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piston and rod replacement

PunziRacing

Member
Joined
February 1, 2016
Messages
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City, State
Long Island, NY
Year, Model & Trim Level
2001 Ford F250 SD
I am replacing one piston and rod assembly due to my son hydrolocking the engine. Has anyone attempted or knows of someone who successfully replaced one piston/rod assembly and what i should look out for in my attempt,I should let it be known the engine only had 4500 mi and was a direct replacement from ford.2002 4.0 SOHC. Any help would be awesome and if any pics are needed just let me know. I have not removed heads yet, I am waiting on tool.
 



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Bent connecting rod

IMG_0696_zpsimmfgouq.jpg
 












The force necessary to buckle a con-rod like that is enormous. I see no reason why you could not replace just one piston and rod, but would strongly suggest checking the crankshaft and it's main bearing journals for bending, misalignment, other damage. The aluminum block, being much less rigid than cast iron, likely distorted quite a bit, when the rod was bent. Check the head very carefully, also.

How did one cylinder become filled with water? Did the damage occur when the engine was just being cranked or was it running? I can't imagine cranking forces being generated high enough to bend the rod. imp
 






according to his friends he was on the gas through a very large puddle when the engine just stopped. What it looks like to me is the cylinder filled, the rod bent then the piston seized on the down-stroke against the crank. So in other words the rod shortened and the bottom of the piston skirt smashed against the crank counterweight forcing the engine to stop. If you can see in the photo the rod did not come in contact with the side of the counterweight which is hopefully my saving grace here, the aluminium piston took most of the damage. so far i am only out the 220.00 i spent on the cam tool and I hope to get the head off this weekend to inspect and will post anything i find.
 






If you have the cam timing tool you are ahead of the game. Just remember all the tty bolts need to be replaced. i think you are looking at around 150 bucks for head bolts alone.
 






I found them on Amazon Fel Pro brand for 30$ Per head.
 












So my OTC tool kit came in but before i start i would like to confirm i do not have any bent valves, Will a leak down test confirm this? Also once the heads are off i should be able to measure deck height and see if i have any additional bent connecting rods, correct? Are there any other procedures i should perform before i take the heads off?

Thank you
 






Leak down test should confirm and leaking and or bent valves.

It might be a good idea to have the heads redone anyway if you plan on keeping the rig.

If you are going that deep into the engine to replace one rod, why not pull the lower block and get it all over with?

If your luck is like mine if I fix one 4 months later it would smoke another one.
 






I just picked this engine up from ford ($4000.00) and it has less then 5000mi on it, That's the only reason why i just want to replace whats broke. Everything else was completely refurbished or replaced by ford.
 






Gotch.

Makes sense now.

Old school trick for checking for leaking valves with heads off.

Flip them over on their back side and pour a little gas in the combustion chamber.

Look for the gas to run out of the ports.
 






From the way that rod is bent in the picture I hope you didn't twist the crank.
 






From the way that rod is bent in the picture I hope you didn't twist the crank.

Pretty much what I meant. Or worse. But I understand the desire to save a $4000 investment if possible.

Wondering why any valves at all would be bent? Unless I'm missing something here, if enough water got in one cylinder to buckle it's rod, it's likely SOME got in several others, but not enough in time to do damage; the one hydrolocked piston would have stopped the works REAL quickly.

A guess would be if the engine were turning high rpms when it drank water, much more damage might have been done. I could see possibility of a bent crank, in which case piston height at top center would be different from one cyl. to another; definitely a good thing to check. imp
 






QUESTION: During the time the damaged piston/rod was on its compression stroke and bending the rod, it should not have been possible for another piston to be in a closed valve full(water)cylinder because one of the valves would always be partially open or the piston would be on the down stroke, is this correct?
 






If you think about the mechanical physics of the engine it doesn't seem possible to bend a closed valve because it seated.

A valve is usually bent at the stem due to impact damage.

From the pictures of the one bent rod I would check the next rod in the firing order because that cylinder may have been on its way up on compression stroke and gotten a water slug too.
 






