Engine Noise

smurph

smurph

Senior Member
My 1929 engine has developed a disturbing noise which I can best describe as a rattle, or a “clack, clack, clack” (not a clank). The noise usually does not occur at idle, but appears once revs increase (maybe 1500 rpm) and then will usually , but not always, stop as rpm’s increase above 2000(?).
When driving under load there is usually no noise, but when I take my foot off the accelerator the “clack, clack, clack” frequently appears.
I think the problem may be coming from cylinder #2 because when I short out the plugs one by one, I get the expected decrease in revs from #’s 1,
3, and 4 but in addition I hear a definite but more subdued rattle or chatter or clack coming from #2.
Any thoughts about what’s going on would be much appreciated.
Thanks,
smurph
 
You might take a look at the Distributor body and see if it has a crack in it. Also the distance from the rotor to the *** on the distributor body should be 0.025. I have occasionally seen these things warp a bit and one gap will be way too close or too far. Also, you might try a different spark plug in number 2. Ernie in Arizona
 
I think I would try to determine a bit better as to where the noise is coming from. A stethoscope, screwdriver, long dowel, hose, etc can be used. Does it sound louder from top, bottom, left or right ?
 
Thanks for your thoughts. I use MMO regularly in every gas fill up. I have also used a stethoscope which hasn’t helped much. Things sound pretty normal through the stethoscope when the “clacking” isn’t happening.
The noise seems to be a top end noise, about in the middle of the head.
Good idea to change #2 spark plug which I will try. And I’ll closely inspect the distributor body and rotor contact points.
smurph
 
Just to absolutely rule out the generator/alternator/water pump - remove the fan belt. I prefer not to assume anything and like to rule out things even if they do not make sense.
 
I am going to say it likely is NOT valve related simply because you are not describing a miss. If you had a sticking valve or tappet, you would likely hear a backfire or miss in the engine as the valve stuck in the open position. A timing gear noise, -or an oil pump drive noise will not be affected by cancelling cylinders as you described.

I am wondering if you are hearing a piston slap or a loose wrist pin?
 
Easy things first, as EJ suggested I would check the exhaust/intake bolts for proper torque. I believe they are 30ft pounds... A leak in the gasket seal here can really expose some "clatter"... Chap
 
I agree with Brent and I’d go to the drivers side below the water jacket and use a stethoscope. Set your rpm where you hear the noise. Don’t keep driving it thinking the noise will go away.
 
with out hearing it, it is hard to say, but if it changes when you short it out to a faster noise my guess would be a rod. I would pull the pan and check the rod, piston rings wrist pin in that cylinder. Most likely a loose rod.
 
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