MikeF62

Hi, I'm new to this forum so please bear with me. I have a restored numbers matching 1966 427/425 which I recently took in to a mechanic, who I really trust, for some minor work, valve lash, tune-up, oil change, etc.. During this work, he found an issue which he suspects is a bad wrist pin but has been unable to verify. We've tried to remove plug wires to isolate the problem under load which did not make any difference. What is bothering me is that it is a clattering kind of sound which does not occur until the engine is running around 2000rpm. Does anyone have any experience or suggestions in how to determine what is causing the problem. I want to avoid another rebuild if possible and want to make sure that it is a wrist pin before I start an expensive tear down. Thanks, in advance, for any help/suggestions or insights you may have.

Critter1

Welcome to the board.

Highly unlikely it's a wrist pin. It is common for solid lifter big blocks to have piston noise though. If so, it would also be heard at idle too.

Easy Rhino

Can you relate why the mechanic thinks it's a wrist pin?

Also, clarify the pulling the spark plug wires test.

plaidside

A bad wrist pin will have a 'double' knock and normally the sound will change when the spark to that cylinder is removed.
Did it make this noise before you brought the car to your mechanic? Did it develop after he worked on it?
Some possible causes could be the fuel pump, something on top of the piston, loose flywheel bolts, loose harmonic balancer or cracked or loose lower pulley.
Joe

63split63

Could be a loose flywheel cover .

DansYellow66

Long shot but do you by chance have a Centerforce clutch? I've read some posts suggesting they could hear clatter from the weights on the fingers. I ran one for about 1,000 miles and never heard anything from it but then my hearing is far from perfect and my car has 2-1/2 inch sidepipes.

MikeF62

Thanks for all the input/suggestions. Let me try and respond to all the questions

The sound it makes is more like a clattering sound, not a knocking. It starts around 1700-1800rpm.
I didn't hear it before I brought it in but with the side pipes that doesn't surprise me
I don't have a "Centerforce clutch"

UPDATE: Got a call from my mechanic who said he found the problem. Went down to his garage...he pulled the pan and used a borescope on it this morning. Found a bad piston... so it looks like its going to be an expensive summer...bummer!

Thanks for all the suggestions and ideas

Factoid

Crunch527

I'm with the "loose fly wheel cover"...

MikeF62

Yeah, it wasn't something I wanted to hear, but its the nature of the beast that we all love...sigh

Here are some pics



At a recent car show


Me and the Beast

Critter1

I wonder how he could tell that it was a bad piston seeing it from the bottom? Unless a chunk of the skirt was broken off or maybe when the piston is at BDC the side if the skirt is visible?

L78racer

could be a bad fuel pump.

MikeF62

He went in with a bore scope first, then pulled the head to verify. Now hopefully the stars will align with the machine shop and I'll get my "Baby" back before the end of the show season...

20round

I AGREE! SOMETHING DOES NOT SOUND RIGHT? no pun intended..maybe you should get a second opinion...JMTC...troy

DansYellow66

Did he pull the pan? Maybe he drained the oil and went in through the drain hole with the camera wand but not too likely unless the windage tray is missing. Not sure how he could tell anything about a piston skirt from top side.

plaidside

I would love to see a picture of that piston.
Joe

Tig65gs

MikeF62

Once he's pulled the engine, I will take some pictures with my camera of what he finds and post them. I know he can save pictures on the bore scope, not sure if he can print them from the scope.

Randy G.

Post #7.

DansYellow66

I asked the question in post #6.