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Hello all! My name is Cary and I live in Kodiak, AK. Not many 7.3 mechs here. I have an early model 1999 F350 that I have owned for about 16 years. It has been a great truck. I kept good care of it and ran synthetic oil most of its life. It has 365K on the engine. Original HPOP and injectors, very little blow by. Truck runs good. My problem is it keeps bending a push rod . Not sure of cylinder number or intake/exhaust but passenger side next to firewall, the second rod from firewall. I replaced the push rod and the truck ran well for about 2 days and then it bent. Really bad bend. Replaced again, broke rocker arm after an hour of running. I am thinking collapsed hydraulic lifter. Replaced again and flushed the engine with marvel mystery oil ran engine for a while. Seemed to be good. Replaced engin oil. With in one day of light driving rod bent again. Of course every time the rod bends the engine starts missing and belches volumes of blue smoke.
The old truck is well used and I got my money out of it 4X over. Not good resources in Kodiak to do a top side rebuild. I would like to keep the truck for a little longer for light duty. I am just not ready to sell it for parts. Kind of like putting down an old hound you have had for 16 years.
I know there might be things going on in the engine that I have not thought of or don't understand so I am throwing it out there for any Ideas. Any help would be greatly appreciated!!
 

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you might be onto something with that Marvel and the pr lasting longer maybe try something even more aggressive like Archoil 9100
I had a truck that bent and spit push rods .. the valve guide was sticky and that was all she wrote

I held that valve in place with rope and pulled the valve retainer and springs ,, I made a cup to hold some sea foam around the valve guide and ran the valve in a drill moving it up and down in the guide until it spun freely

good luck
 

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Bet those were exhaust valves
not uncommon with a turbo charged engine and a lot of running hours to wear the exhaust guides
carbon/soot will be forced into the gap and cause binding
only fix is to replace the valves and guides
 

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in my case they were newer Edelbrock heads ( under 1000 miles but not a daily driver )

just some bad fuel . high temps and and running lean
 

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. Not sure of cylinder number or intake/exhaust but passenger side next to firewall, the second rod from firewall.
That is an INTAKE valve, #4 cyl.
Piston-to-valve contact is what is bending the push rod.

My guess is that you have weak valve springs (or possibly a BROKEN spring which can be easy to miss in a visual inspection). When the engine gets on boost, the valve is blown open because of the weak or broken spring, and contacts the piston.

Another scenario: Is there any correlation between the push rod getting bent with a high-load, large throttle, or high-rev event? Ie, you fix the push rod and it is fine for a few days but the first time you "get on it" it bends the push-rod again? If = yes, I'd be thinking valve springs.

Next time you have the valve cover off, pull a couple of other rockers on the other cyls. Take something like a hammer and push on the valve with the handle end. (Don't hit the valve with the hammer!). Compare the pressure of #4 Intake with other intakes on other cyls. If #4 is weaker, there's your cause.

Valve springs live in a harsh environment. They have a finite life. Think of what happens when you bend a wire coat hanger rapidly: Eventually it breaks. Valve springs are similar.

TL;DR Look closely at #4 Intake spring. I'll bet it's broken. 365K miles can do that. If you find it IS broken, change them all, and the hound will live to hunt another 16 years. Valve springs can be changed with the heads installed. You need compressed air and an adapter to screw into the glow plug hole to keep the valves up with the springs off.
 

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Discussion Starter #6
Wow!! what great information!!! Thank you very much!! I was ready to send the truck to the bone yard but now I have a great director to go in! What you have said makes great sense. ZMANN though that it might be a sticking valve. I will be able to check both at the same time. I would sure love to get my truck back. It will take me a few weeks to get this done but I will repost and let you know how it turns out. Thank you all again for the help!!!
 

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Dave P's ghost knows his 7.3's very well
I bet on his answers being spot on every time

honestly sometimes my input is just to give a thread traction and bump it to the top lol
 

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Dave P's ghost knows his 7.3's very well
I bet on his answers being spot on every time

honestly sometimes my input is just to give a thread traction and bump it to the top lol
Hello ZMANN and Dave P's Ghost! Well it took me longer than I thought to replace the valve springs as I was so busy at work through the holidays that I did not start the project until a few weeks ago. To make a long story short I ended up pulling the engine out as I had to pull the head on the same side as my bending push rod for unrelated reasons. When I got the head off I could not believe my eyes! After 365 K miles the cross hatching in the cylinder walls was still visible! No wear there! I replaced all the valve springs on both heads. The older spring were noticeably weaker than the new ones. I was certain this was my problem. While I had the engine out I replaced all the push rods and added new glow plugs. I binged and bought a new KC turbo and new up pipes. I put it all together and got it started and it sounded real good. in the test drive I had very little power due to known turbo exhaust leaks that I will get fixed. On my 2nd test drive I tried pushing the RPMs some and as the engine spooled up I heard the dreaded clack clack sound of a rocker arm banging on a push rod. Before I could back off the push rod gave way. Immediate loss of power and volumes of blue smoke out the tail pipe. No doubt the push rod on #4 cylinder intake valve. Well I have to admit I am a real dummy for not inspecting the or replacing the hydraulic lifters while I had the head off. I am a victim of my own desire to get it done quick over get it done right. I am about to give up but only about. I dread pulling the engine again. Does this sound like a lifter failure and if so can the lifters be accessed by pulling the intake manifolds and valley pan and not the heads? Your advise is greatly appreciated!!
 

