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Discussion Starter · #1 ·
Thinking of selling my C6 convertible and going back in time again.

So, anyone have a 350 CI 350 HP 11 to 1 CR stock 1969 or 70 and do you have any problem running 93 octane? Pinging, etc.? I remember my 70 LT1 did not like it at all. Thanks.
 

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You could "possibly" get some pinging but it's really more about the tune up. Remember the factory compression ratios are usually optimistic....I would be surprised if that 350/350 actually even had a true 10.0-1. Just get the ignition curve right, limit the amount of vacuum advance it gets and you should be fine. Going down a heat range or two on the plugs won't be a bad idea either... Odds are that most 350/350 cars you buy will have enough mileage that the engine will be "worn in" anyway and not likely anywhere near 11-1...

FWIW....my 496 has iron heads, has a measured 10.0-1 comp and runs perfect on 93 oct. But I keep my total timing at 32* and only add 4.5* of vac advance at idle/cruise. I have burned a head gasket on it from detonation before I figured out 38* was too much....:down:
 

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You could "possibly" get some pinging but it's really more about the tune up. Remember the factory compression ratios are usually optimistic....I would be surprised if that 350/350 actually even had a true 10.0-1. Just get the ignition curve right, limit the amount of vacuum advance it gets and you should be fine. Going down a heat range or two on the plugs won't be a bad idea either... Odds are that most 350/350 cars you buy will have enough mileage that the engine will be "worn in" anyway and not likely anywhere near 11-1...
:agree: I rarely have any issues running 91 octane in my '69 L46 with 36* of timing. Occasionally a little knock up near redline, but not all the time.
 

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Discussion Starter · #4 ·
:agree: I rarely have any issues running 91 octane in my '69 L46 with 36* of timing. Occasionally a little knock up near redline, but not all the time.
Interesting. My 70 LT1 did not like 93 octane, maybe it was the cam vs. to L46 cam specs.

I loved my 66 with the 327 300 HP, instant throttle response and great low end torque.

I would really like to find a 427 or 454 390 hp (69/70) with the 10.25:1, that should be very safe with 93 octane.

Do you run stock plugs or one range colder? Thanks.
 

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I rebuilt my top end on my 81 350 with Alum heads and a new cam but the bottom end stayed stock and after setting the timing (very advanced due to the cam) she runs great and I only put in 91-93
 
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