Piston Slap? What is it? eagle/wiseco combo?

[whitesleeperVr4]

OK, What I'm doing is building a block with eagle rods and wiseco pistons. I want this to be is a daily driver in the sense that it's practical and will be reliable, I don't want to have to deal with all the major problems like needing race gas or it breaking in 10,000 miles. At the same time I want this to be able to handle the mods I plan on doing in the future, basically everything. I'm not looking for a 700 hp car, just something I'll be able to enjoy. the reason I'm doing internals now is because I need a new short block anyway. bad things are happening in the old one. first question is I was looking for what others said about this and I kept coming up with piston slap and that confused me, I found that is is due to the block expanding faster than the pistons, but thats really all I could find. I looked in the tech guide, tried searching for it, looked in the FAQs even tried a google search. Nothing told me more about it, Is it bad for a car? will it cause damage to the block over time? would this be a reason for me to not get forged internals? can someone please let me know what their experiences with piston slap are and what they think about it?

 

[jasoncitrano]

Piston slap is caused by pistons that either have no skirt or a reduced skirt. These pistons are very much in favor today as they greatly improve engine efficiency and when they work right, engine life. The problem is, a lot of them aren't working right. To understand piston slap, in an abbreviated version here's what happens, when the connecting rod in a given cylinder gets close to and moves away from the top of its stroke, its angle of travel changes. In other words it swings from one side to the other. In theory the piston's wrist pin should permit this movement without creating a sideways force on the piston.

The problem shows up when the wrist pin doesn't allow absolutely free side-to-side movement of the connecting rod, which in turn causes the piston to rock back and forth. This rocking causes the piston to come in contact with the cylinder wall . . . and you have piston slap. Hope this helps ya.

 

[jasoncitrano]

Just noticed your in schaumburg as well!

 

[herostar]

I've never heard of any complaints from eagle rod owners, or wiseco piston owners either. You should be fine. Oh, also, my JE pistons slapped... I'm going with wiseco's now and am still running eagle rods.

 

[sbiggi]

Piston slap happens when there is to much clearance between the piston and the cylinder wall. When the rod changes directions at the top of the stroke is causes the piston to rock, and if the clearance is to loose you will hear the skirt hit the cylinder wall.

Forged pistons require larger clearances due to the expansion properties of the metal (because of the high silicon content). Each piston manufacture defines what the clearance should be set at based on the metal they use in their pistons.

You can avoid piston slap if the machinist sets the proper clearance when machining the block.

Excessive piston slap will wear the cylinder wall over time and cause a loss in compression and jack the rings eventually.
Getting the piston skirt coated (polymolly coated) will help avoid cylinder wall scuffing.



Thats off the top of my head....

-Seth

 

[turbospyder19]

To the best of my knowledge, Wisecos are less likely to slap than JEs or others, so I'd say you're fine. Just make sure, as the other guy said, that your clearances are right.

 

[bfdahl]

Piston slap happens when there is to much clearance between the piston and the cylinder wall. When the rod changes directions at the top of the stroke is causes the piston to rock, and if the clearance is to loose you will hear the skirt hit the cylinder wall.

Forged pistons require larger clearances due to the expansion properties of the metal (because of the high silicon content). Each piston manufacture defines what the clearance should be set at based on the metal they use in their pistons.

You can avoid piston slap if the machinist sets the proper clearance when machining the block.

Excessive piston slap will wear the cylinder wall over time and cause a loss in compression and jack the rings eventually.
Getting the piston skirt coated (polymolly coated) will help avoid cylinder wall scuffing.



Thats off the top of my head....

-Seth[/QUOTE

Very well put 90% of the time this is a machine shop issue and not with the product!

 

[whitesleeperVr4]

Thats guys for all the help. From what your all telling me all I need to do is make sure it's all machined right. It also sounds like piston slap is not all that harmful in the long run if the block is made right. Anyone else have any comments still I'm open to hear them.

 

[gixrman]

What you should also know is that when doing a cold startup forged pistons will "slap" until they get up to operating temp. Wiesco even went a step further and offset the wristpin location to combat slap. Proper machining and the right shop always helps too .

 

[1fast97gsx]

FWIW ... I had wiseco 9:1 pistons on eagle rods in my 6 bolt. I had the wall clearances at .0035" which is just a tad more then wiseco suggests even. I got absolutely no slap. I drove it in the winter as well as the summer and it seemed to love those clearances.

 

[ArticNemesis]

6bolt here with eagle rods/wiseco 8.3:1 pistons. The block was clearanced at .003" (which Brian Nutter over at wiseco recommends for a street driven application, as long as you break the motor in properly).

No piston slap here.

 

[JohnTSI]

As said before slap is 90% who machines the block. It is the very reason I changed machine shops. We had a motor with JEs built at one shop, slapped like crazy, they tried to staff it off as it was the pistons fault. Next motor I took somewhere else with JEs again, no slap still running strong. Have had 3 motors built there with JEs no slap at all in any.