Some would say that piston slap is not so much a problem but a common condition related to the way engines are designed today. The design of the piston skirt is the culprit.
I know several people with vehicles that exhibit piston slap to some extent. They are Chevy's, Ford's, Pontiac's, Old's and so on.
While many think it can be controlled by the viscosity and type or brand of oil, there is no reason for this to be true. Most all of those that say it works to use 20W-50 or some other type are basing that on personal experiences and not on any known or accepted facts.
That said, I am sure other will disagree vehemently.
I think most of the piston slappers are engines with hypereutectic pistons or some kind of lightweight desgign other than cast. The ones that come to mind are the LT1's, LS1's (both truck and fbodies and vettes)and Ford's modular motors. Also if a motor is by design pretty loose than it might do this some. The Jeep 4.0 comes to mind on this one.
I saw a piston removed from a recent hi tech
European engine. The ring pack was cramed together and high on the piston.Same with the pin.Below the pin, where you would expect to find the skirt, well it was there but more like a loin cloth than a skirt.It was obvious to me that this piston would have to be beautifully fitted to a matching precision bore and even then would" flop about' until expansion and stabalization from heat took place.With the small almost non existant skirt, I am sure that there would be slap. We can thank the EPA for all these mods as it is all about reduced friction and better CAFE gas milage. Who cares how long the motor will live?
Thanks guys. But what about knocking? Since that is usually caused by excessive cylinder temps, could certain oils effect heat transfer? Or is the temp only dependent on the coolant and having the right viscosity oil?
[ April 13, 2003, 02:53 AM: Message edited by: spleck ]