Piston Slap problem??????

[krummel45]

I beleve i have piston slap i went to get my car worked on at the local chrysler rip off shop and i asked him what the noise was i was hearing around 1100 rpms on up. He went and got the service mang. ANd they did a test with the spark plugs by pulling them out and located the problem to pe piston slap in the number 4 cyclender.

I have wisco forged 8:8:1 pistons and the sound doesent go away.

Is it normal to have piston slap, noise, with forged pistons?

What can i do to make sure that is the problem?

thanks

 

[Groomz]

Piston slap can only be avoided with proper machining. Sounds like whoever did the install didn't check the tolerences too well. Some Ford 5.4-liter V8s get piston slap from the factory, so it can even happen on completely stock motors. LS1s have this problem too ( for some ). Maybe a colder thermostat? Less expansion from less warmup. Just a random thought.

 

[krummel45]

so will it be ok to run on the engine has over 2800 miles on and if it would have happened from the machine work than wouldnt it allready have gone out?

the compretion test read out at 140 for three and the last at 136.are these a good number or not?

 

[DSMJim]

Yes and no. It depends on the clearances used then your motor was built. JE always recommends a little larger clearance because of the material the pistons are made from so they are always noisy but Weisco generally are not.

If your motor was built loosely then it will be noiser than a stock motor. As long as you have compression the same across all cylinders who cares what it sounds like.

A B16 with ARIAS pistons we did with a little larger clearance was noisy as hell but didn't require much break in and made killer power.

 

[Groomz]

I got 150psi across the board on 8.5:1 compression and 130K miles. Maybe its the carbon in the combustion chamber though. It seems that those numbers are low. Any forged pistons will experience piston slap to a degree ( heard or unheard ), but the tolerences play a big part in whither it happens when the car is warmed up. I would just drive it and not worry about it. Nothing you can do other than another rebuild. Just drive and have fun.

 

[krummel45]

what could cause the lower compretion?

I went out and drove it for a while and let heat up, the higher the rpms the louder it gets. So the forged pistons do slap and how loud before it becomes a concern?

Im only runing 12psi but am woried if it will blow once it really gets ctranked up.

 

[DSMJim]

If its gonna blow because of bad clearances it will do it at low boost too because even low boost is a lot of cylinder pressure. If it's ok now, then don't worry about it.

There isn't anything you can do to fix it short of re-boring your motor and putting in newer larger pistons which makes your useless now. So you have nothing to lose if you blow a ring out or whatever so who cares it you blow it up. Blow it up or not its gonna cost to change, so drive it and enjoy.

 

[dsm1kenobe]

About piston slap...

It occurs during start-up and/or when the engine is cold in forged pistons applications. The pistons smack against the cylinder wall because the piston/block (mostly the pistons) haven't expanded to their use temperature. Race motors (more so than street motors) are prone to slap at unloaded RPMs as the piston to wall clearances are huge; Race motor piston slap will go away when the motor is loaded - different story for a street motor. In this case, if you're motor isn't built right, the piston will slap no matter what temperature your pistons/block is at because the clearances are wrong.

Other than rebuilding your bottom end, run as high a boost as you can and your slap might go away. You'll have more power too..darn.

 

[dsm1kenobe]

Originally posted by Groomz
I got 150psi across the board on 8.5:1 compression and 130K miles. Maybe its the carbon in the combustion chamber though.

150psig for 8.5:1 CR is low. You should be getting 170 ish. Carbon in the combustion chamber should raise CR.

 

[2.4 turbo Hyped]

I have wiseco 8.8:1 forged pistons with a stock bore on a 2.4 liter sonata bottom end. I have piston slap when the motor is cold only in the 0 vacuum range. Once I get the motor warmed up (steady highway driving maintaining 1400 degrees f) the slap goes quiet, barely able to hear it. The motor has 180 psi on all 4 cylinders, makes tons of power, burns NO OIL. I figure if it was gonna blow it would have blown at 25 psi that I use daily on pump gas. DRIVE IT TILL IT BLOWS!! Pistons are cheap for these motors as well as the blocks for them. Keep a spare block on hand like I do in case you ever need to build another beast. Have fun and smoke hondas thats what its all about. Regards, Sean

 

[sunflashx]

My Ross pistons are .006 piston to wall clearance and any sort of piston slap I have is gone within minutes as soon as the operating temp starts to come up, it requires no actual driving. It's almost not even noticable, if you weren't listening for it you probably wouldn't notice. It was torque plate honed on a Sunnen ck10.

It was my understanding that 6 thou was fairly loose. While you have Wiseco piston, and mine are Ross not sure how comparable it is, but thought another data point might be helpful.

If you are only having "piston slap" in one cylinder, you most likely have a problem. If the block was built correctly, all the cylinders would do any slapping that they were going to do at the same rate.

 

[dsm1kenobe]

Wiseco recommends 3 thou.

.006 is not what I remember Ross recommending for p to w clearance.

 

[sunflashx]

Originally posted by dsm1kenobe
Wiseco recommends 3 thou.

.006 is not what I remember Ross recommending for p to w clearance.

It's what Ross recomends, and was confirmed by Marco @ Magnus, from where the pistons were purchased.

 

[2.4 turbo Hyped]

I guess the clearance depends on the metallurgy of the pistons. I had .004 on all 4 pistons. Sounds more like a valve tick than a piston slap. Very very quiet.