going to wait till I refinanced my house but the truck has been sitting to flippin long. My goal is 600 hp 250/ 1 or 200 sticks, Adrenaline, and either a S369 or 467 turbo. The plan is to invest in the high $ stuff after refinancing. I'm 53 years old and this is no kids dream. Thanks for all information y'all can provide. Please don't say get a used motor I've been looking for 1 forever. When I have found one that isn't outrageous ( $3000 with 2 dead cylinders) or I don't have the cash in hand.
 

Zeb

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Mahler tolerances are great in my experience, but my opinion is if you’re on a fairly tight budget, you’d be much better off buying a set of uncoated, lipped pistons and running them. Dilipped pistons are not necessary on a 7.3, and coating them is a waste of money.
 

Redrock2000

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Mahler tolerances are great in my experience, but my opinion is if you’re on a fairly tight budget, you’d be much better off buying a set of uncoated, lipped pistons and running them. Dilipped pistons are not necessary on a 7.3, and coating them is a waste of money.

How and why are my questions as far as the delip and coated? Thanks
 

Magnum PD

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Are you doing ceramic coating or anti friction? I vote for delipping them
 

Magnum PD

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The piston rings will be what needs to be a in certain spec. Need to have all pistons balanced to the lowest weight.
 

Magnum PD

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Probably gonna need to shave the block and head. If you do that, then need .010 decked pistons
 

Redrock2000

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My concern was piston to cylinder wall clearances. I wasn't sure how close in size Mahle casts and machines their pistons. I'm now wondering about the delip and coating myself as I have seen stock 7.3s crack pistons. I can measure and grind for ring end gap and my plan is to balance the complete rotating assy. My local machine shop said it depends on the bobweight as to weather they can balance it or not. Thanks all
 

Magnum PD

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Do you have the block out and apart? Need to bore it out at least .010 I would think. Then you know what size pistons you need
 

Redrock2000

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Do you have the block out and apart? Need to bore it out at least .010 I would think. Then you know what size pistons you need

May end up having to sleeve it. Have 3 cylinders that have quite a wear ridge. I haven't measured it yet but hope to clean them up at .030 bore. I found out the hard way you can't baby bad injectors.
 

lincolnlocker

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Mahler tolerances are great in my experience, but my opinion is if you’re on a fairly tight budget, you’d be much better off buying a set of uncoated, lipped pistons and running them. Dilipped pistons are not necessary on a 7.3, and coating them is a waste of money.
Wow. This is the first thing i think you have posted about that i dont agree with... lol.. it is most certainly not a waste of money. I had cracks in all 8 of my pistons. I know lots of guys over the years from all sorts of forums that had the same issue. Granted tuning was a lot different and has progressed over those same years but i highly recommend doing at minimum a delipped piston. Ceramic coat them will only help in the long run but that isnt necessarily a must. If going more than 600 then sure.. He is shooting for 600hp and is going to have 6-7 grand in a motor to get it there. Why skimp on the small stuff?

live life full throttle
 

lincolnlocker

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May end up having to sleeve it. Have 3 cylinders that have quite a wear ridge. I haven't measured it yet but hope to clean them up at .030 bore. I found out the hard way you can't baby bad injectors.
First off, thank you for your service sir!!

How many miles on that block? Dont let the wear ridge bother you. Thats just where the rings stop. Lol.

live life full throttle
 

Redrock2000

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I'm going to have to put some pictures of the pistons and rings up. The tops of the pistons looks like weld splatter and the top compression ring was burnt/broken on the one piston I have out. My service to this great country was a pleasure and I'm thankful for your appreciation
 

Zeb

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Wow. This is the first thing i think you have posted about that i dont agree with... lol.. it is most certainly not a waste of money. I had cracks in all 8 of my pistons. I know lots of guys over the years from all sorts of forums that had the same issue. Granted tuning was a lot different and has progressed over those same years but i highly recommend doing at minimum a delipped piston. Ceramic coat them will only help in the long run but that isnt necessarily a must. If going more than 600 then sure.. He is shooting for 600hp and is going to have 6-7 grand in a motor to get it there. Why skimp on the small stuff?

live life full throttle

I posted too quickly, and didn’t word it well at all.

I think that ceramic coating the tops is a waste.
On delipping them, I don’t like a full delip (straight bowl wall) because it contributes quite a bit to white smoke when cold idling. Roll the lip back, but don’t totally eliminate it. It is very good to have a small lip to help that fuel/air mixture to turn and burn especially when the motor is cold and idling.
I have not seen any companies offer the pistons done the way I like them, (I do my own whenever I build a motor) so that is why I generally discourage it on a 7.3 or 6.0.
 

lincolnlocker

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I posted too quickly, and didn’t word it well at all.



