If you dont like the piston slapping sound just put a supercharger on it.

 

Yeah, i've had forged pistons before (though, they've never made a sound like this) and am completely okay with it... if it is for real normal. When the dealer takes two weeks to just give me an answer... that's what makes me uneasy.

Here's another thread I posted with an updated odd sound video... It made this a little while back now and hasn't since.
https://themustangsource.com/f726/po...-302-a-529208/

 

Hello alex3610,

Welcome to the forum! My name is Deysha with Ford Service. Have you brought this up to your dealer? If not, I recommend you bring it in and speak to your service manager to make sure there’s nothing else going on. He is in the best position to ensure a proper diagnosis, and will be able to provide available options and/or coverage for any work needed.

You can schedule an appointment online here. Let me know the outcome.

Deysha

 

it doesn't sound at all like that....
Anyone know what a bad start would sound like?
As in, after in engages, car starts, and then it not fully releasing. As if it had a bad spring in it?

 

Quote:

Originally Posted by zwede

Forged pistons making a clattering noise when cold is well known to us old hot rodders.

Unfortunately there simply is no technical foundation underlying the observation by some that “forged” pistons make more noise during startup than “cast” pistons. Piston slap, which causes the perceived noise, occurs when excessive clearance exists between the skirt of the aluminum piston and the inner bore of the (usually) iron bore of the engine block. (block sleeves included). Four variables effect this running clearance and thus the production (or not) of piston slap noise-

1. The cold build clearance the manufacturer sets between the piston Outside Diameter (OD) and the cylinder bore Inside Diameter (ID).
2. Piston skirt design and length relative to its diameter.
3. The piston and cylinder bore thermal expansions (material property alpha).
4. The thermal response of the piston and cylinder bore during warm-up (material thermal conductivity).

All of these variables are considered (and tested) by the engine designer when developing an engine. Of primary concern is the piston/bore geometric relationship while at operating temperature. Start-up, as the engine materials go from room temperature to operating temperature and shut-down, as the component materials cool to room temperature are considered but are not as important as the hot running clearance which effects engine efficiency and emissions.

Certainly the designer would insure the piston would not expand too quickly on start-up which could “stick” the piston in the bore if the piston OD grew larger than the bore ID. Same consideration on shut-down. That’s why you start out with a cold build clearance between the two components. The alpha of the aluminum piston is considerably higher (meaning it grows more when heated) than the cylinder bore material. And at colder start-up temperatures, the cold clearance is greater and thus a higher likelihood of piston slap occurring. This cold engine start (at lower ambient temperature conditions found in winter) appears to have the owner’s concern.

Design variables 1 and 2 are solely geometric considerations not tied any casting/forging material characteristic. Variables 3 and 4 DO pertain to material characteristics but the alpha and thermal conductivity differences of our forged piston material and that of a typical cast pistons (either eutectic or hypereutectic cast alloys) are infinitesimally small. See chart below.


In fact, a given aluminum alloy can be either cast to shape or forged to shape. The casting/forging manufacturing operation is a process which can be used to tailor material strength and fatigue properties, but the process does not affect “physical” properties of the underlying aluminum alloy such as alpha and thermal conductivity. Thus there is no underlying tendency for a given piston manufactured by a forging process to be any noisier than the same piston made using a casting process. I would opine the old engine builders who seem to harbor this thought are inadvertently comparing engines which have differences in design variables 1 and 2 and thus not an apples to apples comparison.

I am of the opinion the design cold build clearance we have in our engines is on the order of 0.001” diametrical, loose. This (relatively tight) build clearance would tend to limit or attenuate piston slap during a cold start up. I have been told that during development testing the engine/piston design engineers experienced exactly the same noise phenomenon as reported here by some owners. Post teardown inspection showed this slap noise did not cause any piston/bore durability problems and the noise stopped immediately (as owners have reported) once the engine block coolant got to about 180°F. It was like someone flipped a switch on the noise, just as reported by owners hearing this in their cars.

Thus I would agree with the guidance given by Gogoggansgo below-

Quote:

Originally Posted by Gogoggansgo

Glad I could help guys I work at the ford plant so I see all the warranty stuff but piston slap is normal and ask a lightning owner about that. It's normal my friend forged pistons contract over night and they have to expanded this makes a terrible noise nothing u can do.

 

Wow.
If that is the case then... great!?

When it would last 15 minutes (while driving city streets to work), the temp outside was 30-50 deg-F.

I am surprised, though, that it would take THAT long to heat up to just 180 deg-F.

I'm having the dealership inspect the starter next week too.

It does do it EVERY day though still for, at most, a 1/2-sec.

Does everyone's do that?

 

Maybe my hearing is not as good as others but I have never heard pistons slapping on the boss even when cold.

 

Nor have I heard any noise from my Roadrunner engine during startup either. Which is not to say others are just imagining the noise.

The development engine to which I referred which did exhibit the start up noise had a cylinder ID on the high side of its tolerance band with one (or more) pistons on the low side of its dimensional OD tolerance. This relationship produces the highest cold build clearance within the drawing allowed manufacturing tolerances.

If one does experience this piston slap noise and it persists for for a long period (guessing 5+ minutes) I would certainly have the dealer or Ford investigate.

 

Truth comes out.

My dad, some how, is always right and listened to the noise. Instantaneously, he said, oh bad starter. Dropped it off at the dealer on June 12th telling them to just take a look at the starter. Picked it up yesterday, brand new starter. NO MORE SOUND.

Apparently the teeth were worn out on it due to a weak spring or such? Basically the teeth were rattling.

I'm excited to say that since November... this issue is finally resolved. Thanks dad.

So all along, it wasn't the pistons, just the starter. Now it all makes since.

 

We need more guys like that around!