Engine knock (oh no,)

M

MikeMort

Junior Member
Hi fellow A owners, new guy in town doing his first post on this forum. Found the A of my childhood dreams (1930 Tudor) and brought it back to life after more than fourty years of silence. Did everything myself, including painting and even sewed up a new interior myself as wife refused (had never used a sewing machine before, but there is a first time for everything). Cleaned and Assembled engine myself lying on my knees. Ended up with a very nice car, certainly not a showroom restoration but as I see it an original and very authentic looking car, a real pleasure to drive, and lots of fun for the family on weekend trips.
Now to something that worries me:
I have a knock coming from somewhere inside my engine lower half (oh no! I hear you saying). It is only there when engine idles at its very lowest speed, both levers fully up, sounds like someone is gently beating a metal pan with a spoon. As soon as I bring down ignition lever some, or open the throttle, or both, said sound disappears. Hope it is not my bearings, I run 95 octane fuel aand ignition is just a tiny bit too retarded. Any hints welcome.
 
When you say you cleaned and assembled the engine, did you disassemble it completely or just enough to make it look good? I find, when a motor sits for lots of years, the oil in the main bearing tubes has a tendency to solidify and block them. I also find, old oil will etch the crank and cause damage to the bearings when left to sit for only a couple of years sometimes less. The best way to prevent this is to remove the crank and clean the tubes before trying to start any motor that has sat for many years. Your location might prompt someone close by to come give it a listen.
 
I dismantled the engine down to its smallest bits, until I held the cranckshaft in my hands, gave it new piston rings and valves. Of course I took great care to arrange shims on rods and main bearings in the order that I found them. Runs good, I have done about one thousand miles and almost no oil leaks (must have been beginners luck).
 
It could be a spark knock, since it goes away when you advance the spark. Check that you've got it timed properly. Run 87 octane.
 
iI wonder if it could be the cam walking from a weak or missing spring ,, or,, a loose/worn timing gear..
 
Mike,

Because of hollow metal parts all tightly fastened together, encasing moving parts, many times we hear sounds & "think" we know where they originate.


Maybe you have verified exactly "where" this knocking has originated; others do not always do this.

Anyway in trying to asssit others in resolving problems, this is my rural minded humble opinion on why every Model A owner/mechanic should have an "inexpensive" mechanic's stethoscope for trying to pinpoint engine "noises".

Serious 1800's doctors acquired the "new" stethescope device whereby they could pinpoint internal heart ailments, lung disorders, etc. without opening the patient's chest cavity; however, many "old fashion" doctors decided to save money & continue externally observing their patients & try "hit & miss" medicines for years.

Here we are in 2012 where it is amazing to see how many "old fashion" doctors we still have tearing things apart & re-assembling only to find the noise came from something as simple as a crankshaft pulley. On Amazon.com a $!2.50 stethoscope could have saved countless hours & misery. Kinda like a Winn-Dixie grocery store card, wouldn't leave home without it.

If it is defiinitely a spoon hitting a pan sound "in" an oil pan, time to drop the pan to investigate.

Hope this helps.
 
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Good suggestion from H.L. A two- or three-foot 3/4" dowel, or a length of old broomstick, will work like a stethoscope too.
 
Hard to say , I assume it goes away under load also.All the big hitters ( rods bearings ,mains bearings,valves,cam,piston pins) will normally get louder under load ,not go away.As suggested,get a stythescope,broom handle,screw drive ,put up against the engine at various locations .Probably would not hurt to take out the plug under the manifolds and see if any oil come out.
 
As James stated,spark knock is caused by the timing being advanced to far .I am currently working this spark knock ( rattling ) problem and have just about got it quited down after putting in a new distributor and used the nuex wrench on the dist. cam.The old dist .had so much play in it you were basically guessing every time you time it. I posted my problem here about 2 weeks ago.
 
When you say that you took great care to arrange shims on rods and main bearing in the order that you found them did you use some platigauge to check what the tolerances were. You might need to tighten things up a bit.
Dave

MikeMort said:
I dismantled the engine down to its smallest bits, until I held the cranckshaft in my hands, gave it new piston rings and valves. Of course I took great care to arrange shims on rods and main bearings in the order that I found them. Runs good, I have done about one thousand miles and almost no oil leaks (must have been beginners luck).
Click to expand...
 
Duffy1 said:
As James stated,spark knock is caused by the timing being advanced to far .I am currently working this spark knock ( rattling ) problem and have just about got it quited down after putting in a new distributor and used the nuex wrench on the dist. cam.The old dist .had so much play in it you were basically guessing every time you time it. I posted my problem here about 2 weeks ago.
Click to expand...
2 things that might help, use high octane gas and rebuild the distributor drive to help eliminate play in the system.
 
Thanks . When at a stand still and the spark advanced about 3/4 the way down no problem at idle our when you rev the engine up . If I put the spark all the way down at idle no problem .When I rev it up you can hear a slight raddle but nothing like it was 2 weeks ago.I may try and retart the timing a little and see what happens although it is really running smooth and strong as it is.
 
This may be too far out for any expienced Model A owner, but here it comes: would it be possible that the end of a conrod can actually hit the splash pan? Thanks all of you for your help,
 
Mike,

After a few years of experience, one learns that "Anything" can happen with a Model A owner/mechanic -- just suppose the splash pan popped up & the connecting rod is the spoon you report hitting on the pan -- who knows? If noise is in oil pan, the oil pan should be removed.

Hope this helps.
 
MikeMort said:
This may be too far out for any expienced Model A owner, but here it comes: would it be possible that the end of a conrod can actually hit the splash pan? Thanks all of you for your help,
Click to expand...

I don't know how it could, but if the dipper tray isn't snapped into place completely it might hit that?:confused:
 
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