Should I be running Supreme Gasoline or high octance gas in my 1971 240z? I just rebuilt the engine and was wondering what kind of gas I should put in it?

High octane is only required if the compression ratio is high enough that the engine would pre-detonate (ping) otherwise. For a stock engine regular should be fine.

My engine does "ping" in third gear....so I prob should use a higher octane gas?

My stock '71 needs premium, and the owner's manual specifies premium. You might get away with less octane if you have a later cylinder head, or a hot cam installed. But for a stock '71 L24, I'd recommend premium.

At what RPM does it ping in 3rd?

Since Arne's engine is different than mine I suppose you should consult the factory service manual for your particular model. For mine, 1972 L24 with twin SUs and an 8.8:1 compression ratio the FSM specifies "more than 95" for octane. Where I live I can only buy 87, 91, or 93. It also specifies with emission control to use "91 (low lead)". I mostly use 87 and never notice pinging.

How's the timing? What dizzy are you running?

Might not be fuel related. Some cars will ping if the timing is off even with higher octane fuel.

Chris A.

Here's some interesting reading on knocking and pinging. List at the bottom of the article with many things that could cause pre-ignition.

http://www.omegamotors.com/enjoy/gasoline/gasoline_07.html

Chris A.

Timing is good.....just checked it. Not quite sure of the RPM in third gear. I just remeber that right when i shift into third (at a lower RPM) it Pings. Im going to try and put a octane booster in the tank now because i have the low level octane in it now and next time I am going to get supreme gas. Hopefully it will get rid of the pingen.