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If you dig into it again and find that it is the cylinder #4 intake pushrod again, the only thing I can think of would be the lifter. Unfortunately the head will need to come back off to get at them


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AYUP, seen carbon build up on the stems to the point of sticking, usually the guides are shot

would be easy enough to check the travel on the rocker arms, if you have a dial indicator
or just by watching and comparing to the others on that bank, as the engine is rotated
 
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Sure sounds like a bad lifter in the end. At 365k the valves are probably beat to death too. I'm in the middle of a rebuild and I had to buy all new valves and seats to bring the heads back.. All of this can be done without pulling the engine though. With the short block in good shape I would recommend pulling just the heads and have them gone through by a good machine shop. You'd be surprised at how reasonable it can be. I had new valves seats, guides, 3 angle valve job, and a .002 clean up cut for about $750 for the pair plus parts. I bought OEM valves and cups from RiffRaff. The lifters I bought were actually Ford lifters for a 6.4. They are the same lifter and cost less than the 7.3 part number. That lifter kit is 8C3Z-6C329-B. They come 4 to a kit and are around $60 per. The part numbers for the rest:
Intake valve: Ford F4TZ-6507-B
Exhaust Valve: Ford F4TZ-6505-C
Valve locks: Ford F4TZ-6518-A
Oil end rail plug orings: Ford GZ-08-006

All available from vendors on this site. I bought mine form RiffRaff Diesel.
 

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I don't understand how a lifter can be the root cause of a bent push rod. Lifter function doesn't correlate with bent push rods. The push rod is bending because the load on it is exceeding its design strength. The lifter is always going to 'hit' the push rod with the same amount of force. Something is going on on the other end of the push rod.

Misalignment can cause a bent push rod. As long as the loads are directly along the axis of the push rod, it is strong as hell. Just a bit off column and the rod isn't nearly as strong. (Think of a plastic beverage straw: If you push directly on it in column it will go right through the lid. If you get it slightly off center, it kinks and bends). Worn guide plates, worn rocker arms, etc that allow the rod to wiggle off-column....
 

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I don't understand how a lifter can be the root cause of a bent push rod. Lifter function doesn't correlate with bent push rods. The push rod is bending because the load on it is exceeding its design strength. The lifter is always going to 'hit' the push rod with the same amount of force. Something is going on on the other end of the push rod.

Misalignment can cause a bent push rod. As long as the loads are directly along the axis of the push rod, it is strong as hell. Just a bit off column and the rod isn't nearly as strong. (Think of a plastic beverage straw: If you push directly on it in column it will go right through the lid. If you get it slightly off center, it kinks and bends). Worn guide plates, worn rocker arms, etc that allow the rod to wiggle off-column....
That's true, and a collapsed hydraulic or worn hydraulic piston within a lifter will cause an alignment problem. A worn hydraulic lifter will not be able to maintain the hydraulic cushion its designed to. You'll actually cause the lifter to disengage the push rod at a certain rpm because the hydraulic pressure cannot be maintained because the piston is worn. This will cause a huge valve lash gap and when the lifter begins to rise again it reengages the push rod at who knows what angle. Revving the engine will bend the rod. While your in there, I'd install some Smith Brothers chrome molly push rods. I would also inspect the cam lobe to be sure its not having a problem.
 

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I had a lifter in my 4.3 S-10 DD fail in the way you describe above. It was unable to maintain pressure internal and "collapsed" which introduced about 100 thou of clearance into the valve train. It clacked like crazy, but did not bend anything.

I've had a 327 (only old farts remember this gem of a SBC) bolted to the stringers of my ski boat for 45 years. I only use the boat 1 or 2 trips a year but for a long time was suffering through one particular valve would bend the push rod from time to time. This went on for years, until the valve stem got damaged, and it wouldn't even hold to get it on the trailer. The push rod would bend right away when started. I removed the head, took it to my guy to get the valve stem fixed, explained the on-going problem and he pointed to the guide holes in the head. They were badly worn. We drilled the head holes out and installed later model "guided" rocker arms from a 5.7 Vortec. It has run flawlessly now for 4 years since that repair.

Anecdotal, to be sure. And neither engine was a 7.3. But in the scenario you cite where a "bad lifter" can cause a bent push rod it didn't, and the case I cite where things aren't kept in column because the wear was on the other end, it did.

Cheers.
 

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The only reason I've brought that up was It happened to me with a High performance ford 200. Those long push rods were good at being bent with the least little stress, until chrome molly ones were used. Believe me, a nitrous injected straight six can generate some torque, if you can keep it together. fun little 1/8 mile rig though and pretty cheap to run.
 
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