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Old 09-10-2019, 10:25 AM   #1
frankencummins
 
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Duramax Pistons

What pistons would you all suggest for around 800hp in an LBZ build? I've heard the buzz around some non-conventional shapes on other forums & read several threads on here that seem to contradict that. What's the verdict? Wide & flat leaving more meat in the middle taking more out of the lip to maintain bowl CC? Or go with the non-conventionally shaped bowl that puts more over the pin but cuts closer to the oil galley to maintain CC? I thought at one point Smoke'em had a rather extensive thread on this topic in here. For the life of me I can't find it.
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Old 09-10-2019, 10:33 AM   #2
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Desired use for the truck?
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Old 09-10-2019, 11:03 AM   #3
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Toy/ test & tune warrior/ drive to work occasionally. Motor is going in a 2WD 2500 truck so no heavy work.
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Old 09-10-2019, 11:10 AM   #4
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Finger's (Jon's) oval pistons for that application. If it was a truck seeing regular street driving duty, then regular Mahle round bowls. Just my opinion.
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Old 09-10-2019, 11:21 AM   #5
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Fingers oval cast pistons
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Old 09-10-2019, 12:49 PM   #6
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The injector cone angle and bowl design are intended to work as a pair. Run the widest, shallowest bowl you can, that plays nicely with your cone angle.
No injector has an oval cone angle, so even tho those pistons might be slightly less likely to crack above the wrist pin, a conventional round bowl is a better choice.

Last edited by bracker8040; 09-10-2019 at 12:50 PM.
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Old 09-10-2019, 04:52 PM   #7
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Jon's oval bowls may not be as efficient at burning fuel from a fuel/air mix standpoint but they are more than just "slightly less likely to crack." They have proven to be substantially less likely to crack.

If it's not a truck needing the best fuel efficiency, a set of Jon's cast oval bowl pistons would definitely be in my build.
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Old 09-10-2019, 04:54 PM   #8
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I've been around trucks with his pistons and they dont have the haze people think they would or say they've had. These were all big fuel trucks too. Imo if you're making enough hp to worry about pistons fuel mileage shouldnt be a concern.
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Old 09-10-2019, 06:09 PM   #9
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My comment was not made with fuel mileage in mind.
A mismatched cone angle/bowl design will hurt power.
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Old 09-11-2019, 08:59 AM   #10
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Quote:
Originally Posted by bracker8040 View Post
My comment was not made with fuel mileage in mind.
A mismatched cone angle/bowl design will hurt power.
Which is the other side of efficiency, something more efficient = more power. If a person is in a competition vehicle trying for every last drop of power, something else might be a bit better but there's also plenty of Jon's pistons in serious competition vehicles.

