By on April 16, 2013

Mu-een (from Cape Town, South Africa!) writes:

Hi I would like to know what is the difference sound of a tappet noise, or bad rocker, or a piston slap. Thanks regards.


Sajeev answers:

I suspect that –for most engines– piston slap is a deeper, more resonant sound than an out of whack tappet.  Pistons are bigger and buried further in the engine (usually) than tappets, it’s gonna have a different sound by design.  Conversely, you could easily isolate the two sounds with a decent mechanic’s stethoscope, or with a cheap one. So for whatever vehicle you own down in Cape Town, try isolating the noise with a stethoscope…or maybe just a loooooong screwdriver against the cam/valve cover on the top of the motor.

Now on to the important implications of this letter. Put another way, OH MY DAMN SON U KNOW WHAT THIS MEANS? We got us some Piston Slaps from North America, South America, Europe, Asia, Australia…and now Africa!

TTAC RULEZ THE WORLD! This is Panther Love with an LSX-FTW swap: a fantastic combination of wonderful things in a singular moment.


Wait…is Antarctica a continent too?

AND they drive cars down there?

Do they read TTAC?


We were sooooo close to world domination!




Send your queries to [email protected]com. ESPECIALLY IF YOU ARE FROM ANTARCTICA. Spare no details and ask for a speedy resolution if you’re in a hurry…but be realistic, and use your make/model specific forums instead of TTAC for more timely advice.

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14 Comments on “Piston Slap: Is it Piston Slap? Ja-nee, baby!...”

  • avatar

    Remember that the camshaft(s) turn at half the speed of the crankshaft, so a noise at “engine” speed will usually be from the lower end, while a noise at half “engine” speed will be valvetrain related.

  • avatar

    Piston slap will often get quieter as the engine warms up and the aluminum pistons expand more than the iron cylinders, thus reducing clearance.

  • avatar

    Excellent points from both of you! This is why I love the blog format, everyone’s brainpower makes for a far better answer!

  • avatar

    And rod knock is a deep sound that never goes away (until it breaks).

  • avatar

    Piston slap is really a problem with older (30 – 50 years) engines were the engineering of pistons and rings in the cylinder were not as tight as it is now. Worn rings + big and small end bearings would result in the pistons quite literally slapping the side of the cylinder. If I am not mistaken the symptom is a rocking engine… more than normal. Modern engines will have a many more problems than that a long before, like burning oil from worn rings (white smoke all time).
    Cape Town huh! Go find a Ford Cortina 3.0 V6 (XR6) and listen to the ticking the engine makes. Those are tappets. Those motors were notorious for that and would start making tappet noises about an hour after being set.

    • 0 avatar

      Unfortunately, not all modern engines were immune from piston slap; my 1997 D16Y7-powered Civic has it bad, along with excessive oil consumption during normal driving. In hot weather if you drive it hard, it uses no oil and the sounds go away, for the reason you mention.

      And for grins & giggles, google ‘GM V8 piston slap’ and start reading!

      • 0 avatar

        Beat me too it. My Chevy Suburban used to sound like an 80’s Powerstroke until it warmed up — and this is with under 80,000kms on it. The piston slap and GM’s repeated attempts to duck the problem pretty much made sure it the last time I would ever buy a GM product.

        • 0 avatar

          Chrysler 2.2/2.5 litre engines from the K car era could develope piston slap as well at higher milages…my had a distinct rattle at idle after the car passed 200K miles…

  • avatar

    My BMW 2002 has a pretty worn out engine and bad piston slap when cold. I was told its also caused or causes the piston to go out-of-round.

  • avatar

    x2. Piston Slap was the same reason I ditched my G8 GT. 30k kms and it sounded like a diesel until it warmed up. In the winter that was 10+ minutes of driving My OCD couldn’t take it. GM tried to duck it and they just shrugged their shoulders. Never a GM for me again.

  • avatar

    They all sound like a large woosh coming from your wallet.

  • avatar

    LSx swap into a pather! Have the gods no mercy!!!! That ain’t panther love. Panther love would be FRPP 5.0 MOD block with a stroker crank making it dang close to 330 cubes topped off with a set of Trick Flow 2v heads and a nice set of cams.

    I swear if I ever get a heap of money, I’m doing a road-runner(Boss 5.0) MT-82 and 8.8 swap into a nice old 67 Nova.

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