My 5.4 I sent to one of the best shops in town to to have my engene rebuilt by a third party, ok. It comes back with a knock before I get from & my mechanic. They, the machine shop said they used an after market piston.

The problem: cold start is fine & after a few minutes it is a knock & tap that is gone soon.

This mechanic said about piston slap with newer engiens (.0001)
& it has to warm up & the teflon coated pistons expand??

Excuse me but I bought mine new & never had this or I'm sure yours.

Any way this is going back.....What do you all think???

 

teflon coated pistons?!?!?!? didnt know they made teflon coated pistons lol guess if you ever threw the motor, you could always poach an egg on em! LOL but to my knowledge, if the piston is "slapping" something, then its probably already damaged beyond repair... and now your going to need a rebuild.... again lol there is no such thing as a properly rebuilt motor "knocking" or "pinging" under normal usage... you have to make sure that you run it 1000 miles VERY gently, no harsh acceleration, no towing, and certainly, no revving... i would go a full oil change, but thats just me.... but if you got the truck home, let it sit for a while, and turned it on and it was knockin? nope.... he needs to take care of that, and i would be sure to let him know that it would be better to do it now than later, seeing as future use will just have him paying you for a brand new engine.... because if you crack the block, or twist your connecting rods, or slap the valves/head... you are going to do a LOT of damage, and i wouldnt trust a motor to be rebuilt after having THAT much damage... i would just tell him he has to furnish you with a new one.... you went in there (im assuming) because either a head gasket or your piston rings were bad.... not because you "blew up" your motor... and thus you shouldnt have to bare the burden of driving around with a motor that has been "wrecked" since you didnt wreck it before hand... if hes responsible, he will have to furnish you a new motor... end of story...

 

Teflon coated pistons have been around for a few years.They lower cylinder wall temperatures and at the same time are far more slippery then conventional pistons.
When I use to race/build/rebuild small block Chevy engines (about 30 engines) I would run the engine at 1500-2000 rpm the first 20 minutes of its life to properly break in the cam and its components.Then,ide take the vehicle to the interstate to vary my speed from 30 mph to 10 mph,up to 60 mph,down to 20 mph,to load/unload,to seat the rings.I did this in numerous cycles.I then drained the oil (30 weight) and did a oil change. I was taught by my dad,who was a racer,to run the engine to however you are going to use it.If you are using it for towing,start towing with it.Daily driving,run it like that.Racing,***** to the walls! Dont baby the engine.Drive it however you are using it for! BTW,change the oil again at 500 miles then go the normal intervals.

 

i always heard (from many high performance gurus in the area) that breaking in a new motor for 500 miles is essential, otherwise improperly seated rings, and valves and such have the chance to burn out quicker... just because they were new, and introduced to extreme conditions right off the bat. just what i heard, sounds right... why would you want to dog on a brand new motor?

 

Do you think when Joe Farmer goes to his local Ford dealer to buy a F350 to haul his cattle they tell him,"Ok Mr Farmer,dont haul any of your cattle for 500-1000 miles for fear of ruining your engine"..... NO!
Why? Because the motor was already broken in,like I said earlier.Maybe not like I do them,but similar.
You ever been to an NHRA event? Do you think those top fuel and funny cars have an area to "baby" there engines until ready to race? NO! They build them,break them in,then race them! Just out of curiousity,how many engines have you built or have broken in?

 

3.... but you said it, they were broken in, and break in times are usually 500 miles... or XX amount of hours... im sure the factory has some way of breaking them in....

 

What you described sounds suspiciously like piston slap. Not a MAJOR concern, but one that should be addressed. Personally, I'd ask for a rebuild (again, at no charge) to replace the pistons with different ones.

Oh and Teflon coating works well to prevent carbon buildup.

-Flea

 

radiohead,
I just read this post. If the pistons are forged then some piston slap is normal. I suspect if they are coated pistons they may be forged. I am shopping pistons now and am looking for a high silicone content forged piston to MINIMIZE the start up piston slap.