swiggy
----------
- Joined
- Jan 13, 2011
- Location
- Victoria, BC
So I have a strange rattling sort of noise whenever the revs drop back down to idle. So for example you rev the engine in neutral, as it drops back down to 900 rpm or so this rattling will start, it sounds like something 'spinning down', almost like a small ball bearing rolling around something. It sounds metallic but definitely doesnt sound like the motors about to explode. It has done this without any change for at least 5000 kms, hasnt got any worse. Sometimes it will continue to rattle at idle, sometimes it will stop. Motor runs great, super smooth for a carbed car with 460 000 kms.
I thought it was the dizzy, but after swapping to electronic ignition from the points there was no change. Louder on the intake manifold side, Ive tried using a vacuum tube as a stethoscope but no real joy, hard to isolate the noise. I want to think its not a spun bearing, theres no noise under load or off idle and it hasnt deteriorated even with some relatively hard driving. Power steering pump is a possibility? I cant see that doing it, pulley has no play either. No loose bolts and I dont think its exhaust related, I have no heat shields left on. Oil had no metal in it on draining and hasnt been particularly dirty when changing, so this makes me think no serious internal issue? I cant really see what else it could be though now, b21a's have so little in the engine bay that there are pretty limited possibilities. Hot or cold makes no difference really, although its hard to get the revs low enough when cold to make it do it without the motor dying (carb likes to be warm). I have a noisy throwout bearing but thats a separate issue and a separate noise I can isolate.
Any ideas or things to check?
I thought it was the dizzy, but after swapping to electronic ignition from the points there was no change. Louder on the intake manifold side, Ive tried using a vacuum tube as a stethoscope but no real joy, hard to isolate the noise. I want to think its not a spun bearing, theres no noise under load or off idle and it hasnt deteriorated even with some relatively hard driving. Power steering pump is a possibility? I cant see that doing it, pulley has no play either. No loose bolts and I dont think its exhaust related, I have no heat shields left on. Oil had no metal in it on draining and hasnt been particularly dirty when changing, so this makes me think no serious internal issue? I cant really see what else it could be though now, b21a's have so little in the engine bay that there are pretty limited possibilities. Hot or cold makes no difference really, although its hard to get the revs low enough when cold to make it do it without the motor dying (carb likes to be warm). I have a noisy throwout bearing but thats a separate issue and a separate noise I can isolate.
Any ideas or things to check?
Last edited: