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John_Mc

Is this noise a wrist pin???

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Please listen with the volume up.  Any input would be greatly appreciated.  I've been told on high authority, Tom O'Donnell,  that this is at least on wrist pin and before I take the steps to remove and rebuild this engine, I'd like confirmation.

 

This car has 61,000 miles and paperwork indicates is was totally rebuilt, some 30 years ago, with 59,000 miles.  The car starts instantly and idles beautifully.  Uses no oil and only begins on a hot motor and roughly 1,000 rpm's.  I'm using 20W/50.

 

Any advice????  Thanks in advance

 

https://www.youtube.com/watch?v=jLw0XDYyTNE

 

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Seems to me a loose wrist pin would make noise from the get-go?  This may be a "sticking" valve as that condition is RPM sensitive. When you drive the car do you notice any small difference in power when this noise starts to occur?

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Peecher, thank you for responding. 

 

No, there is no power differential when the rapping noise starts, but your point is well taken.  Would not a loose pin make noise at all temperatures as well??  This loud rapping noise takes place ONLY under 2 conditions:  1) higher rpm's and 2) a hot engine.

 

I can't think of what inside that engine would cause such a ruckus under those two conditions and I really don't want to rebuild this motor if I don't have to do so.  If I did not mention it earlier, this car starts on a dime and idles beautifully. 

 

Thanks again, ideas from those far more knowledgeable than me are welcome.

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Here's something you can try: with the engine running while making noise, start shorting the spark plugs one at a time. If the noise lessens/disappears this will isolate the source of the noise to a cylinder/piston. May have to remove the cylinder head for a look-see before going any further.

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Hi John.  A couple of years ago I had a similar noise in a very tired '41 engine.  I kept driving it which was a mistake because the engine was probably rebuildable.  Here's a couple of photos of what I found after pulling the engine and opening it up.

If I had to do it over again I would pull the engine earlier.

Mike L.

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post-118378-0-24953600-1435596575_thumb.

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Thanks once again.  Tom and I did that and the noise remained the same after shorting out each one of the cylinders one at a time. 

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Hi John.  A couple of years ago I had a similar noise in a very tired '41 engine.  I kept driving it which was a mistake because the engine was probably rebuildable.  Here's a couple of photos of what I found after pulling the engine and opening it up.

If I had to do it over again I would pull the engine earlier.

Mike L.

OMG, that's awful!  I'm very concerned and that's why I have to get tot he bottom of the problem.  If I have to rebuild the engine, then that's what I do but it sure would be great to determine the root issue.  Did you find out what caused such destruction??

Edited by John_Mc (see edit history)

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OMG, that's awful!  I'm very concerned and that's why I have to get tot he bottom of the problem.  If I have to rebuild the engine, then that's what I do but it sure would be great to determine the root issue.  Did you find out what caused such destruction??

I would say the wrist pin let go.  You can see the broken connecting rod in my first picture.

Mike L.

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Mike, one last question, was this engine making a noise similar to what I am describing before it let loose?  If not, did you get any warnings??

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Another thought: You might check and see if noise is coming from one of the water pumps. You can either listen thru a piece of hose held close to block near the pump(s) or disconnect the fan belt. This will eliminate the generator as a possible cause also. Dee

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Hi, we did this also and checked out other possibilities such as the fuel pump, generator etc.  I do not think it is coming from the front of the engine, but rather the back.  Thanks.

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This is probably nonsense but perhaps the oil pan baffle may have come loose? it just snaps in but is usually very snug. Windage from the spinning crankshaft might be causing it to contact/make noise?  

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Never thought of that but I dropped the pan several months ago and the tray was very tight although possible.  Good thought though and I thank you for it, but I don't think a loose tray would not be affected by temperature.

 

This Thursday I'll be taking it to another highly knowledgeable shop owner who will give it a listen.  This is a friend of Tom O'Donnell's and I report what he says. 

Edited by John_Mc (see edit history)

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Did you check vacuum? fluctuating could indicate bad valve.  I've "fixed" similar noise in flathead 6 with a can of STP.  Ran for quite a while after. 

Abe

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Mike, one last question, was this engine making a noise similar to what I am describing before it let loose?  If not, did you get any warnings??

Hi John.

The sound was similar to what I hear in your video clip.  It got louder the longer I drove the car until ultimately the rod separated from the piston and punched a hole in the cylinder wall.  I should have known better.

Mike L.

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Mike,

You are a good man to admit that and im going to have to watch it carefully, especially since the noise sounds the same!

Thanks again.

If i have to pull the motor, its really OK, just want to know where im starting from.

Edited by John_Mc (see edit history)

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Its anyones guess, see if you can figure which side, top or bottom of the motor the noise is coming from then I would remove valley cover, and check for broken valve spring or piece of guide encaged in spring bouncing around or broken horse shoe retainer allowing guide to float about. Could be top off piston or loose rod bearing. I wouldnt run it too much more before opening it up.

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Excellent advice, did not realize I could see so much of the engine with the valley pan removed. I'm taking it tomorrow to a flathead expert here and then go from there. I think pulling the engine would be a good learning yet expensive experience.

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John,

 

Pulling the engine is not expensive, it's fixing what you find when you disassemble it.

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Very true, im bringing it to Mike tomorrow and ill let you know what he says.

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Im betting my dollar on a lifter. The noise dont sound heavy enough to me for a  rod bearing or wrist pin. I would pull the intake and check for a loose valve first. Your car being a 37 it doesnt have hydraulic lifters but it may have adjustable lifters.

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Took another look at your video. It looks like the cylinder heads are cast iron and you may indeed have an engine that is newer than a '37. That sound coupled with the low oil pressure and warmed up engine could very well be a hydraulic valve lifter(s). You can tell if you have a newer engine by checking the exit routing from the oil filter...late '38 and newer engines exit line from the bottom of the filter canister are plumbed into the lower port at the left rear of the cylinder block. All V-12s(except '36)will bolt right into your car. Something to check anyhow. a noisy tappet, by itself, won't to any harm.

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Good point Peecher. If that engine is indeed a later engine with hydraulic lifters I would consider changing the oil from the heavy weight thats in there to a much lighter weight. My thinking on that is that maybe there is a lifter thats starving for oil and the thinner oil may flush out a piece of trash.

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Thanks guys, I took the car to a local expert flathead machinist who thought it was either a lifter or broken valve spring. His suggestion was to remove the intake and valley pan and have a look which I will do in a few weeks.

All of you suggestions have bee great and really appreciated.

Edited by John_Mc (see edit history)

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After reading my original post, I realized I never revealed the problem.  I was a loose wristpin and because the motor was to worn out I'm replacing the engine.  Thanks for all the input!

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