UPDATE:
Installed (1) new piston and (1) rod from ford, put the engine back in and started right up with a loud knock coming from the #6 cylinder (the parts i just replaced). so i take the engine back out and measure the piston and it turns out the reman engine was bored 50mm oversize and ford sold me a standard piston now i go back to ford PISSED OFF because i gave the ****er the old piston to match up, they refund the money for the wrong piston and tell me they cant get the correct one. So i go back to The machine shop i used to press the pin on the rod and start looking for (1) 50mm oversize piston and luckily we find someone who has in stock, put everything back together last week and installed the engine over the weekend and it started right up and runs perfect. So too answer my own question.....YES you can replace the (1) bad rod and piston as long as you carefully inspect the rest of the engine and measure your parts before you install ...not after like i did !
 






UPDATE:
Installed (1) new piston and (1) rod from ford, put the engine back in and started right up with a loud knock coming from the #6 cylinder (the parts i just replaced). so i take the engine back out and measure the piston and it turns out the reman engine was bored 50mm oversize and ford sold me a standard piston now i go back to ford PISSED OFF because i gave the ****** the old piston to match up, they refund the money for the wrong piston and tell me they cant get the correct one. So i go back to The machine shop i used to press the pin on the rod and start looking for (1) 50mm oversize piston and luckily we find someone who has in stock, put everything back together last week and installed the engine over the weekend and it started right up and runs perfect. So too answer my own question.....YES you can replace the (1) bad rod and piston as long as you carefully inspect the rest of the engine and measure your parts before you install ...not after like i did !

50mm is almost 2 INCHES! Rather a large over-bore, I'd say. 5mm is a bit under 0.200", that's possible, but not likely, because it would mean you stuck a piston in a cylinder which was nearly a quarter-inch too small. No way you could have done that. So, maybe 0.5mm? 0.020", twenty-thousandths of an inch, still a pretty sloppy piston fit, but possible to miss by eyeballing. So you ran an engine with a piston loose by 0.020", very possible. Piston "slap" must have been pretty amazing. You have gone through a lot of trouble, give you credit for sticking with it. Next time, beg, borrow, steal, or buy a couple of measuring tools, like inside and outside micrometers to check parts fit before buttoning things up.

Glad this turned out OK for you, and that you let us know. Been 6 months or so, but I recalled the discussion.

QUESTION: During the time the damaged piston/rod was on its compression stroke and bending the rod, it should not have been possible for another piston to be in a closed valve full(water)cylinder because one of the valves would always be partially open or the piston would be on the down stroke, is this correct?

@PunziRacing 6-cyl. eng. gets a compression stroke in some cylinder every 120 degrees of crank rotation, (I think!). Judging by the "buckle" in the damaged rod, a guess would be that the "slug" of water sealed in that cylinder was less than 1" thick, so the piston was pretty near the top, minus an inch. Next cyl. getting ready to fire would be just a bit more than 120 degrees away, say 150. Even then, it's intake valve would have already been closed, and it was starting upwards on compression, so, yes, water might have been in the next cyl. ready to fire. BUT, even if it was ready to smash another rod, the one being mashed stopped the crankshaft pretty abruptly, would be my guess. But before the next slug of water squeezed? Who the hell knows? How fast can a revving engine be stopped, without breaking something in two? Wish I knew. I am guessing the amount of power needed to stop all that spinning mass in less than one crank rotation would be incredibly high, enough to break the block in half.

If my analysis here sounds wrong, please tell me! This sort of technical **** intrigues me! imp
 






Every rebuilt engine that I've known of is bored over 0.030" (0.762 MM.)

Here's what sealed power shows as piston options for an '05 4.0

image.png
 



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IMP, the sad thing is i have a good set of micrometers that is how i realized the piston was too small when i took it back out. I am very disappointed in myself for not taking the time to measure. and by 50mm i did mean .50mm which turns out to be .020 in oversize.


Number4, My experience is mostly with 2 & 4 stroke motocross engines and normally a quick hone is all that is needed to bring a cylinder back to life as long as there was no catastrophic failure. but that is no excuse i should have miked the cylinder anyway.
 






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