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Mahle Drop-in Power Pack 2618 Pistons - Horrendous Piston Slap

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57
85
Exp. Type
HPDE
Exp. Level
20+ Years
Michigan
Good lord these things are loud ! Just got my Gen3 5.0L Aluminator clone on the road and was astounded by how loud the piston slap noise is. If you‘ve been following my build thread you’ll know I have been putting together a 2021 Mach 1 I picked up from a Copart auction that had engine damage. I used a new block, crank, Manley rods, and Mahle pistons to duplicate an aluminator for improved durability. I was surprised at the noise levels between 2-3k RPM when lightly loaded. Accelerate or decelerate it goes away but steady state light load it’s very noticeable. Much worse cold of course but still noticeable hot.

Per Mahle spec sheet that came with the pistons PTW clearance should be 0.0023“. Mahle website says 0.0025 - 0.0033. I was right at 0.0025 - 0.0027 so all should be in the ballpark.

I’m currently running 5w30 break in oil and will be switching to 5w-50 soon.

Anyone else have experience with these?
 
1,163
2,121
Exp. Type
Time Attack
Exp. Level
5-10 Years
SoCal
Good lord these things are loud ! Just got my Gen3 5.0L Aluminator clone one the road and was astounded by how loud the piston slap noise is. If you‘ve been following my build thread you’ll know I have been putting together a 2021 Mach 1 I picked up from a Copart auction that had engine damage. I used a new block, crank, Manley rods, and Mahle pistons to duplicate an aluminator for improved durability. I was surprised at the noise levels between 2-3k RPM when lightly loaded. Accelerate or decelerate it goes away but steady state light load it’s very noticeable. Much worse cold of course but still noticeable hot.

Per Mahle spec sheet that came with the pistons PTW clearance should be 0.0023“. Mahle website says 0.0025 - 0.0033. I was right at 0.0025 - 0.0027 so all should be in the ballpark.

I’m currently running 5w30 break in oil and will be switching to 5w-50 soon.

Anyone else have experience with these?
Glad to hear I’m not the only one experiencing this! I have the exact combo built by RPG Race Engines and the noise has been there since initial startup. Countless time spent making sure it wasn’t some other metal to metal contact and finally just came to accept it as part of the forged piston experience.
 
1,163
2,121
Exp. Type
Time Attack
Exp. Level
5-10 Years
SoCal
Same condition for you, 2-3k RPM and you can essentially turn on turn off by changing load with throttle input?
Exactly the same range. I’ve ran 20+ events now and no issues with the short block. Unfortunately discovered oil in the coolant reservoir after a recent event - suspecting head gasket or cracked head. I guess I’ll have the opportunity to look at the cylinders and see if the slap is doing any noticeable harm while the engine is out.
 
57
85
Exp. Type
HPDE
Exp. Level
20+ Years
Michigan
I used those as well. #930258362 - Gen3 5.0 “drop in”

I’m familiar with race engines, my 82GT is very much a race build. However it’s a loud car in general so piston noise is probably covered up.

Guess I’m glad to hear others are having the same experience. First thing that comes to mind is did I screw up the build. So now that I have a bit of reassurance we’ll get a few more miles on the break in oil, switch to 5w50, and then drive it like a rental.
 
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I used those as well. #930258362 - Gen3 5.0 “drop in”

I’m familiar with race engines, my 82GT is very much a race build. However it’s a loud car in general so piston noise is probably covered up.

Guess I’m glad to hear others are having the same experience. First thing that comes to mind is did I screw up the build. So now that I have a bit of reassurance we’ll get a few more miles on the break in oil, switch to 5w50, and then drive it like a rental.
When you had the blocked honed did they provide you with all the measurements and did they have the pistons in hand to verify each piston and mark them to the corresponding hole? The measurements only really mean anything if they are taken while the torque plate is on or a head is torqued and you take the measurements from the bottom end.
 
Are you also sure it’s not the gen3 noise that happens between 2-3k rpm that is widely hypothesized right be harmonics if the DI injectors phasing out and over to the port injectors? Between 2-3k rpm at part/transient throttle and sounds like piston slap/rod knock/not good.
 
Are you also sure it’s not the gen3 noise that happens between 2-3k rpm that is widely hypothesized right be harmonics if the DI injectors phasing out and over to the port injectors? Between 2-3k rpm at part/transient throttle and sounds like piston slap/rod knock/not good.

Agree. Have you heard a stock Gen 3 at those RPMs to compare to the current engine?

Gen 3s are known for their 2k rattle, which sounds alot like piston slap (but it's not) and pretty much happens in every engine of that generation.
 
206
171
Exp. Type
W2W Racing
Exp. Level
3-5 Years
Columbia, TN
I had heard the port injectors on the Gen3 don't come online until 90% throttle and up. It's all DI until 90% throttle and then both injectors come online.

My 2013 stock 5.0l has piston slap when it's cold between 2-3k rpm at mild throttle input. Heavier throttle only makes it louder until it moves past 3500rpm-ish. Oh, my engine has 122K miles on it.
 
My forged 5.2 build has Mahle forged pistons and exhibits piston noise until warmed oil is at 170 degrees. I never put load on it unless it is warmed. Just something that happens with race engines.
Sounds like a stock gen 2/3 piston with a good ring pack is a good bet if you’re not boosted or revving it to the moon. If they can handle 700rwhp boosted, they should handle N/A road racing to 7500rpm.
 
6,363
8,190
Forged pistons.... if they don't slap at least a little, they are too tight. These mod motors really like honing plates, block plates and whatever else you can strap on them to simulate engine stress, including the motor mounts.
Then measure each piston individually, although I suspect the Mahles are pretty dead on.
 
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6,363
8,190
The only thing they let us change in Grand Am was the rods, valve springs and oil pump drive, We could go .020 on the bore to straighten them and that required new pistons, but that wa sit. They had to let the Chevys use a dry sump to keep those engines alive.
 

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