I need some guidance. I replaced my 1979 F100 300 engine with a remanufactured one.
Replaced the engine at my Dad’s. Drove it home and the intake rocker on the sixth cylinder intake came off the push rod by the time I drove it the fifteen miles home. I looked up how to adjust the valves on this forum and found an image with the two adjustment techniques. The only item I could not do was the breakaway torque check. I only have a snap torque wrench and not a gauge torque wrench. I adjusted the rockers until the push rods were tight, plus one turn with the engine cold. The nuts on the rockers loosen up after warming up and valves starting clicking. I redid the same process with the engine hot and the engine ran rough.
Second day I started over with the engine cold and adjusted. The engine ran smooth until I drove it a mile down the road. I assume the nuts must have loosened up again.
Before I start all over I would appreciate some guidance on what I should do. I am considering replacing the nuts on all the rockers with self-locking type. Can anyone provide me with any guidance.
[updated:LAST EDITED ON 25-Apr-02 AT 02:18 AM (EST)]According to my books, and if I remember right, the rocker arm nuts should be the locking type. They look like acorn nuts that have been drilled and tapped all the way thru. The rebuilder may have cheated and provided plain nuts or defective locking nuts. Plain nuts will back off in no time like you describe. Some aftermarket locknuts will have a dent in two or three sides of the nut that deforms the threads. You can always run a jam nut to lock the rockers down if you have enough stud length. Jam nuts can be purchased in a thin profile. But stock type nuts are best. The other problem you may have is that the stock locknuts are just worn out. Either way the people you got the rebuilt engine from should make things right. Don't drive the truck with a rocker and pushrod loose. You could loose a lifter and your oil pressure.
"Beam me up Scotty. There's no intelligent life down here..."
I had this same problem when I bought my '68 with a 240 six in it that someone was supposed to have rebuilt. Turned out that someone installed several different kind of hardware nuts and they had backed off to different degrees. I got the right ones from NAPA. They are 3/8"interference nuts they have a crimped top that makes them look oblong and its best to replace them everytime they are removed.
You also need to keep in mind the adjustment occurs at TDC for each valve. If you don't some will be too loose and some will be too tight. The manuals have a info with a diagram of the crank and how / where to scribe marks so you can adjust each one with the lifter in the right position.
I checked with my engine supplier and they did not have the correct nuts in stock. I checked with a local engine rebuilder and found the 5/16" nuts I needed. The best part was that he didn't even charge me for them! He told me that for 5/16" nuts you torque them to 24 ft-lbs. He also told me that the 3/8" stud nuts you adjust with each cylinder at TOC. I replaced all the nuts and torqued them and the engine runs great. It does sound like one lifter is clicking a little, so I will go back and check them after I put a few miles on the engine.
Sure is nice to have the truck running again. You grow partial to a vehicle after driving it for 22 years. It may not be a new one, but considering I haven't made a payment on it for 19 years what can you say.
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