1.7 8v Ignition timing for skimmed heads

[alfa2600]

Hi All

First-time post, long-term Alfisti

I'm in the middle of the final shakedown of my Minari for a track day. Following on from a full engine rebuild and I seem to get pinking/knocking under load. It only happens at lower revs (2k/3.5k) while under load.

For the rebuild, I have done a lot of work on the heads. Basically, they are solid lifters that have been polished and ported and skimmed to the minimum allowed in the Alfa Romeo 33 workshop manual. I can't remember exactly what was taken off them but it was around 1/1.5mm per head.

The engine is going like a scalded cat but I'm afraid I might do some damage during the track day.

I have read up that you should really retard the ignition after aggressively skimming the heads? Has anyone had any experience of this and if so by how much would you recommend to retard the ignition?

Also is there any carb tweaks that may be needed following on the polishing and porting, carbs are standard Dellorto 40's apart from the idle circuit which has been richened.

Colin

[Veesix75]

I don't know the answer to the retarding question, but I'd recommend a rolling road session with someone that knows carbs, it's the only way to know that you have timing and mixture set optimaly through the rev range, especially if you are thrashing it on a track.

Dave Ashford did mine at Brunswick.

Apologies if it is an obvious answer, but money well spent I'd suggest.

[alfettagtam]

In the meantime, don't put it under load below 3-3.5k. On the track you are looking at keeping the revs between 4k and 7k so you shouldn't have a problem. (4k is where the carbs start dumping extra fuel in so that will be why it comes right there.) You've raised the compression somewhat so you really do need to find a carb expert to set them up well - second best to the carb expert + rolling road but my carb expert now does it mostly by ear!

K

[NEG]

Maybe stating the obvious but the quality of the fuel will have a large bearing on the performance and also the advance/retard curve vacuum/weights/springs etc.

[rsfruitbat]

I also would suggest to get the most out of the mods you have done in the safest way then it needs to go on a rolling road or to an expert.
If you are Wales side of the world then I would recommend Dave Young at Mech-Motorsport.

Worked his magic on my car right from dissy and carbed 1600 to ecued and injected 1400.

rsfruitbat