The noise completely goes away after driving a couple miles. So it can’t be the heads or anything above the pistons. Today I listened everywhere from above and below with an engine stethoscope and no knocking sound anywhere. The engine sounded totally healthy. Mysterious…
The aluminum pistons expand the most when hot compared to the cast iron block, so I would agree with another commenter that it is either piston slap or a worn wrist pin. Is the oil pressure ok? If this was rod knock from an excessively worn bearing that clearance would allow a lot of oil to leak by and reduce the pressure. Plus warmer oil is thinner which should make a rod knock worse on a warm engine versus a cold one. Otherwise beautiful car!
I thought of this too since he says it quiets down when it warms up. Usually a spun bearing or cracked crank get louder when things heat up. Some 50s engines used cast iron pistons... I don't know about those Mercurys though.
You can get a cheap stethescope at Harbor Freight. Had a couple fuel pumps that did that I was sure the engine was bad Id dump the oil and get the pan in the sun see if you find any glitter.
If it gets better when warmed, I’d lay my money on piston to cylinder wall clearance being to great. If when warmed it gets worse it’s time to do something about it! I think your piston to cyl wall clearance was .002
Beautiful car !
That's definitely a rod knock of some type or an if somebody dropped a bolt down the carburetor immediately shut it off and get a borescope.
The noise completely goes away after driving a couple miles. So it can’t be the heads or anything above the pistons. Today I listened everywhere from above and below with an engine stethoscope and no knocking sound anywhere. The engine sounded totally healthy. Mysterious…
Always check the simple stuff first like a fuel pump clunkin, or a torque converter not properly tightened,, loose flywheel,,, you may get lucky....
I like this optimism!
@@brianp6965 Hey,, a man can dream !! lol
Machinist in a journeyman that's definitely a rod knock somebody dropped a small 🔩 bolt down the carburetor something.
Use a mechanics stethoscope to pin point the noise area. They really work.
STP always works for me! 🏁
The aluminum pistons expand the most when hot compared to the cast iron block, so I would agree with another commenter that it is either piston slap or a worn wrist pin. Is the oil pressure ok? If this was rod knock from an excessively worn bearing that clearance would allow a lot of oil to leak by and reduce the pressure. Plus warmer oil is thinner which should make a rod knock worse on a warm engine versus a cold one. Otherwise beautiful car!
Sounds more like piston slap
I agree Mike. Especially if the pistons are the heavy factory slugs. I say, leave it alone and enjoy the car. If there’s a problem, it’ll get worse.
I thought of this too since he says it quiets down when it warms up. Usually a spun bearing or cracked crank get louder when things heat up. Some 50s engines used cast iron pistons... I don't know about those Mercurys though.
Yup.
Yep gudgeon knock, it’s fine
You can get a cheap stethescope at Harbor Freight. Had a couple fuel pumps that did that I was sure the engine was bad
Id dump the oil and get the pan in the sun see if you find any glitter.
If it gets better when warmed, I’d lay my money on piston to cylinder wall clearance being to great. If when warmed it gets worse it’s time to do something about it!
I think your piston to cyl wall clearance was .002