I have an 87 f150 with 4.9L. I pulled the head and found it was cracked on the 3rd cylinder and both of the push rods were bent. The engine actually ran fine with the head cracked but would act like it was over heating. Well now i bought a used head and put it on. I bought new push rods and put them in. Then i put everything back together. I tried to start the truck and it would not run it would fire off every once in awhile. I never touched the distributor or messed with the timing while it was apart. I moved the distributor some and now the engine runs but not very well. It shakes some and doesn't respond very well. It also sounds like the valves are taping. Thanks for any advice

 

A used head? How used? Did you have it checked out before you installed it? I would run a compression test first then a fuel pressure check then check for codes...might be something as simple as a connector you missed when you put it back together...I do that all the time.

You're a much better mechanic than me if you pulled a head and a couple of rods and didn't mess with the timing...Dare I say just for @#its and giggles that you might might want to do a top dead center check and check the distributor position again?

 

Double check your plug wires. What year is the replacement head? I agree, you should have, at the very least, put a straight edge across the deck surface of the head.