Author Topic: Anyone want to venture a guess.  (Read 545 times)

chetbrz

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Anyone want to venture a guess.
« on: August 07, 2018, 08:40:35 PM »

I have a clunk in the engine and was wondering what you guys might think. I have attached a link to a 44MEG image and sound file for your review.  Depending on your internet connection it will take a couple of minutes to download.  Better to download it first then play the video from your download directory.

http://www.1948plymouth.info/1929/images/IMG_1253.MOV

I sent the link to the builder also ?

Chet...

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Articifer Tom

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Re: Anyone want to venture a guess.
« Reply #1 on: August 07, 2018, 10:27:43 PM »
Is it the higher pitch clanking sound every rev or deep clunks , multiples per rev.  . Check fuel pump oil pump .

chetbrz

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Re: Anyone want to venture a guess.
« Reply #2 on: August 08, 2018, 12:33:48 AM »
Tom,

It's the clunk with each revolution of the cam shaft.  It happens twice per revolution of the crank.  Actually once with every movement of the third valve from the left in the video.  Vacuum jumps down from 21 to 19 on the vacuum gauge with each clunk.

I think the valve gaps are too great.  He set them loose (.010 / .012) and I think that causes the cam shaft to transition harder across a single revolution due to the necessary backlash in the timing gears.  Tightening the gap I believe softens the transition across the cam lobe pattern.  You can feel this as you hand crank the motor.  It's like a slight tug left in half a turn then right.  You can feel the crank resist then relax.  PS... No spark plugs in the engine so no compression causing the sound or the resistance. 

I also believe that the lobe pattern of the cam shaft's design is very dependent on this gap setting to smooth out the movement of the cam shaft through one cycle.  When the gap is slightly off due to the setting or wear, possibly expansion from heat (changing the gap) I believe this is what causes the occasional engine sputter.

We will see...
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29plycoop

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Re: Anyone want to venture a guess.
« Reply #3 on: August 08, 2018, 06:43:51 AM »
My first concern is  if the distributor mount is installed you might want to remove it and see if the sound stays the same. They are to hard to come by and is one easy test to try. Good luuck - Rich
Also try checking the valve that isin timme with the noise as it may be sticking up slightly and that would account for for the differance in manifold vaccume. 
« Last Edit: August 08, 2018, 06:51:02 AM by 29plycoop »
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rwollman

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Re: Anyone want to venture a guess.
« Reply #4 on: August 08, 2018, 12:59:41 PM »
Chet_ was wondering if you had any run time on this engine before it went to the rebuilder- If so did u notice any similar noise(s)?

chetbrz

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Re: Anyone want to venture a guess.
« Reply #5 on: August 08, 2018, 02:55:27 PM »
Good questions and suggestions,

Yes the engine ran fine prior to the rebuild except for a knock when driving above 35mph and using/leaking a quart of oil every 50 miles.   Also every now and again the engine would sputter.  A little miss or cough. Not really a problem and I believe it is caused by the home made distributor housing that is installed on my engine.   Functional but now exactly precision. 

Rich, I don't believe the housing is connected to the noise but I do have one on order from Then & Now Auto Parts.  Also I heard the clunk prior to installing my old housing.

I'm going to redo the valve adjustment today before it gets to hot outside.  Between the rain and heat it seems that I have to cut the grass every three days.  Just an extra added attraction to highlight the summer.

To add insult to injury my under ground electric line to my work shop shorted out.  So no power to the work shop.

I think I'll hold off buying any lottery tickets, doesn't seem to be the right time.
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chetbrz

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Re: Anyone want to venture a guess.
« Reply #6 on: August 08, 2018, 06:42:02 PM »

I set all the valve gaps for 0.007 (go) &  0.008 (no go)

It appears like the metallic click is gone ?  See link below:

http://www.1948plymouth.info/1929/images/IMG_1254.MOV

I also removed the starter motor to check the rear of the flywheel for any signs of rubbing.  It checked out OK.

I guess I'll try running it again and see how it goes.  I'll keep you all posted...

