Had the following done to my 31 Phaeton engine about 5K miles and 40 years ago: Crankshaft journals, rewelded to standard size, Installed new standard rods, used one thousands plastigage for clearance, (did not "blue-in" fit the rods). Cylinders bored to .20 (however of the 6 pistons, all stamped .20, 3 came from a local individual and 3 pistons from a different suppliers, all cast iron. however, 3 of the pistons were of the tinplated type and measured .002 smaller than the non-tinplated type. Block was bored to piston 'Lock" on 3 thousands clearance as per manual. The 3 smaller pistons were fitted to the rear 3 holes in the block. All new piston rings. Did not weigh the pistons. Reused the original crankshaft bearings they were fine, just removed shims on one bearing at a time until heavy drag on crank. However thrust clearance on Center main bearing was near the upper limit. The cylinder head received new valves and guides at that time, later on new rocker arm shaft, bushings and rocker arm tips reground. Valves have been adjusted many times to .006 and .008, but are still too noisy, with plenty of oil on top. Timing seems to be correct. First issue: When starting and running the engine at lower speed, it feels like the engine is shaking or not running easy and smooth like my all "original engine" in my 31 Spcl Sedan (with aluminum pistons, standard size). Also at idle, there is a low rumble in the engine. sounds like it comes from the harmonic balancer. I replaced tho original balancer since the original had weak and loose springs. Driving on the road at 20 to 40MPH, phaeton engine runs and sounds just like it should (just a little valve noise). Finally, at approximately 1200? RPM the engine has a jay, jay, jay-type knock. The knock appears only at around the 1200? rpm regardless of whether the engine is under load, or coasting, or revved up in neutral. (it could be one of the rods, but putting strain on the engine ( brakes set and try to run) the rods do not knock. Compression is 80 psi on cylinders 1-5 and 70 psi on Number 6. I'll try to attach a sound file at a later date. (Not allowed to upload .mp3 files?)Big question: Should I just keep on driving? COLLAPSE ▲ 0 3
Hello 31Phaeton, Engine rumble and knock. #1 @ low speed: shaking or not running smooth #2 @ idle: low rumble, possibly harmonic balancer #3 @ 1200? RPM knock under load, coasting, or neutral, possibly piston rods #4 @ brakes set and try to run NO rod knock Questions: #1 happens @ low speed means below 1200? RPM and both in neutral and driving? #2 happens @ idle but not above idle? #3 no question #4 with this check-what RPM do you think you get to? Suggestion: Because these deal with sounds, I would secure rear wheels off the ground for running both in gear and neutral and to listen, analyze, and try to pinpoint location of engine sounds at different RPMs. Use mechanics stethoscope. Guesses: #1 Check all spark plugs and wires #2 Listen closely to timing gear area #3 Listen closely along the oil pan length #4 No guess Comment: With 5K miles and 40 years on the engine, maybe it's time to look at all the piston rod connections. As for just keep on driving? I say no.
Have these issues always been there since the rebuild 5k miles ago? Or did they appear more recently? If so, about how long ago? Also, did they all appear at once? Or just sort of accumulate over time?
You've done a good and eloquent job with your description of the issues so far, but without more information I would only be speculating. A short movie clip with good sound would be a huge help. The advantage of a movie over just a sound file is that we get a feel for where you are and where you are moving to with each sound and the way the sound changes. Maybe you could post to YouTube as some have done here and post a link?
Thank you for all the good suggestions. I forgot to mention that I replaced the timing gear with an original fiber one. Parts were easy and reasonable to find 40+ years ago. On the original, the fiber portion was becoming loose from the steel core. Here is the link to my noisy car engine on youtube:
The rumbling noise has been there at least since I installed the current harmonic balancer. The knocking sound you hear at a certain rpm has been there probably around ten years. It has becoming gradually louder over time, but not by much. Maybe it is time to pull the pan and snug up the rods. I may have set the rods a bit loose originally being afraid that they might seize up. Regarding the valve noise, I also installed new springs, maybe the new guides were reamed too tight, but the 5k miles should have loosened up the valve guide clearance....
There is definitely a strange background noise there.
I would think that logically the rumbling is connected to the balancer. Are you sure the balancer is tight on the crankshaft?
As to the knock, I'd have the pan off right away if I were you. The rods on your engine need to be quite tight. If they are loose enough to slide easily on the journal, they are probably too loose. Shims should be removed alternately and evenly from each side of the rod at least until there is a little resistance to movement. In 1931 Chev was saying that if you could tap the rod back and forth with a light tap of a small hammer... they were not too tight. Later, during the 216 era they relaxed that a bit and said as long as you could snap the rod back and forth by hand... they were not too tight.
I think at this point I would check to be sure the rod journal isn't pounded out of round. Hopefully you are okay there
I haven't actually heard that exact rumbly sound you have before. It's a little hard to tell from the video, but it could just be gear noise, although my '29 doesn't sound like that. Hopefully someone who has heard this before will respond. Good Luck!
It would be nice if you could narrow down and identify the location or the cause of the knock. I have used a long screw driver or a stethoscope to locate knocks and bearing noises while the engine is running. You can also remove the ignition wire at the distributor, one at a time, while the engine is running to see if the knock is caused by piston slap or rod problems. Good luck.
