Noise under load

J

jerrytocci

Senior Member
Hi folks, I am getting a noise from the engine or somewhere else, this only happens when I accelerate and when the car is moving. Any ideas?
 
There are a couple of things that can be happening. If the ignition is too far advanced you may be hearing a knocking. First thing to try is to slightly retard the ignition and see it that helps. Have you searched for the knee in the advance curve? Do you adjust your timing depending on the driving conditions?

The second thing is a loose main bearing. This will cause a deep knock under load. The only way to check is to take the caps off the mains and check the clearance. This is best done with the engine out of the car and up side down on an engine stand.
 
My mind goes to losing a rod-nut while traveling the Mid-Cape Highway (at 50mph) back in the 1980s.

Whappa-whappa-whappa.

Pulled over to the side. There was definitely a "threshold" below which the engine would run but going up in speed/power the whappa returned.

Following the "service road" back to an exit, I made my way at less than 30mph back to my house.

A tear down found the loose nut in the bottom of the sump (NOT in the dipper tray)

Understand that the engine was SEVERELY worn with egg-shaped journals, filed caps, and setting it up to run by pushing it to that "just binding" point on the eggs. Apparently setting it up for just enough vibration to loosen the nut, break the cotter, and the nut backed off.

Young and stupid in those days. Not so young anymore.

Joe K
 
I think any serious tear down engine work is best done engine with engine out of car and on stand. but as for main bearings on the Model A engine, can be done quite easy with pan off and engine in car. (disc batt +) i scraped in a center main with engine still in the car...

then the low speed, 'under load' noise was gone! :)
 
What about jackstands, and start the car, put it in low gear then get out and find the noise with a long screwdriver to the ear (stethescope)?
 
I tried to isolate an under hood noise using a very long wrench pressed to my ear. Turns out the spark can jump from a high tension lead even without touching it! This electrical impulse traveled up the wrench and directly into my ear.
Besides jumping back pretty quickly from the jolt, I do not seem to have suffered any long term damage. I was hoping to, at least, improve my fading memory or even receive AM radio broadcasts without a radio, but got nothing except a funny story.
 
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