Wrist Pin... NOT

[wildcard]

A mechanic says the tapping in my 300 is probably a wrist pin. But he says he would just run it rather than risk messing up something else by going in just to fix that problem.
Does that sound reasonable to anyone else ? And what would be the worst case scenario ?

[70_F100]

Sounds like he's scared of engine work.

Worst case scenario? Throw a rod through the side of the block.

[wildcard]

Thanks. I figured it would be something like that.
Guess I'll get a second opinion and hope he's wrong. After he told me that, I decided he wasn't working on it anyway. I'm not a mechanic, but I'm not stupid either.

[Blue Cloud]

That's what ruined my 390, when I tore down the engine I found the remnents of two wrist pins in the oil pan. I was told it was probably caused by over reving the motor. (possibly because my 16 year old son was smoking the tires)

[wildcard]

Is there a way to tell, without taking the motor apart, if that's the problem ?



'

[fordman]

someone told me a piston knock or slap was a litghter sound than a rod knock. i have never heard piston slap or a bad wrist pin.

[wildcard]

I had a Taurus that had a rod knock. It was more of a thud than a tap.
This sounds like a lifter to me. But then I'm not real familiar with the inside of an engine.

[70_F100]

To find a wrist pin knock, crank the engine and let it idle.

Pull the plug wires, one-by-one.

If you've got a wrist pin loose and knocking, it should quiet down when the plug wire is pulled on the offending cylinder.

[george worley]

I agree with 70 F100 thats how to check for a loose wrist pin. I had that problem with a 352 once and the mechanic told me it was no big deal all 352 Fords do that when they get old just drive it. WRONG!!! two weeks later I started it amd the rod or piston broke and ruined the engine.

[wildcard]

That's pretty much what I was told. He said "those 300s are bullet proof". I'll try the plug wire bit tomorrow.
I really appreciate everyones response.

[DuckRyder]

A wrist pin (or piston skirt/slap, they sound the same) is lighter than a rod knock. It is a distinctive sound if you've ever heard one.

The plug wire trick will also cause a rod to stop, but either way it needs to be fixed and the plug wire trick will isolate the cylinder. Need I mention that you want to use something well insulated to pull the plug wire off....

[wildcard]

OK, I finally got around to doing the plug wire trick. When I went out and started the truck, it sounded louder than usual. So I'm wondering if I want to drive it to work tomorrow. A 100 mile round trip. So I take a piece of 1" PVC pipe about 4' long and put it to #5 plug with the wire on.I suspected that was the one somehow. I could hear a loud tapping. So I go to pull the wire off and felt a small bit of play in the plug. Sure enough it was loose. Tightened it up and restarted the engine and it was almost completely QUIET. Done the same test on the other cylinders and found #4 needed tightening. Now she runs great and quiet.
I really appreciate everyones comments and help.
Also found that the PVC deal is a good way to listen to, and help isolate a noise. Just my So maybe someone can benefit from my mistakes. I know I learned a lesson.

[70_F100]

Good deal!!!

A piece of heater hose will do the same thing.

Either one of them "channels" the sound, and by putting it close to your ear, you eliminate other outside noises.

Glad to know it was something simple. Those 300's are almost bullet-proof, just like an FE!!

By the way, if it were me, I'd go back to that mechanic and let him know what the problem was. Sounds like he needs to sharpen his diagnostic skills!!

[wildcard]

Thanks 70














Thanks 70_F100. Guess I can spend that money on my boat.
I'll definitely let others know about his diagnosing. It's a small town and word travels fast.












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