Engine Pinking under load

[contractman]

Hi

I have a 1500 Spitfire, which I am aware has worn valve guides, odd puff of smoke here and there and above average use of oil - its on my to do list.

The engine has always pinked a bit under load, but more recently after another few thousand miles its doing at the slightest incline.

I have covered the usual, higher octane fuel and retarded the timing but no real improvement this time.

My questions is - will worn valve guides enhance the noise when driving or allow the engine to pink more in these circumstances?

Cheers

[CyTry]

Thinks... not sure.  What effect do worn valve guides have?  If oil gets in the cylinders and has burnt on / they are coked up, then the 'coke' remains hot and causes pre-ignition?  Just thinking.

[Don Cook]

When you switch off does it run on? I'm thinking a head off job is needed: 1. to replace the guides, 2. to re-cut and lap in the valves 3. clean up all the crud that's probably causing pre-ignition 4. maybe fit new rings.

[Velocita Rosso]

Quoted from Don Cook

When you switch off does it run on? I'm thinking a head off job is needed: 1. to replace the guides, 2. to re-cut and lap in the valves 3. clean up all the crud that's probably causing pre-ignition 4. maybe fit new rings.

Ditto

[RedRooster]

3rd that.

[drofgum]

Hi,
Along with the preignition symptom, oil has a lower octane rating than petrol. So having some oil mixed into the charge will promote pinking.
                                                                                         Regards,
                                                                                         Paul

[Dannyb]

If you are getting lots of oil forced out of the breather back to the carb intakes that can cause your problem. Try disconnecting the breather pipe from the rocker cover and  block off the two carbs where the pipes attach or loop them with a pipe. Then see if it pinks.

[Ken Young]

Pinking can also be caused when there is a hole in the head gasket between two cylinders. This also causes back flow to the carbs and obviously low performance.  The pinking sound is the push rods bearings breaking through the oil seal and causing metal to metal contact with the crankshaft like a hammer. This is BAD. Unless you want a far bigger engine rebuild in the future, I recommend  you recondition the head as above and whilst you are at it do the same with the carburettors. Don't drive  far with the pinking sound! Ken