Engine Rattle

[chris_bates]

I have noticed that some A series engines have a deep metallic rattly note as they rev beyond say 2500 rpm. A new tight engine doesn't tend to do this. I have rebuilt the current 1098 engine in my pick up and have excellent oil pressure and the "rattle" is certainly not big ends or mains. I also fitted a new duplex timing chain so I doubt it is anything to do with timing chain rattle yet it seems to have the same note you would expect if you tapped the sump or timing chain cover. It is timed at the same rate as the engine revs.

I certainly did not have this "rattle" in the 948 saloon I had as a youngster but did experience it in a clapped out series 11 I helped dismantle in 1960......? Also it was not present in the 1275 engine I had in the Midget I had.

It obviously has something to do with wear somewhere in the engine but nothing that would seem to affect performance. I would love to know the views of more experienced mechanical experts as long-term it is something I'd like to sort.

Thanks

Chris

[bmcecosse]

'Rebuilt' - in what way? Reground crankshaft ?? Or just new shells...... What is the HOT (after a good hard run) oil pressure at 40 mph in top gear? What other work was done to the engine - rebore?? Or just new piston rings? Could simply be 'pinking' of course! Retard the ignition timing and see if it disappears. Is the engine bog standard? Would not normally fit duplex unless using a high lift cam and/or heavy valve springs.....

[chris_bates]

BMCecosse, thanks for your reply. It was a very basic rebuild, ie just new bearing shells, both mains and big ends. The crankshaft seemed to be ok and the old shells had not worn through and were only slightly scored. The idea was that this engine would do until I got round to doing a proper rebuild on the one I took out with a 940 head which was smoking a bit too much!

40mph psi hot about 50, and about 20 on tick-over. I fitted a duplex timing chain as the cost over a single was not that much more and the old chain sprocket wheel (plastic guide thing) has started to disintegrate!

It is not a pinking sound, more of a metallic knocking as if someone is tapping the sump very quickly although if I had to place where it was coming from, I'd say from the camshaft area so it could be that there is some sideways movement in the pushrods??

Chris

[bmcecosse]

Oil pressure is ok then. Could be piston slap I suppose. Duplex is no assurance against chain rattle......which mine does in spades when idling...... Not pushrods - suppose it could be cam followers - easy enough to pop them out and have a look- just slacken the rocker adjustments enough to pop the push rods out to the side and then lift away. It's also possible the duplex cam sprocket is perhaps touching the timing case cover -especially if it has a vent ?? But not unknown with standard cover. If so, you will soon know as it machines a hole in the cover......

[IslipMinor]

When you fitted the duplex timing chain, did you countersink the front plate and fit countersink screws in the bottom 2 holes of the front plate, behind the crankshaft timing sprocket?

[bmcecosse]

Good point Richard.........

[katy]

It was a very basic rebuild, ie just new bearing shells, both mains and big ends.

I sure as heck wouldn't call that a rebuild.
A proper rebuild would include, but not limited to: reground crankshaft, new bearing shells, cylinders rebored, new pistons and rings, new gudgeon pins (wrist pins in my lingo), resized, aligned connecting rods, new oil pump, new or carefully inspected or reground camshaft, new camshaft bearings, new timing chain and gears.

[chris_bates]

Thanks for all the replies.

Richard, yes I did countersink the screws so the timing chain should not be an issue. The noise is a tapping that could be big ends except it is the wrong sound and comes on when the engine reaches a certain speed rather than when under load. I suspect it is more likely to be the cam followers as bmc ecosse suggested as the sound definitely comes from that side of the engine.

Katy, I agree that my "rebuild" was hardly thorough and I certainly did not expect a nice sweet engine afterwards. The engine I took out was smoking a lot so I suspect that will be a rebore job at the least, but at least with this engine it goes, was a cheap temporary solution and keeps me on the road, albeit with a few rattles.

Incidentally, I have now changed to accuspark (another cheap solution) and so far it has made a huge difference to the performance especially at low revs.

Thanks again for your thoughts.

Chris