I am preparing to have the engine rebuilt in a my Giulietta Spider. My question: Anyone having difficulties with driving 91 octane pump gas in their higher compression Veloce motor? Any reason to be concerned with 'pinging'.
It really depends on your engine builder, and how close to a "stock" Veloce engine you plan to build. If cams are standard Veloce, and compression remains in a reasonable range, 9.7 to 10.5 maximum, and head work is done properly without milling other than a possible minimal skim cut, 91 RON should be ok. Any ping or knock leads to rapid Alfa engine death. A stock 1300 / 1600 Veloce engine can run fine on todays "premium" fuels.
If you are creating a Veloce engine, from a Normale, be sure you have access to an ALFA engine builder, not just an "engine builder". There are many areas where problems, particular to Alfa engines, will need to be addressed. Gordon Raymond
I run octane boost in several of my older high compression engines. Amsoil has about the most effective one sold in the US. I can run the car without the boost if I retard the timing and run the air fuel mixture a bit rich, but it runs better with the boost in there and not detuned.
One more note. In California at least, the gasoline has been altered so much the past 10 years, you may need to rejet the carbs from stock setting to get the cars to run right. The current formulation is designed for high pressure fuel injected cars, and is a lighter viscosity and lower energy than the older formulas. I had to richen up the jets on most of my cars to get them to run a good A/F ratio
I haven't had any trouble running on Calif 91 octane fuel, but will agree that tuning is a big issue. Stock jetting didn't get it on either of my cars. And, those old dizzy's are often a source of trouble too.
I think adding a little note here is worthwhile. Having watched any number of Alfa street, and race engines run up on an engine dino, The point of maximum Hp, or torque happens just as the mixture goes to, TOO lean! Ignition max advance can play a part, but it is more often the advance curve that becomes a problem. Many tuners, myself included, like to err on the rich mixture side, with not quite all the advance that would yield absolute maximum performance. Then if the air is COOL, or other conditions do not mach the test condition, no harm done! I run a GTA engine on the street, on pump gas 93 RON, no ethanol. My dino sheet shows 169 corrected Hp. On the street, slightly richer on the high speed jetting, and with 1 / 1.5 degrees less advance, I've probably 150-155 Hp, with no problems and that's just what you want. Gordon Raymond