I think that ceramic coating the tops is a waste.

On delipping them, I don’t like a full delip (straight bowl wall) because it contributes quite a bit to white smoke when cold idling. Roll the lip back, but don’t totally eliminate it. It is very good to have a small lip to help that fuel/air mixture to turn and burn especially when the motor is cold and idling.

I have not seen any companies offer the pistons done the way I like them, (I do my own whenever I build a motor) so that is why I generally discourage it on a 7.3 or 6.0.
Ahh 10-4

live life full throttle
 

Redrock2000

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I really appreciate y'alls input and I do understand your point is the way you're pistons are done a precision machining or just a slight deburr with a cartridge roll. Also I can see the skirt dry lube wearing off but why would the heat barrier coating on top be a waste? Doesn't it prevent heat sink through the piston crown? Does it not last too? Thanks again
 

Zeb

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I really appreciate y'alls input and I do understand your point is the way you're pistons are done a precision machining or just a slight deburr with a cartridge roll. Also I can see the skirt dry lube wearing off but why would the heat barrier coating on top be a waste? Doesn't it prevent heat sink through the piston crown? Does it not last too? Thanks again

As far as what I do with the lip, I put them in a lathe and push the lip back, then change tools and under cut it (the lip) to blend it into the current bowl wall.
I want the lip to look like it did originally, just closer to the bowl wall so that the opening into the bowl is larger.
If you don’t under cut it, you end up with a tall vertical wall on the lip and that pretty much defeats the purpose of trying to keep some of the lip there.

On the ceramic coat on the top of the piston, it comes off very quickly. I can’t see how it prevents heat sink thru the crown when it’s not there.
A friend tore down a 6.4 after 3,000 street miles that had ceramic coated pistons put in it, and you couldn’t tell they had ever been coated. Yes, I saw them before the pistons were put in and they were coated.
I have heard that over and over again from guys that have put in coated pistons and then tore down the motor soon afterwards. That is why I consider it a waste of money.
 

Zeb

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Here is a couple pictures that hopefully clarify what I’m trying to explain. Granted, they are 6.0 pistons but the same principle applies.

First picture is what the lip looks like pushed back but not under cut.

Second picture is when it is completed.
 

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Redrock2000

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Is .250 the amount you take off? That seems quite a bit if not what are the amount to remove from the lip and back cut? Again I really appreciate your time I've built many hi performances gassers never a diesel till now. I have a good friend who is a great machinist so I'm sure he would be able to do the delip and undercut. And with what you have said about coatings together would save me quite a bit of money. Btw I have read similar results from other builders concerning coatings but didn't know that was the norm. What do y'all think of investing into aftermarket rods with the money saved and the fact that this is a long term project? As always thanks for the info.
 

Zeb

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Is .250 the amount you take off? That seems quite a bit if not what are the amount to remove from the lip and back cut? Again I really appreciate your time I've built many hi performances gassers never a diesel till now. I have a good friend who is a great machinist so I'm sure he would be able to do the delip and undercut. And with what you have said about coatings together would save me quite a bit of money. Btw I have read similar results from other builders concerning coatings but didn't know that was the norm. What do y'all think of investing into aftermarket rods with the money saved and the fact that this is a long term project? As always thanks for the info.

0.250” is how tall the lip is on a 6.0 piston if you open the bowl up and don’t undercut the lip.

On a 600hp 7.3 I’d run factory forged rods, good tuning, and put the $2,300-$3,000 that rods would cost into other parts.

On a totally unrelated subject Redrock, I use to live at Hale Center and hauled thousands of tons of feed and ingredients out of Purina, Pyco, etc there in Lubbock.
 
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Redrock2000

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0.250” is how tall the lip is on a 6.0 piston if you open the bowl up and don’t undercut the lip.

On a 600hp 7.3 I’d run factory forged rods, good tuning, and put the $2,300-$3,000 that rods would cost into other parts.

On a totally unrelated subject Redrock, I use to live at Hale Center and hauled thousands of tons of feed and ingredients out of Purina, Pyco, etc there in Lubbock.
To be honest Id love to go all out and give some of the kids around here some competition Lol but Id rather reliability and practicality. No kiddin on the Texas part of it. I worked for Pyco for a day. Lol Where do you live now?
 

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