Hello,

I am currently replacing the head gaskets on my 1995 3.8L camaro and got down to the pistons and noticed their is a slight amount of movement it can do from side to side and the head tilts ever so slightly if you press on the sides (I'm talking 1-4mm at most). I should also mention that all of the pistons do the same thing so even ware at least.

The cross hatching is fine and nothing looks warped/scraped so I don't think their is a problem but I've never seen pistons have play before but then again this is my first camaro I've broke down. Is this normal?

 

Piston clearance spec normally comes from the piston manufacture due to the material and mass of the piston involved. Cross hatch pattern almost always look good towards the top of the motor. My guess would be what you are feeling is a grove worn in the cylinder from the piston cocking when it is fired. If you pulled your motor and checked the cylinders you would find they are out of round .010” towards the bottom of the cylinder. This is normal wear on 100K plus cars. 4mm (.150”) would indicate a pretty big problem A factory piston is going to have between .004” and .007” clearance. That is straight side to side movement. Add in the fact the cylinder is worn out of round and the fact some of what you are feeling is cocking and 1MM could still be a working motor.

Motors with more the.007 tend to knock on cold startup. Did the motor knock before you took it a part? Did the motor overheat when the gasket went? An overheated motor can do a lot of damage to the cylinders and walls but to get 4mm your cylinders and piston would need to be completely trashed.

 

Good info Gorn. Actually, yes, it does run rough for the first 1/2 second you fired it up (its not a knock, just like a low growl). It did overheat once but the 1/2 second thing was there before that.

I will measure it when I get off work to get an accurate measurement.

Update: I checked the valves, their okay as well..

 

I measured the movement, its 1mm of movement in all directions.