My 1972 Fiat 850 Spider has an odd issue. It’s a random tapping noise that seems to get worse after the engine is warm or it’s been driven a while. I don’t think it can’t be the valves because of how random it is, and I tried disconnecting the belt that goes to the alternator and water pump but it didn’t change. It seems to rattle louder when it’s under load as well, but it’s hard to tell. I’ve narrowed it down (at least in my head, I could be wrong) to either the timing chain or the distributor since that seems to be the general area where the noise is coming from. What do you all think? Thank you for any help you can give me! (Apologies for how dark the video is.)
Technical Any idea what this tapping is?
- Thread starter Matt129
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Technical Any idea what this tapping is?
Tricky, could be timing chain.
Can you eliminate valve gear by seeing if louder with oil filler cap off (don't get an ear full of oil splashes) or see if it goes quieter by tipping half a pint of engine oil in whilst running as it goes straight around the valve rockers etc. Can be a bit messy though.
Have you tries a "listening stick" a long screwdriver carefully placed and held against your ear, there are car "stethoscopes" available also to locate noises?
I’ve tried with a long screwdriver, seems like it’s coming more from the timing chain area rather than the valve area but it’s really hard to tell. Definitely isn’t a rod knock though I would think right? Yes they can be inconsistent like that rattle but it seems too high pitched to be a rod knock, and I think if it were a rod knock it would have blown or gotten significantly worse with how many miles I’ve put on it since buying it a few months ago and not being sure if that was just a normal vintage Fiat noise at first.
I agree doesn't sound like con rod or big end bearing etc.
If you get the chance try what I suggested.
Apart from that, as an apprentice around 1969 we often had small Fords, Anglias and Cortinas that rattled from the top end due to wear in the valve gear generally, pouring the oil in often helped locate the noise. Often when valve gear was removed to inspect, the bushes in the rockers were worn on the shaft they pivoted on making it hard to accurately adjust valve clearances etc.
Having said that single row timing chains when worn tended to be noisy too.
You may find if revs slightly increased as it does so it could take the slack up in a chain for an instant and affect that source of noise.
I took the oil cap off while it was running and tapping, the noise wasn’t any louder. I’m thinking it has to be the timing chain because it sounds lower on the engine and somewhat external almost?
With engine off, put a spanner or socket on the crankshaft pulley and gentle rock it to feel if any unusual slack forwards and back, as in timing chain before it turns the camshaft, this may be a guide though depends on the design of timing chain tensioner as to how accurate, if excessive it can be a worn chain or tensioner.
After doing this test turn the engine in the correct direction a bit so that when starter turns it doesn't have to take up any unnatural slack before starting.
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Hi matt.
It sounds like a worn camshaft to me. It would likely mean replacing the camshaft and followers and do the timing chain at the same time. You would also need the sump to come off. It can be done in the car but you will need to rear panel to be removed. Often wear is on lobes 5,6,7 or 8 from the timing chain end so it difficult to look through the fuel pump hole and see that end even with an endoscope. Once done you will have a lovely sounding engine.
Best way of finding out is post a video on here of the engine turning over but with the coil lead disconnected so it won't start. If you sense a different compression on the cylinders as it turns over then its likely camshaft.
Tim
It sounds like a worn camshaft to me. It would likely mean replacing the camshaft and followers and do the timing chain at the same time. You would also need the sump to come off. It can be done in the car but you will need to rear panel to be removed. Often wear is on lobes 5,6,7 or 8 from the timing chain end so it difficult to look through the fuel pump hole and see that end even with an endoscope. Once done you will have a lovely sounding engine.
Best way of finding out is post a video on here of the engine turning over but with the coil lead disconnected so it won't start. If you sense a different compression on the cylinders as it turns over then its likely camshaft.
Tim
It spins over evenly, no “galloping” or anything like that. And it actually runs really well otherwise, I would imagine if it had a worn cam lobe it would be running rough etc but it fires on all cylinders and seems fine otherwise.
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Hi Matt.
Info on the cams for you.
If you have wear on the front and rear of the top of the lobe basically making it triangular you won't get galloping at this stage but noise from the engine. This will cause damage to the followers( consumable anyway).
If its worn more than that such that it starts to wear down the top of the lobe then this will start the galloping sound and compression on different cylinders will be measured with a compression test.
Tim
Info on the cams for you.
If you have wear on the front and rear of the top of the lobe basically making it triangular you won't get galloping at this stage but noise from the engine. This will cause damage to the followers( consumable anyway).
If its worn more than that such that it starts to wear down the top of the lobe then this will start the galloping sound and compression on different cylinders will be measured with a compression test.
Tim
Should I still be okay to drive it at this stage if it is the cam? It sounds like a very complicated fix
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Hi matt.
There's no reason to stop driving it as a worn xam shouldn't cause any damage to any other components apart from the followers. If its driving fine but with this noise then I wouldn't stress over it.
Just keep an ear out for the car to start the galloping on start up. This will then give you time to get things ready.
Tim
There's no reason to stop driving it as a worn xam shouldn't cause any damage to any other components apart from the followers. If its driving fine but with this noise then I wouldn't stress over it.
Just keep an ear out for the car to start the galloping on start up. This will then give you time to get things ready.
Tim
Cam wear tends to be progressive , I have stripped Ford pre crossflow engines in the past for burning oil, that were running quite happy with some cam lobes almost oval rather than a peak.
Mind you they did benefit with a new cam and followers along with the rebore and pistons, crankgrind and shell bearings etc.
Mind you they did benefit with a new cam and followers along with the rebore and pistons, crankgrind and shell bearings etc.
Any way I can prolong the inevitable more or less? Just to keep the cam alive as long as possible?
Is there any way I can tell for sure wether it’s a camshaft or the timing chain causing the noise?Cam wear tends to be progressive , I have stripped Ford pre crossflow engines in the past for burning oil, that were running quite happy with some cam lobes almost oval rather than a peak.
Mind you they did benefit with a new cam and followers along with the rebore and pistons, crankgrind and shell bearings etc.
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Only definitive way to know is to inspect both.
Worn timing chain will give you a wide light band when using a strobe light for setting up the timing.
To prolong the life of a camshaft. Keep the oil in the best condition you can.
Tim
Worn timing chain will give you a wide light band when using a strobe light for setting up the timing.
To prolong the life of a camshaft. Keep the oil in the best condition you can.
Tim
Listening stick I mentioned earlier may help locate noise.
