All 8 pistons cracked? What happened?

lincolnlocker said:

you two need to get a room!

live life full throttle

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Ya-the kind where only one comes back out...

sootie said:

Ya-the kind where only one comes back out...

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either way works.. lol

live life full throttle

So for the sake of discussion not arguing, how do valve releifs make pistons stronger, even delipping does not make them stronger. Both are removing material thus weakening. Now delipping to remove a potential source of where a crack may start is beneficial, one is still removing material. (personally I feel by cutting valve reliefs all your doing is adding more sharp edges that you were trying to get rid of by deliping in the first place. if you don't need them, why would you want them?)

Now when delipping does everyone remove the same amount, cut the same amount for valve releifs? Etc.

I just reread, it was mentioned that cut and delipping would increase reliability, (I will leave the stronger as I'm sure people may feel it makes them stronger)but there has to be a limit, or it's just detrimental.

sonic blue l said:

So for the sake of discussion not arguing, how do valve releifs make pistons stronger, even delipping does not make them stronger. Both are removing material thus weakening. Now delipping to remove a potential source of where a crack may start is beneficial, one is still removing material. (personally I feel by cutting valve reliefs all your doing is adding more sharp edges that you were trying to get rid of by deliping in the first place. if you don't need them, why would you want them?)

Now when delipping does everyone remove the same amount, cut the same amount for valve releifs? Etc.

I just reread, it was mentioned that cut and delipping would increase reliability, (I will leave the stronger as I'm sure people may feel it makes them stronger)but there has to be a limit, or it's just detrimental.

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Mitigating failure points is increasing reliability. Technically strength is not increased by removing material. Leave them stock and have cracked pistons and valves kissing pistons. Flycut and delip and mitigate those failures-which lasts one longer...


i see your point but i truly believe the OPs issues are not piston strength.

sonic blue l said:

So for the sake of discussion not arguing, how do valve releifs make pistons stronger, even delipping does not make them stronger. Both are removing material thus weakening. Now delipping to remove a potential source of where a crack may start is beneficial, one is still removing material. (personally I feel by cutting valve reliefs all your doing is adding more sharp edges that you were trying to get rid of by deliping in the first place. if you don't need them, why would you want them?)

Now when delipping does everyone remove the same amount, cut the same amount for valve releifs? Etc.

I just reread, it was mentioned that cut and delipping would increase reliability, (I will leave the stronger as I'm sure people may feel it makes them stronger)but there has to be a limit, or it's just detrimental.

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The Keyboard Engineer will chime in shortly............

well personally I went with max force pistons. no valve reliefs, no coating, no modification to piston tops. They do have a " better " top of the piston vs factory. I also run a colt stage 2 cam. I have valve springs. my block nor heads were never decked. ford head gasket. only reason why valve hit pistons is if head are decked, block decked, valve train issue, lifter issue. If set up properly there is no worry, if a lifter fails or your revving it too the moon then perhaps you should have the correct springs, or change your cam profile. (lifter failure you'd have to tear down anyway, so reliefs arnt going to help much) bottom line is id switch cam profile, shorter push rods, different lifters, thicker head gaskets, anything before cutting valve reliefs. unless of course its a race engine that you plan to tear down every season to inspect. (im talking a daily driver, which tows, one takes on holidays, etc) my truck also has zero haze. (it can get down to -40 here in the winter, my truck also starts fine cold, etc)

now tuning, yeah I agree. But also if one cuts a valve relief at .010" or .100" could make a difference.

I tune my own truck and and I also built my engine. (not bragging, just stating that I know exactly what was done to it)

sonic blue l said:

well personally I went with max force pistons. no valve reliefs, no coating, no modification to piston tops. They do have a " better " top of the piston vs factory. I also run a colt stage 2 cam. I have valve springs. my block nor heads were never decked. ford head gasket. only reason why valve hit pistons is if head are decked, block decked, valve train issue, lifter issue. If set up properly there is no worry, if a lifter fails or your revving it too the moon then perhaps you should have the correct springs, or change your cam profile. (lifter failure you'd have to tear down anyway, so reliefs arnt going to help much) bottom line is id switch cam profile, shorter push rods, different lifters, thicker head gaskets, anything before cutting valve reliefs. unless of course its a race engine that you plan to tear down every season to inspect. (im talking a daily driver, which tows, one takes on holidays, etc) my truck also has zero haze. (it can get down to -40 here in the winter, my truck also starts find cold, etc)

now tuning, yeah I agree. But also if one cuts a valve relief at .010" or .100" could make a difference.

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valve to piston contact is an awful lot more common than people think. the insane drive pressures they see can float valves easily on a hot tune-regardless of cam, pushrods and springs (dont ask me how i know lol)

that's were tuning and knowing your **** about your truck come into play. even a frozen ebp sensor due to egr ****** could cause excessive ebp.

btw ive never seen a stock 6.4 crack a piston, the most common thing I ever see on a stock 6.4 is lifter failure. my 6.4 was stock, I bought it as the guy put gas in it and drove it till it would not run. had a lot of miles and hours on it, but the guy did oil changes based upon that. (pretty smart guy until he put gas in it, lol). anyway rockers looked perfect, so I replaced the fuel system and was good to go. Only reason I tore mine apart (much later after the fuel system) was that I had a run of trucks at work that ate lifters and I didn't want mine too. Not to mention I poped head gaskets pulling big hills on a canned h&s tune. thing pulled 15,000 lbs up hill like a champ. I never pushed coolant, but would loose heat once and awhile.

Moral of my story is, stock they don't break as often as people think, as long as their maintained.

sonic blue l said:

that's were tuning and knowing your **** about your truck come into play. even a frozen ebp sensor due to egr ****** could cause excessive ebp.

btw ive never seen a stock 6.4 crack a piston, the most common thing I ever see on a stock 6.4 is lifter failure. my 6.4 was stock, I bought it as the guy put gas in it and drove it till it would not run. had a lot of miles and hours on it, but the guy did oil changes based upon that. (pretty smart guy until he put gas in it, lol). anyway rockers looked perfect, so I replaced the fuel system and was good to go. Only reason I tore mine apart (much later after the fuel system) was that I had a run of trucks at work that ate lifters and I didn't want mine too. Not to mention I poped head gaskets pulling big hills on a canned h&s tune. thing pulled 15,000 lbs up hill like a champ. I never pushed coolant, but would loose heat once and awhile.

Moral of my story is, stock they don't break as often as people think, as long as their maintained.

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agreed.....except the dont break stock as often as you think bit lol

i have logged hundreds of thousands of kms behind the wheel of multiple six fours...they break lol

lol, well I need them to break.

6.7's don't break near often enough. honestly I liked my 6.0l until some asshole stole it and torched it.

I came for 6.4 info, I am not leaving disappointed in this thread lol.

08Stroke said:

So I’d like to get some opinions on what the heck happened here. Less than 45k miles on motor #2 and boom! Cracked number 8 clean across and the other 7 have smaller fracture cracks in them. I’m at a loss. These were fly cut, delipped and coated Mahle pistons. The cracks are all right at the lip of the fly cuts on each piston. The truck was dyno’d at 630whp and is stock fuel and air. No where near a big power truck. Is it just a coincidence that 2 weeks prior new tuning was downloaded to the truck? What’s everyone’s thoughts on this? Also, I’m considering going with the maxxforce pistons this go around. Is that the best option available right now? Who’s got the best pricing? Thanks in advance for any input.

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Who machined the pistons?

Im just gonna say this.



Delipped pistons with valve reliefs aint what caused that failure. Take a pic of those pistons and lets see how much 18° of timng was used.