Pinking at low revs?

testrider

testrider

Active Member
Over the last couple of weeks I've noticed a metallic rattly sound coming from the engine. It occurs between about 1800 and 2200 RPM on light throttle - opening the throttles more during these revs stops it and it doesn't happen anywhere else in the rev range. The engine feels as strong as normal and pulls well throughout the rev range.

Could this be pinking or should I be looking for a loose bracket or clamp (which I'll do when it stops raining!)?
 
I know I have a faulty tappet when the engine isn't pumping so much oil around, normally in the lower regions of the rev range but I think that is not the case due to the revs your hear the noise at. If it is pinking, try to increase your octane level. A Canadian with a Plymouth Roadrunner told me once he drove to his local airport, bought 100 liters of avation fuel and added about 2 liters to every 50. Increased his octane to about 108/110 he thought, madness! Otherwise reduce your ignition advance and see what happens. Hope to have helped you a little..
 
rockdemon said:
Vacuum advance in the dizzy maybe?
Click to expand...

I wondered about that, but I checked it last month when the inlet manifold was off. At what revs does the vacuum advance start to move?

I'm using 95RON petrol as normal and the last 3 tanks I used last week were from different places so I've eliminated bad fuel.
 
Have you uprated your timing gear? Or still original? If original I'd check it hasn't moved!
 
I fitted steel gears and a new chain when I rebuilt the engine about the same time as Vaultsman did. Nothing else about the engine's performance is suspect, just this brief rattle on part throttle around 2000rpm.

I always though pinking only occured with wide(ish) open throttle in the lower rev range and you cured it by lifting off or changing down, but this is on light thottle and is cured by opening the throttle more.

I think I need to don a Sowester and search for some loose bolt or bracket before I do anything else.
 
If this rain persists, whilst you are out fitting an outboard motor, try giving the exhaust a good shake.



John.
 
Just a thought,

had a similar rattle develop suddenly couple years ago whilst on a small club road-run
through Wales, had me worried all day at around 1800 - 2000 rpm only - turned out to be the exhaust gearbox
support bracket bolt had lost its nut & washer- soon cured at home next day car up on ramps (in the dry weather ! - when was that !!!!)

Hope your problem is that simple.
 
I'd have a look at the exhuast too.
When my car was laid up last winter, I went out once a week to run the engine for a while. I was getting a rattle at just below 2000rpm. I had convinced myself that it was timing chain rattle. Come spring/summer when I was finishing off welding work, I found one of the exhaust downpipe to front section flange bolts had a loose nut. I tightned it up (and put an extra locking nut on each to stop them working loose again). Never thought too much about it till I started the engine next time and the rattle had gone :D . I had been near convinced it was timing chain rattle (which I used to get till I did some head work a few yers back and tightned up the chains when I put it all back together).
 
The sticky bun goes to Mike J and Steve!!

The nuts on the exhaust clamp on the bracket from the gearbox were loose. I've done them up tight now and although there was no time to test drive it today it looks like the culprit.
 
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