Engine "Rattle"

daveymc29

daveymc29

Well-known member
I have a rattling sound when I reach about the shifting points as I accelerate. It is heard more on the right side of the engine. My hearing isn't 100% so I have had friends listen and I have used a stethoscope and can't pin point it. It is not heavy enough for a rod or main, or so all my friends say. I pulled the pan and cleaned the sludge, no rabbit signs and the rods slide a bit fore and aft, but no real looseness, it seems to me.
The cam had the ends of the teeth (about 8 of them) broken off. Replaced that and adjusted the valves to .015 and .013, go no go. Once years back I changed the fibre gear because all the teeth had broken off about 1/8th of the tips. No rattle at that time. All springs and keepers look good. Put it back together and fired it up, rattle still there at same rpm range, nothing changed. (Fan belt removed during tests.)
Any suggestions welcome?
Daveymc29
 
You're lucky no rabbits were found in the pan, or you'd really have problems. :D

Is this a constant rattle, any time the engine is running, even at idle?
Have you pinned it down to being on the engine?
Have you used a stethoscope? Still can be tricky though, as the sound can easily travel to the other end of center of the block.
Do you have engine side pans, that may be rattling?
 
This rattle is there if I accelerate moderately hard, but will show up with no load if I run the rpm up while sitting in neutral. I can shift just a bit before it wants to start the rattle and then it goes on fine. I can't hear it at road speed, but that is not to say its not there. I usually just keep it under the rattle rpm around town. I found it by accelerating the engine at a stop sign to activate the alternator. It will always come on, I'm guessing at about 15-1800 rpm and continue as I go to the limit. Not at all like i'd expect of a bearing.
 
This may sound dumb, but check the tightness of the radiator support rod nuts, especially at the firewall. Looseness in the rods sets up a harmonic rattle that can be confused with engine noise at certain RPMs. The firewall acts as a telegraphic path for the noise. It's confounded some of the best Model A mechanics over the years.
Marshall
 
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Marshall brought up a good point, and also reminded me that if you have the hood catches (to hold the open hood), I've seen them rattle also.
 
I had a rattle coming from my engine too,turned out the bearing on my fan pully was worn and it would hit the radiator at high engine rpm. I caught it in time and replaced the fan,and water pump..
 
At the Suggestion of Bill Williamson I got one of these... it might help you....

http://www.harborfreight.com/mechanics-stethoscope-69913.html

image_22652.png
 
This rattle, if you don't mind me calling it that, is there at the middle to high rpm's. I have the hood and radiator off the car, just enough on it to run the engine for a half minute or so. It still rattles when I rev it up. Not a knock that I have heard before, more of a rattling sound and it appears to several of us to emanate from the valve side of the block. No accessories are on the engine yet, water pump, Alt. etc.
 
Also, no engine side pans, no hood rods, no rabbits, Also no Babbitt in the oil pan, used the stethoscope, clutch in, clutch out. I'm stumped at this point.
 
I would suspect something in the camshaft/distributor area. I've had a similar rattle in my roadster and it seems to come from the manifold side of the engine. My rattle goes away under slight acceleration. I've had the engine apart except for the cam and haven't found anything, aggravating isn't it. I run mine and don't worry about it.
 
Just about to pull the pan again and verify that a rod isn't too loose. It seems to now be a bit louder than a few days ago, or I may be hearing better. I have asked a Model A guy with better ears to come listen to it on Monday. So, I won't pull much apart until a guy or two have listened.
Thanks for all the above thoughts. Feels good to have a resource for more thought when I reach a mental impasse.
 
Marshall mentioned the radiator support rod nuts. I have learned that a buzz/rattle in the firewall can REALLY sound like it is coming from inside the engine. Like Marshall mentioned, mine turned out to be the support rods.

Two things I would recommend, first walk around and thump on the firewall and other panels. See if you can reproduce the sound.

Second, while you are driving and you get that rattle, have a passenger press hard in different places on the firewall, and other panels to see if you can dampen the rattle. Also, check things like the GAV rod, speedometer cable, and things going in and out of the wiring tunnel under the gas tank.

Good luck.

Ken
 
Long shot but I had a valve seat come loose and cause the same issue. Intake on #3 looked fine when we pulled the head, but when digging deeper it fell on the floor.
 
Is it nice and quiet like mine is when idling or low throttle or just in the midrange of RPM?
Is it louder as the engine warms up? Curious to know the culprit.
 
These noises can be frustratingly difficult to pinpoint. I too have a similar rattle and have checked some pretty unlikely things but it still annoys the Cr@p out of me. I even considered that the rods might be moving along the bigend journals and making a noise when they hit the end.
I've reached the point where I say "let it go - if it gets worse, it'll be easier to find. If it doesn't, it doesn't matter".
 
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