This started 3 weeks ago. On my '83 Ford F-150, last time I was home I needed to use the truck. It only gets used 1-2 days every 3 weeks. Last time it was pretty cool outside and the truck didn't want to start very well...cranked over a little slower than normal. When it did finally start, it ran very rough (and had to be restarted several times) before it finally warmed up enough to stay running on its own. At this point it started making some pretty loud valvetrain clacking noise and was definately down on power. I didn't have time to investigate then, but assumed the plugs was fuel fouled since I am running on one of the tanks that who knows how old the fuel in it is. Today, I replaced the plugs (not too nasty but definately wet with fuel). It fired right up but the valvetrain noise was even louder than before. I popped the valve covers (no easy feat with 10 miles of dark ages smog equipment, hoses, solenoids, etc). I have 2 bent intake pushrods on the drivers side and 1 bent intake pushrod on the passenger side...and I mean bent BAD. At first I thought I had wiped some lobes since these 3 intake rockers was way loose. The lobes appear to still be fine, but the pushrods are bent to the point that I will probably have to pull the intake off to get them out of there. Why would pushrods just suddenly bend like that? It has never backfired since I've owned it, and before the engine was always smooth and quiet. Maybe the valve guides too tight? But then you would think it would have gotten worse when the engine warmed up to temp...not from a cold start. Any ideas? I hate to just replace them and hope for the best because I have never seen pushrods bend for no reason at all.

Travis..hard to say for sure..but it takes some binding in the valvetrain to bend pushrods.OK..what if valve spring pressure bled down 3 hyd lifters over time.This would have some serious lash clearance now.You start the motor with cold oil and before the lifters can be pumped up..the rockers dance off the valves and the pushrods get flung up off the lifter and collide coming down and bend.I am not real familiar with your Ford valvetrain...just food for thought for you to consider.Hope this helps you.Good luck on your investigation.:beers:

Hmmm...collapsed lifters causing excessive slack in the valvetrain. I can believe that. That would make more sense than about anything else I could think of...although with only 60K miles on it (Jasper long block) that shouldn't be a problem. Other than the pushrods the valvetrain looks great. This thing uses a non adjustable valvetrain...lifter preload is "built" into the pushrod length.

Travis,

You haven't broken some dampers and they are pinching the springs solid have you??

Only thing I can think of off the top of my head.

Dampers do break and cause problems if not caught.

pdq67