piston hitting the head

[ashes29]

I am currently fixing an engine knock in a friends car(same engine as in my profile), and after removing the rag I found jammed in the throttle body(previous shop it was at sucked hard) i removed the head and piston #4 is hitting the head, not enough to dent or scuff either but enough to keep the high spots on the piston and the corresponding spot on the head shiny. Any ideas on what could be causing this? I don't want to tear down more than i have to. also the bearing on the #4 rod was the work done at the previous shop...i have been told that if they reversed the rod it could make it do this.....thanks

i have thoroughly gone over the head and everything is fine there, no bent valves, head gasket was good, mating surface is not warped

[huafist]

Originally Posted by ashes29

I am currently fixing an engine knock in a friends car(same engine as in my profile), and after removing the rag I found jammed in the throttle body(previous shop it was at sucked hard) i removed the head and piston #4 is hitting the head, not enough to dent or scuff either but enough to keep the high spots on the piston and the corresponding spot on the head shiny. Any ideas on what could be causing this? I don't want to tear down more than i have to. also the bearing on the #4 rod was the work done at the previous shop...i have been told that if they reversed the rod it could make it do this.....thanks

i have thoroughly gone over the head and everything is fine there, no bent valves, head gasket was good, mating surface is not warped

I don't see how a piston could make contact with a head and not cause damage. Given the velocity a piston posseses when approaching TDC, if it actually made contact there would be MUCH more than a "shiny" spot. It would also sound like the End Times in the engine when it ran. There's no way they could have reversed the rod unless they took the piston out, had the wrist pin pressed out, and pressed it back in backwards - it's possible, but highly unlikely. Taking a piston completely out to repalce a rod bearing is like reaching around the world to scratch your ass, it doesn't make sense. If they'd put the rod bearing cap on backwards, the engine probably wouldn't turn at all, and if it did it wouldn't well. Neither situation would make the piston make contact with the head.
If this really *IS* the case, the engine needs to be completely torn down and rebuilt from the ground up.

[BlandAnalogy]

you couldnt have said that any better. it's nice to see somebody that uses key terms as well...
piston slap is no friend of mine and i hopefully will never have to deal with such a problem.

[ashes29]

the piston at tdc looks as though it doesn't reach above the cylinder(checked with a straight edge across the top of the block...but at any rpms at all while running it is a loud knock...one reason for the no damage as of yet may be the engine has only been ran maybe 15-20 seconds since the bearing was replaced then it was towed to me.

[ashes29]

also the piston does not wobble as it comes up the cylinder and now that i have the oil pan off i checked and there is no play in the bearing, the rod and cap were installed correctly....should i just reassemble it and hope for the best?

also could the rag which was completely blocking the throttle body have caused this?