So, if ultra efficiency isn't what's needed/wanted, Jon's pistons are fantastic. Which a 7-800hp build is prime candidate for them IMO.
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Old 09-11-2019, 09:43 AM   #11
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Bretts c10 is running jons pistons still isnt he?
I know a friends 1400hp capable truck that's running them, and two others that make around 9 to 1k that's run them for years with no issues.
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Old 09-11-2019, 11:24 AM   #12
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Quote:
Originally Posted by bracker8040 View Post
The injector cone angle and bowl design are intended to work as a pair. Run the widest, shallowest bowl you can, that plays nicely with your cone angle.
No injector has an oval cone angle, so even tho those pistons might be slightly less likely to crack above the wrist pin, a conventional round bowl is a better choice.
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Originally Posted by bracker8040 View Post
My comment was not made with fuel mileage in mind.
A mismatched cone angle/bowl design will hurt power.
I think Jon would beg to differ with you on a lot of what you're saying, but there are always tradeoffs in building high-hp diesels.
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Old 09-11-2019, 12:57 PM   #13
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I did a 900hp build for a customer with similar needs/plans as you stated. In that build I opted to use a set of delipped mahle cast pistons. Turned out decent, runs good and hasn’t had any issues in 3years with the 40k he’s put on it.
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Old 09-11-2019, 02:27 PM   #14
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Quote:
Originally Posted by TheBac View Post
I think Jon would beg to differ with you on a lot of what you're saying, but there are always tradeoffs in building high-hp diesels.
I expect he would. Heís the guy building the pistons after all, and he wouldnít do it if he didnít think it was a good idea.
Iím not disputing the fact that they are less likely to crack. But, a mismatched cone angle/bowl design is a bad idea. For example, look at the issues the Cummins guys have when they use 6.7 pistons and the wrong year 5.9 nozzle above it. More smoke, more heat, less power, etc.
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Old 09-11-2019, 02:38 PM   #15
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Quote:
Originally Posted by bracker8040 View Post
I expect he would. He’s the guy building the pistons after all, and he wouldn’t do it if he didn’t think it was a good idea.
I’m not disputing the fact that they are less likely to crack. But, a mismatched cone angle/bowl design is a bad idea. For example, look at the issues the Cummins guys have when they use 6.7 pistons and the wrong year 5.9 nozzle above it. More smoke, more heat, less power, etc.
That's a bigger downside than what we're talking here though. The "narrow" part of the bowl isn't any smaller than factory. If you want to make power and have the pistons last, oval bowl is the only option besides a forged piston. Yes the Mahle race cast are just fine (which is what Jon machines his from) but for the ultimate cast setup you'll need oval bowls.

A delipped LB7 piston might last for a while if not ragged on constantly, but an upgrade would be recommend by almost all builders, and if you're dropping money on the race cast parts, might as well go oval bowls.
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Old 09-11-2019, 07:13 PM   #16
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I don't think I'll be doing de-lipped LB7's. I've seen a lot of good from the ovals & people making over a grand on them. Which is very encouraging. My issue is the same as mentioned above, they don't do anything to address injector overspray which was an issue on this engine even in stock form, see pic. Eventually it's going to cause erosion. Which I saw in 3&5 of the stockers coming out of this motor at 88k miles. Does he de-lip, or at least mitigate lip on the ovals? I guess it could be as simple as narrowing the cone angle on the injector & running ovals.
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Old 09-11-2019, 07:46 PM   #17
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Somebody was running a ****-ton of pulsewidth on their tuning on that engine. Cripes.

Jon doesnt have a website. Give him a call. Hear it from him. Fingers 412-638-9026
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Old 09-11-2019, 09:01 PM   #18
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Somebody was running a ****-ton of pulsewidth on their tuning on that engine. Cripes.

Jon doesnt have a website. Give him a call. Hear it from him. Fingers 412-638-9026
X2, run bigger injectors and turn the pulse back to make your power goal. Usually a max effort tune on an LBZ needs upwards of 3000us (stock inj.) that'll put a hurting on pistons even if you have the air to keep it cool
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Old 09-11-2019, 09:05 PM   #19
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Quote:
Originally Posted by frankencummins View Post
I don't think I'll be doing de-lipped LB7's. I've seen a lot of good from the ovals & people making over a grand on them. Which is very encouraging. My issue is the same as mentioned above, they don't do anything to address injector overspray which was an issue on this engine even in stock form, see pic. Eventually it's going to cause erosion. Which I saw in 3&5 of the stockers coming out of this motor at 88k miles. Does he de-lip, or at least mitigate lip on the ovals? I guess it could be as simple as narrowing the cone angle on the injector & running ovals.
Get with a good tuner that has experience tuning with the oval bowls, and run what they recommend.

Danville Performance is my suggestion, Mark has pushed the limit with these oval pistons
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Old 09-11-2019, 09:10 PM   #20
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That was stock pulse, no tune. Motor was in a fleet truck with no tuner guys. Mark & Danville have it together with the ovals. I read the whole thread where Fingers rolled them out & have drooled over some Danville videos.
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