Noisy Engine

[Graham Barker]

Andrew Ruby's recent post about a mystery engine ailment and John Cornforth's suggestion that distributor not advancing correctly might be a cause has got me pondering further on the noise of my 3 bearing Ruby engine. 
At higher revs, e.g above 40 mph in top gear the engine becomes decidedly noisier.
Could the distributor not advancing correctly be a cause of the noise?
I know that the distributor is only giving about 5 degrees of advance because the holes for the weight pivot pins have become a bit oval. I have set the timing to give good uphill performance at 30 mph in top gear, so the timing may not be correctly advanced for speed above 40 mph.
The reason for not correcting the ovality of the pivot pin holes is that I couldn't punch out the pin that holds the pinion gear to the distributor shaft. Is there a good technique for doing this?

[john williams]

Usually, if the ignition is under advanced[retarded] the engine tends to run quieter. I would suggest you retard the ignition slightly, and see if that reduces the noise.

[Chris KC]

I'm inclined to agree, slogging up hill in high gear is actually the worst case for ignition advance, if it's correct there it's retarded everywhere else.

As for removing the gear pin, if you can't drift it out my next port of call would be to file it flush and drill it out - carefully jigged in a pillar drill to have a sporting chance of keeping in alignment. Use an undersize bit at first to limit collateral damage. If you do mess the hole up rotate 90 degrees and drill a fresh one.

Finally if I had a 3-bearing engine with a suddenly noisy bottom end I'd whip the sump off and look for any sign of cracking across the circular webs. There is sometimes a brief period of grace before they let go completely.

[Graham Barker]

Thanks, John and Chris for your replies. You have confirmed my suspicion that retarded running tends to be quieter than advanced running. 
The noise has always been there since I bought the car two years ago. I have done 500 miles in it. The previous owner had only done about 500 miles after having the engine professionally rebuilt. The noise does sound like bottom end rumble, which I wouldn't expect after a professional rebuild. Hence my asking about whether ignition retarded could cause the noise.

[Ian Williams]

You might want to check your CTR main for play. Improperly assembled this bearing will be not last long and then make all sorts of rumblings. A professional rebuild, especially here in NZ, is no guarantee that it has been done well. Play in timing gears and dynamo is also a good source of noise.

[Chris KC]

Upon reflection, if we assume the crank was sound when installed (bit of a leap), it shouldn't be letting go 1000 miles after rebuild, however badly it may have been done. But I heartily agree with Ian's comment, well worth checking condition of the centre main bearing (and the copper pipe which feeds it with oil), and you can cast an eye over the crank at the same time.

[AustinWood]

If the holes in the distributor base plate are worn and become oval that will cause excessive advance. That in turn will make the engine noisy at higher revs.
I checked the advance on the distributor in our car using a 12V timing light. I connected it to a 12V battery and the No1 plug lead on The Austin. I made a mark on the fan pulley with the engine at approximately No1 TDC. I could then watch the timing change with engine speed. In our case in moved steadily and smoothly.
The advance mechanism of old DK4 distributors is a bit crude, and when worn I suspect they often don't work at all or else go straight to full advance.

[Graham Barker]

Thanks Ian, Chris and Jim for your replies. 
I will be following up on checking the main centre bearing and the crank. 
Jim, I had fitted new springs to the distributor weights and checked that they move freely. When I twist the spindle I get about 3 degrees rotation before the weights start to move out. This appears to be taking up the ovality of the pivot pin holes. I then get a further 5 degrees of twist bringing the weights to full out position.  Hence I suspect that at idle the ovality is already taken up and I will only have 5 degrees of advance available for higher revs. 
I have set the timing by road test to give good uphill performance at 30 mph. Advancing and regarding the timing from this setting doesn't change the noise coming in above 40 mph, but does affect the uphill performance. That's a pity because I will have to look at more difficult remedies than ignition timing.

[Reckless Rat]

Are the engine mountings loose?