I posted a while back that my block had gone bad and needed a new one, well I found a truck wrecked but running great and started and would pull itself around flawlessly. So I picked it up. I’ve been tinkering with the motor peeping it to go in my truck, got it cleaned, resealed the oil pan and rear main, then put my exhaust manifolds on it. Then I removed all of the rockers to replace the cam springs and injector cups. Well once all that was done I put one side back together and when I went to roll the engine over it got tight. So I backed off. I checked which cylinder was up and decided to remove rockers again. As soon as I removed them I could spin the engine. So I opted to remove the spring I just installed to see if the valve was bent or binding. It seemed fine. Now the injectors are out, so I can’t air the cylinder to see if the valve is leaking by. But at this point I backed off and started looking around. I found several other pushrods bent. So I spun the motor over again to make sure it was good with that one off. It spun just fine. I removed the vent rod and put a straight one in and it would contact. So now I’m at the point where I either pull heads or attempt to get the lifter to bleed some of the oil off so it doesn’t hit if that’s possible. I’m pretty sure this isn’t a normal problem. Any help would be appreciated!

 

Ok so I found some info digging that said put the engine at 11:00 for re assembly so I went out and redid all of them and replaced the bent pushrods and let it sit for a bit and now it turns over just fine without hitting anything. The post I found said this was in the manual and it was to prevent valve jacking. I had left this motor upside down for 3 days while the oil pan cured and now I’m thinking this could have been some of the problem. Still not sure how the pushrods got bent unless at some point it was over revved but with the straight ones if there was a problem I figured they would have hit. Hope this works and may help if anyone ever has this problem.

 

 

I wouldn't worry to much about a bent pushrod. They are somewhat considered undersized to begin with.

 

Glad to see you’re still with us old friend. That is very strange and I’ve never heard of it.

So you think the lifters were ‘jacked’ from the engine bring upside down with no pushrods/rocker arms?

Did the ‘several bent pushrods’ get bent barring the engine over by hand??

 

The balancer mark at 11 o'clock thing is for piston position in the bore, NOT to bleed down lifters. A guy'd have to be lucky if it were for lifter bleed down (which is INTERNAL TO THE LIFTER ANYWAY) since the cam could be 180 degrees off from the other 11 o'clock crankshaft position.

When the crankshaft is at a certain positions, none of the pistons are at TDC. This allows valvetrain components to be installed without worry of interference when tightening. The position given just happens to be about in line with the camshaft sensor so it's not so arbitrary.

I've got dozens of good used lifters here for a lot of different engines that have been sitting for years...some are still full of oil and have not "bled down" and are hard as a rock.

 

If a lifter plunger happens to be topped-out in its bore, a cam lobe is beginning to lift the lifter, and a piston is within about .070-.090" of TDC (the nominal .060" preload on the lifter - half of plunger travel plus the rocker ratio), there may be interference. I don't have specific numbers so don't hold me to that.

Remember, most diesels have positive deck clearances which means that the pistons stick out above the deck at TDC. The valves are also about flush with the head surface which dictates the timing events are critical as the only clearance between the valves and pistons at certain points can be the thickness of the head gasket.

 

To add to the bleed down scenario, whenever I had to pull the cams on an engine that had bucket followers in the cylinder head, every lifter had to be manually bled back down to remove all the oil or valve damage would occur. Sitting overnight wasn't good enough because the vehicle was tying up a work bay. I had to use a bench vice, place the lifter in the vice horizontally with the oil galley hole pointing straight down. Place a short 3/8 extension in between the the jaw of the vice and the little piston inside of the follower that makes contact with the valve stem and gently force the lifter down to fully collapsed position. Back off the pressure and do that again several times until all the oil was removed from the lifter. Only after doing that could the tech be assured that there would be no bent valves upon engine startup.
So to bring this back to Ford, I think that putting the engine at 11:00 and installing the rockers, then walking away for the evening will yield and engine that will turn over just fine the next morning.

 

I've only cranked on one 7.3L that had lifters that bled down. None of mine that sit for 6 months at a time have any clatter after the first spring start-up.

The one I bought 5 months ago had been sitting for 13 years, cranked unevenly, and it rattled for about 6-7 seconds. It's run like a top ever since and runs better than some others sitting here.

 

So what could have happened that led to bent pushrods in David’s engine?

Lifters not correctly seated over the cam lobes?

Does bent pushrod indicate valve to piston contact??

 

Well I don’t know exactly then what the perfect storm was, I can tell you there is evidence the pushrods that were bent had been bent for more than me just baring the motor over. As you could see signs on the head gasket where they are *** through and slight wear signs on the rod itself. Now when I say bent they weren’t as bad as some I’ve seen, but had a slight bow to them. I am quite confused as to what prevents the lifter from growing to its max extension. And I was pretty quick to install one side of rockers and then bar the motor over before going to the other side. I have pulled rockers for jobs before but never remember trying to spin motor over till after the injectors were installed. And it wasn’t till then that I looked closer and saw the pushrods bent. This truck sat for two years and took only one cycle of the glo plugs and it fired right up. No shake, no hesitation, just drove it right up on the trailer. I really hope it’s nothing to worry about now.

 

What keeps the lifters from full extension?

Valve installed height (dictated by valve seat wear), pushrod length, and deck/head height.

Worn valve seats will cause the plunger to be deeper, head/deck surfacing will cause it to be deeper, and bent pushrods will cause it to be shallower. The valve spring doesn't control the plunger depth but it does dictate how quickly the valve responds due to hydraulics.

 

So I’m guessing just oil pressure keeps the lifter full. But if it somehow gets over full, it has a little check ball that would keep you from being able to bleed them out. I did do one thing a little different this time, I didn’t remove the pushrods, I just left them while I changed the springs. Maybe that oil bled down into the lifters causing just enough “jack” to make contact.

 

Yes, oil pressure vs valvetrain stack-up height (I'll call it that as I don't know the technical term) is what dictates where the plunger rides in the lifter body. I don't know what caused your issue as any number of things could do it.

 

Just to update I replaced the bowed, not really bent pushrods with ones from my motor and got the truck all back together and she runs like a top!