Hello all,
I have a 71 f100 sport custom...360, 4 speed granny, 85 k miles.

I just bought the truck last year and it runs pretty good but I am trying to get it running perfectly.

Lately I've noticed a "tapping" sound coming from the engine. Someone told me it was the valves and someone else told me it was a "lifter that needs asjusted" which I haven't a clue as to what that means nor how to do it.

My questions. What do you think the sound is and how hard is it to adjust a lifter and how important is it?


andrew

 

We need more info to help you. Is this primarily at idle? Does it get louder and softer? Does engine temp have an effect on it, like worse when warm? Does it happen when you mash the gas?

-Scouder

 

I hear it at idle and it speeds up as the truck accelerates and then remains constant when the truck is cruising. Does not seem to make an appreciable difference if the truck is warm or cold.

Mashing on the gas and accelerating seems to make it louder and faster.Truck runs very smooth otherwise but is hard starting cold.

 

stuck lifter maybe?

 

If you can tell what side the sound is coming from, pull the valve cover, then rock the rocker arms on the valves that are closed. turn the engine, by hand until you get to them all. If you find one with any play in it, that should be the one making the noise. Check the push rod to see if it is bent. If it is the lifter that is stuck, you will need to replace. Also check the rocker arm shaft for wear at the nosy one.

 

It is likely that you have hydraulic lifters, and non-adjustable rockers. So you can't adjust anything. It could be a bad lifter, or it could just be the normal tapping associated with the valvetrain. Unfortunately, it can be difficult to diagnose. For example, from what you say, there really isn't any change with temperature, but most problems that make tapping, from lifters to piston slap, will be affected to some extent from cold to hot. It might be worth your time to take it to a reputable shop and have them give you their opinion.

-Scouder

 

I'm thinking wrist pin.

 

Just to further muddy the waters, what about an exhaust leak? Nothing temp sensitive about that and I've heard 'em sound just like a tappet. The tell tale is black residue at an exhaust joint somewhere. Sometimes you can feel it with your hand too. Just don't get burnt!

 

An exhaust leak is not so much of a tapping sound. I had this same issue and the truck was performing poorly, so I took it apart and it had a piston (#7 to be exact) with some huge chunks taken out of it, I haven't had time to take a good look at the valvetrain yet, but I'll put money on it that a valve struck that piston. I'd get those heads off ASAP and take a look at your valves and your pistons. How many miles are on the motor?