I have an 82 F250 with the 6.6L engine. The truck was given to me, and i have been tinkering with it in my free time. After a little diagnosis with a vac. guage and compression tester i discovered my #5 cylinder was basicly dead. After pulling the valve cover i found that the rod on the intake valve for that cylinder was badly bent. I know my way around an engine, but this is the first repair of this type that I have done. My first question...is it as simple as replacing the rod and putting it all back togeaher, or is a bent rod a symptom of a bigger problem? What can cause a rod to bend like this. I checked, and the valve does open when pressure is applied to it. Second, after looking through the cylinder head with a flashlight it appears as though the lifter is not in the hole where it belongs. I suppose i'll have to pull the intake manifold to check and see if it's rolling around in there. Third, i'm not sure how long the engine has been like this. Is there mechanical damage that can be caused by running an engine with a dead cylinder (because the intake valve is never opening). I would think that it would still get lubricated, so i'm hoping not. Any tips or suggestions for this type of a repair would be great! Thanks for the help in advance.

 

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There are a lot more knowledgeable people on here than me, but its possible its something as simple as a bad lifter. Whatever you do, I'd recommend not reusing the old lifter. In addiiton, I wouldn't even think about putting it together again without first trying to check and make sure the cam lobe is OK. If you remove the intake manifold as you suggested, and remove the lifter, you should be able to shine a flashlight down the lifter bore and check the lobe.

Find the old lifter and see if it still compresses, or if it has locked up. I'm keeping my fingers crossed that its just a bad lifter.

 

I personally know a person who would do things like this to fix a bad cylinder, this could be a similar bandaide. I can't imagine a lifter just popping out, 90% of the time, they are trouble to remove from buildup at their base, took twisting and vicegrips to remove mine, and my engine was a high miler.

 

Well, at this point i'm not totally sure the lifter is not there...i had bad lighting where i was working and my flashlight died. I just couldn't see it in there. I'm more concerned with what bent the rod itself. I guess it could have bent after it came loose, but what would cause that to happen? Could a bad backfire cause anything like this? When i first got it running, it ran REALLY bad, and was backfiring quite a bit at first. Luckily the parts are super cheap at NAPA, so i'll go ahead and replace the lifter and the rod. The most expensive part is the intake gasket...lol

 

The pushrod could have slipped off the rocker for a number of reasons. One of those is a collapsed lifter, another is excessive clearance in the valve train. Lack of sufficent oil to the lifter is a possibility. The valve train for cylinder #5 is the last to get oil. If someone drove it low on oil, that could happen.

Replace the lifter and pushrod, then listen for valve train noise, and check the oil pressure at idle when warm.

 

**UPDATE** OK, yesterday I pulled the whole thing apart. Got the intake manifold off, found the lifter still in the boar where it belongs. It didn't look bad, but I replaced it anyway. New pushrod went in without a problem. Replaced the manifold gasket, both valve cover gaskets, put the whole thing back togeather and started it up. runs ok, but i think there is still a problem. The engine is MUCH smoother than it was before. After it was warmed up, i put the vac guage back on and was very disapointed to see a reading of 10! Now, i realise that indicates low compression..but before i pulled everything apart the vac guage was reading almost 20, and would drop to 15 every time the cylinder with the bad pushrod was supposed to fire. I'm thinking that i may have a vac leak at the intake manifold. I spreayed all along the edges with WD40 to try and locate a leak, but couldn't find one. Is there a trick to installing it, because it's a big pain the butt to do it yourself. Thing is heavy, and the gasket kits are almost $35 each (and can't be reused). any suggestions on this would be great. Let me know what you guys think!

 

Well, to begin with, you really need to find out why that pushrod bent. They don't just bend by themselves - there has to be an underlying problem (cam lobe, valve spring, etc). Could you confirm if the lifter was just shot? If so, then thats a good thing, because it could have just been a bad lifter.

As for the vacuum: time to start looking for vacuum leaks. That means spraying around intake manifold gaskets, vacuum connections at manifold, etc. Also, look for vacuum lines that may have been disconnected.

 

Well, the old lifter looked ok...i didn't really test it or anything. The cam lobe looked ok from what i could see through the lifter boar. I ran it for about 25 minutes yesterday, and it wasn't makeing any valve noise, and ran smoothly. I'm not really sure what caused it to bend, but that cylinder has good compression now, as do all the others. I'm guessing there is a leak between the manifold and the heads, but i'll double check for vac lines on Wed. I really hope i don't have to pull the intake again....once was enough!

 

Pull the valve cover on the side of cylinder #5 and check the operation of the valves on that cylinder. You can do that by first pulling the coil wire and have someone crank the motor while you watch. Also check the plug and wires for that cylinder.

 

I did that before i put the valve cover back on...cranked it over quite a few times...everything looked like it was working properly after i replaced the bent rod. The cylinder is working again as well...just a low vac problem now.

 

a vacuum of 20 at idle is good. Bouncing vacuum readings can indicate bad valves. You need to do a leakdown test to determine if the valves are OK.

 

Well, compression checks good on all cylinders. Vac needle is no longer bouncing around. it's steady at 10. Before it was bouncing between 19 and 15 (before i fixed the rod). The reading is now steady, but low.

 

What carb and intake do you have?

Did you torque the intake?

What pattern did you use to torque the intake?

Did you use a valley pan or just gaskets?

Did you check the carb for vacuum leaks at the base and the fittings?

 

You had the intake off, go back and retorque everything. When I swapped out my intake it leaked like a sive until I retorqued everything.