@mexmeister - OK, we're making some progress. Can you still hear pinking, and if so are you prepared to experiment with higher octane fuel to see if that cures it?

 

Regarding the PCV hose, you could replace it by blocking up the top end connection, and fitting a catch can.

4 hours ago, mexmeister said:

Could the existing almost blocked hose have an impact on emissions?

I'll have to see a good photo to understand exactly what mess is in there.

14 minutes ago, KenONeill said:

Can you still hear pinking, and if so are you prepared to experiment with higher octane fuel to see if that cures it?

The pinking should be absent with regular petrol (95). Such experiment is not a valid cure.

Just to let you know that the pickup has just passed its MOT with a CO reading of 0.02% ! The engine temp is now also at 90 degrees when running at normal speed.  At least it looks like the Fun has got a bit more life in it yet.

Thanks to all those who've helped with comments/advice - particularly Ricardo and Ken

Cheers

Good news!

Please read my signature.

The engine was pinking slightly under hard acceleration when I took it for the suggested Italian Tune Up before I took it for its MOT.  However, the existing fuel has octane booster in it.  When I next fill it up I'll put standard 95 RON fuel in and see how it runs.  If it starts pinking more severely, what are my options? (other than continue with the octane booster)

 

Ricardo - I'll try and get a decent photo of the inside of the breather hose, but I'm not going to be using the pickup until the weekend. 

Ken - Ref fitting a catch tank - thanks for the suggestion, but I think I'll try and get the correct hose or maybe find an alternative instead.  If all else fails, I'll probably assemble my own. 

Thanks again for your help


 

6 hours ago, KenONeill said:

Regarding the PCV hose, you could replace it by blocking up the top end connection, and fitting a catch can.

The upper end of the hose is going to air intake and the lower end goes to an existing oil vapors separator. There is no logic at all in your suggestion.

 

21 minutes ago, mexmeister said:

When I next fill it up I'll put standard 95 RON fuel in and see how it runs.  If it starts pinking more severely, what are my options? (other than continue with the octane booster)

Read again my post.

16 hours ago, RicardoM said:

The pinking should be absent with regular petrol (95). Such experiment is not a valid cure.

We know that:-

1. The head has been skimmed, but not by how much.
2. Unless the combustion chamber is machined out to re-instate the standard volume, skimming the head reduces the volume.
3. Compression ratio is given by swept volume divided by CC volume.
4. A higher CR needs more advance and/or higher octane fuel to prevent detonation.

You'd agree those points I presume?

28 minutes ago, KenONeill said:

A higher CR needs more advance and/or higher octane fuel to prevent detonation.

True. In practice, a stock 1.6 engine has a compression ratio of 9.8:1. A stock 1.3 MPI engine has a compression ratio of 10:1 while still using 95 unleaded fuel from factory. I doubt the cylinder head was skimmed up to needing a 100 unleaded petrol. Moreover, and this is overlooked by the OP so far, the engine has a knock sensor that should signal to ECU when pinking occurs and in turn it should adjust the ignition timing accordingly regardless of compression ratio modification (of course up to a given point). The knock sensor might be faulty or overtorqued.

18 minutes ago, RicardoM said:

True. In practice, a stock 1.6 engine has a compression ratio of 9.8:1. A stock 1.3 MPI engine has a compression ratio of 10:1 while still using 95 unleaded fuel from factory. I doubt the cylinder head was skimmed up to needing a 100 unleaded petrol. Moreover, and this is overlooked by the OP so far, the engine has a knock sensor that should signal to ECU when pinking occurs and in turn it should adjust the ignition timing accordingly regardless of compression ratio modification (of course up to a given point). The knock sensor might be faulty or overtorqued.

OK, I wasn't aware of the knock sensor. I'll cheerfully agree that checking it is a better idea than using higher octane fuel.

 

That said, before knock sensors, I'd have different standard engines with anything from about 8.5 (non-turbo) to 10 to 1 CRs running the same octane.