Piston slap

[TheRedBlur]

my motor developed a nasty tick before it was stolen, now that it's recovered I'm going through the motor to see what the tick is coming from, the lifters are all o.k., no unusual wear on the pushrods, and all the rockers are pretty tight. but then again, I could still find something if I looked closer.

my question is about piston slap.

what exactly is it?
how does it develop?
does it even develop or slap from the beginning?
does it sound a lot like a pushrod bounicng off a valvecover?

I don't want to have to pull the engine out again, I did that last year, twice.

 

[Rick 91GT]

Piston slap aooccurs when the piston moves/rocks in the bore.

Measure the bore with a bore mic, PTW (Piston to Wall Clearnace) should be around .002.-003" Usually you do not hear excessive slap until it is over .005

You say the lifters are ok, how did you check them?

 

[thumper460]

How many miles?? did they run out of oil?? Boosted??? Piston slap isnt easy to tell.. usually a skirt will crack allowing the piston to be loose in the cylinder and "slap" the wall.. or maybe the skirt fell off and is laying in the bottom of the pan.. This is NOT a comon failure.. however, look for the simple things.. and header leak will make a "tick", loose plug... cracked header or exhaust... remember the " KISS" approach.. cool??

Just me....................

Thumper
( KISS.. Keep it simple stupid .. no slam just the facts.. LOL)

 

[Rick 91GT]

KISS..never heard that..lol

 

[Modular2v]

kiss??? keep it simple stupid?

 

[89CopCoupe]

Also, certain engine configurations necessitate the use of short skirted pistons which rock in the bores and "slap" can be quite audible at certain rpms.

 

[Foxfan88]

my motor slaps and its alwys from the same place. Cant really hear it much, only on start ups and randomly sometimes.

We had a really expierenced friend LISTEN to the exhaust and he could tell it was piston slap.

 

[TheRedBlur]

well, I can feel the ticking when I have my hand on the valvecover. I have a ticking lifter, I know what that sounds like, I have had broken a rocker stud, so I know what a pushrod bouncing off a valvecover sounds like. I'll check the p/s plugs anyways jsut to be sure, but I don't see any evidence of a broken plug or a loose exhaust gasket. my gaskets are tight, I've had lots of header gasket leaks, they usually leave suit around the leak.

one of the reasons why I think it could be piston slap is because I recently had a set of fel-pro 1250's **** on me, resulting in coolant sucking into my runners. I worry that with my relatively high compression (9.8:1) that having something more dense than air/fuel being compressed, that it might have done some damage to a rod or wristpin. I think I might find a bad wristpin if I pull my motor and flop her upside down.



keep the idears coming though!

 

[Rick 91GT]

Usually when you get a large amout of coolant into a cylinder you bend pushrods or valves...

A compression test may tell you what is wrong

 

[TheRedBlur]

lol, I have a HUGE amount of blowby going on. I pulled my oil cap for a better listen, and I was getting a pretty strong wind coming out of it.