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Articifer Tom

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Re: Anyone want to venture a guess.
« Reply #7 on: August 08, 2018, 08:05:00 PM »
Sounds like you got it , Chet . It must have been the valve . That 7-8 is a hot setting , right . So maybe if was 11, back it to 10-9  cold . This is new stuff to me . So I am following close .

chetbrz

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Re: Anyone want to venture a guess.
« Reply #8 on: August 08, 2018, 08:28:12 PM »
Tom,

The Plymouth Instruction Book May, 1929 (page25) states:

Cold Setting for intake & exhaust is 0.008.  Hot setting is 0.006 for exhaust and 0.004 for intake.  The book states that these settings are necessary for quiet valve operation.  I set to 0.007 cold because the valves are stainless steel and may expand at a slightly greater rate than the original carbon steel.  Once the engine is broken in I will recheck and reset the gaps depending on noise level.  The builder set them at 0.010 - 0.012.., he wasn't aware of the 0.006 - 0.004 setting recommendation from the old text.

Maybe fire it up tomorrow, must cut grass again  :(
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rwollman

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Re: Anyone want to venture a guess.
« Reply #9 on: August 08, 2018, 08:43:35 PM »
Chet_ glad u got it worked out - I was thinking towards a binding or broken valve spring as based on your description of the noise in relation to cam revolution.....

chetbrz

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Re: Anyone want to venture a guess.
« Reply #10 on: August 09, 2018, 04:33:26 AM »
Chet_ glad u got it worked out - I was thinking towards a binding or broken valve spring as based on your description of the noise in relation to cam revolution.....

Donít know for sure but we will see when I fire it up again.  Fingers crossed.
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chetbrz

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Re: Anyone want to venture a guess.
« Reply #11 on: August 11, 2018, 08:31:42 PM »
Knock still there.  Maybe a little better ?   :(

Below is a link to a video of the engine running.  Its around 38meg so it will take a couple of minutes to load.

BTW... The noise goes away on acceleration and returns with stable engine speed.  Sounds like a marble bouncing around the crank case ??  I guess I should drop the oil pan and check things out ?  Does anyone think I could have damaged something when the pressure plate got chewed up.  Why disappear on acceleration and return on idle.  Does it sound like valve click to you ?

http://www.1948plymouth.info/1929/images/IMG_3987.MOV

Chet...
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chetbrz

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Re: Anyone want to venture a guess.
« Reply #12 on: August 11, 2018, 11:57:53 PM »
I spoke with the builder and he said lifter noise.

So...

I will redo the gaps.  I am going to go on the tight side just to see if the noise goes away.  Then after a little run time I can recheck them and loosen if needed. 

Its harder working on a rebuilt engine.  With an old engine you don't really worry about breaking it because it is already broken.., that's why you are working on it.  Not the same after a rebuild.  It's like getting a car back from the painter and you are afraid to touch it until it gets its first ding.

As always, let me know what you think,  Chet...
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29plycoop

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Re: Anyone want to venture a guess.
« Reply #13 on: August 12, 2018, 03:16:04 AM »
well one more thing to try. In a rebuilt motor there should not be any ticking noises, sO- It is a little involved but with the symtom you mentioned of a low vacuum at a time. Just a suggestion mind you, remove the intake/exhaust manifold and spark plugs. Bring each cylinder up with both valves closed and blow low pressure in each spark plug hole. If any air leaks from intake or exhaust port on each cylinder that would indicate where you might start a search. If all valves are sealed the same the valves should not be part of the problem. (with all valves adjusted of course) Good luck with your search  -Rich
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chetbrz

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Re: Anyone want to venture a guess.
« Reply #14 on: August 12, 2018, 05:34:32 PM »
Thanks Rich for the info.

After the last gap settings the engine ran very smooth except for the knocking.  To eliminate all problems with the gap setting I tightened the gaps again today which didn't affect the clunking.   At this point I am convinced the sound is coming from the rear of the crankcase.   Maybe something broke when the engine chewed up the pressure plate.  I am dropping the oil pan to get a look see.

I used a long screwdriver to listen to the block vibrations.  Starter motor bell housing OK, Distributor base OK, even the area around the tappets was soft.  No bangs coming from the oil pump.  Sound definitely coming from the rear and below the valves.

Manny thanks for your suggestion,  Chet...
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