Knocking after new heads

[stacker]

The mechanic just finished putting new heads and a new piston, injectors and well, now he tells me i got a knock, he thinks it piston slap on the cylinder with the new piston, said he's going to pull the pan again tomorrow and take a look, Any suggestions. Thank

[john8662]

If the mechanic didn't check the bore size and the piston size before he threw in another piston, find another mechanic.

You aren't going to "see" piston slap from the bottom.

Since the heads have been off, the injection lines should have been removed, so an injection line could also be mixed up, which will make a knocking sound.

J

[tommac95]

>going to pull the pan again tomorrow and take a look

he may be checking the rod bearing setup , or the cylinder/web crack-situation.

[stacker]

Talked to mechanic today he said it definitely had a piston slap when he looked at the piston he changed (hun....hun) now what isn't #8 the one he changed it didn't have a slap before the head problem why now. any suggestions:confused:

[JohnC]

he said it definitely had a piston slap when he looked at the piston he changed (hun....hun) now what isn't #8 the one he changed ...

Huh?

Are you saying he is telling you it is a different one slapping?

Piston slap is a sort of hollow knock like you'd hear if you hit a hollow log with a mallet. Is that what you're hearing?

First, pistons slap at the top of the bore. I can't imagine how he could tell by looking at them, especially from the bottom.

Second, the only way I know to induce piston slap "all of a sudden", other than installing a piston too small for the hole, is to damage the piston, like by letting something get between it an the head when it comes up. The deformed piston then could slap.


Unless he dropped something into one of the cylinders, my money is on the injectors...

[stacker]

Just and idea since the mechanic raced to the machine shop i wonder if the piston he put in was wrong and maybe to small or tall -10 for a decked block since my block suppose to only have 40k miles. thanks:confused:

[john8662]

From the sounds of this the engine had previously been remanufactured.

It is entirely possible that the engine's deck surface has been cut and either "topped" reduced height .010" pistons were used or .010" thicker head gasket was used with STD height pistons.

Do you have the old piston? Why was it replaced?

Could very well be the piston is touching the head and or valves.

J

[stacker]

My guess is since it was the same piston knocking, he's probably put the std height piston in an hopefully since it never ran long. it will only need a .010 piston. Thanks wish me luck.