Hammering engine noise - what could it be?

M

Marcus J

Junior Member
I bought a Model A 1930 Fordor last summer and just got it running. The engine is supposed to be restored, but the history of the vehicle is a bit vague. The previous owner is in a retirement home with Alzheimers and the family didn't know much.

The engine runs strong and even, but there is a hammering noise from the engine when the car runs on a level road with no acceleration or deceleration - in cruising mode. As soon as I accelerate or decelerate the noise vanishes. I have a short clip on Youtube. The noise is extra strong at 0:05, 0:13, 0:16, 0:26.

http://www.youtube.com/watch?v=xBpLNBxsloQ&list=HL1373487606

What could it be?

/Marcus
 
I saw one Model A motor where the builder, whoever he was, TOTALLY forgot to adjust the center main bearing. It was adjusted & was perfect. The knocking could be stopped by grounding out #2 & #3 plugs at the same time. Bill W.
 
I'm with James. This is the sound my sedan made, and when we tore it down the mains were in tatters. Pull the engine and take a look. It will only take you a few hours and it will answer all your questions. About the engine, that is.
 
Hi Marcus,

All of the above are good advice; but one thing for sure, hammering will only get far worse with time.


The former owner/pour soul may have been getting forgetful prior to entering the retirement home & this lapse of memory may or may not be directly or indirectly part of the knocking problem.

Get some help & check bearings after oil pan removal.

Wonderful to hear you have a Model A -- best wishes.
 
noises can be tricky. Are you sure it's the motor and not sheet metal or something else loose vibrating in the wind? Does its frequency vary with motor rpm? And, what is the answer to John's question? (thrust bearing concern, I assume).
 
Thanks for all the input. I took it out for a drive tonight. The noise comes on at about 60-70km/h, about 40 mph. At that speed, hearing the noise, I depressed the clutch but stayed with the revs with the throttle, and the noise continued without load. When I applied load, accelerating, the noise went down, but not away. Standing still and revving the engine a little harder than usual - to about the same revs as when driving 40 mph, the hammering noise came again. When it comes on it follows the rpms. So noise above certain rpms and more noise with less load.

/Marcus
 
A loose center main would be my first thought also. My 29 had no babbit left in the center main when I bought the car. The engine would vibrate and rattle at speeds over about 15 MPH, but sounded great at idle.
 
Yup I have heard that before. Advance the timing while idling. You should find that while stationary and at full retard you will not hear very little but once you pull down the advance it will start to make that noise. Center main as others have pointed out is the most likely culprit.
 

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I'm away in Spain for a week but the test with the timing sounds right - I think I got similar effects when driving and making such adjustments. So I guess it's the center main. Thank you all for the great advice! I will return with the final verdict when I split the engine come winter.

Marcus
 
The center main had a 0.0055" tolerance. The bearing looked pretty ok - a lot of material left and in one piece. However, there were no shims, but I filed down the clamp ends slightly so that the vertical tolerance was about 0.002". When running the engine and driving the noise was still there, but a little less prominent, I think. It typically come on when there is no load. All three bearings probably need to be remade/replaced.
/Marcus
 
Marcus J said:
The center main had a 0.0055" tolerance. The bearing looked pretty ok - a lot of material left and in one piece. However, there were no shims, but I filed down the clamp ends slightly so that the vertical tolerance was about 0.002". When running the engine and driving the noise was still there, but a little less prominent, I think. It typically come on when there is no load. All three bearings probably need to be remade/replaced.
/Marcus
Click to expand...

I think it maybe is the bore, there is to big clearence for the piston.. When the piston is i top, and the spark came så will the piston go from " side to side" .. Try to drive with the same idle, and just move the spark advance, is the a difference i the noise..?? Can you hear anything a low idle.??

Per,
 
Where are you living in Gøteborg, ? Or outside Gøteborg,? I am going to Sarpsborg on Sunday and drive tru Gøteborg...

Per,
 
The noise remains, coming on when there is little load applied, above 35mph approximately - when cruising slightly down hill for example, or when revving hard. It goes away when load is applied. There is no big difference when changing the ignition advance. What is more - when I took it up to about 45-50 on a stretch of road and then throttled back, slowing down, there was a much harder banging sound that made me think the engine was about to explode. It didn't, but something is definitely wrong. It seems that it becomes worse when the engine is hotter.

Per - Yes I live in Gothenburg, on Hisingen (Laholmsgatan 16). I'm away on Sunday until early afternoon (Old Style Weekend in Uddevalla). But if you drive past later you are more than welcome to visit.

/Marcus
 
You mentioned working on only the center main. Did you just take a file to it or did you sand the cap on a piece of glass ? Did you check any other bearings ? How did the cylinder walls look ?
 
We used both a fine file and did sanding on a piece of glass. The cylinder walls look ok from the top, but I must confess that I didn't check from below when I had the chance, and we didn't check the other bearings. I will probably take another look next week. Thanks for the concern - I hope to come back with a more comprehensive report soon. I will drive the car some 20 miles this weekend - that may also result in more information.
/Marcus
 
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