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.
Mu-een
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?
NO???
We were sooooo close to world domination!
Send your queries to sajeev@thetruthaboutcars.
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.
Piston slap will often get quieter as the engine warms up and the aluminum pistons expand more than the iron cylinders, thus reducing clearance.
The same can be true for tappets too. As the oil warms up, they will quiet down.
Excellent points from both of you! This is why I love the blog format, everyone’s brainpower makes for a far better answer!
And rod knock is a deep sound that never goes away (until it breaks).
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.
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!
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.
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…
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.
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.
They all sound like a large woosh coming from your wallet.
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.
I’m with you and I’d cram an FE in into say…a C4 ‘Vette. Maybe a solid front axle just for fun.