Must I put premium gas in my 1965 Ford F100 390 V8 or can i put regular gas?
I was told that it needs premium gas and premium gas only. But the guy who I bought the truck from said it was a myth and it takes regular gas. What gas does my Ford F100 390 v8 engine take!?
- dtstellwagenLv 77 months ago
If it has a 390 then it's anybody's guess, I don't think they put a 390 in the F100 until 1967. So you probably got either a 352 or swapped motor. My guess is it's a 352 2V (two barrel), 8.4:1 compression— 208 horsepower.
The last one I had ran ok with 88 leaded. I would personally run 89.
BTW Backfiring means unburned fuel is getting into the exhaust. You have an ignition failure or a bad exhaust valve. Nothing to do with octane.
- John AldenLv 77 months ago
If it is non pinging, then regular is fine.
- fodaddy19Lv 77 months ago
If it's the original engine (F-100's could have a 390 2 barrel), then it's a low compression version 8.2:1 or 8.5:1 depending on the year. Those engines could be run on regular fuel without issue and should run on 87 octane just fine. If the engine is not original ( if it has a 4 barrel, then it's was probably swapped in at some point), then you will need to run premium fuel. Those versions had 10:1 compression or higher.
Either way though unless the valve seats have been replaced with hardened ones, you're going to get some erosion and the valves will no longer seal correctly, and you'll lose compression. It's one of the side effects of running unleaded fuel in an engine designed for leaded fuel. If the valve seats have been replaced then you should be fine.
- The DevilLv 77 months ago
Try a half tank of regular just to see if it knocks or pings. If it does, fill the rest of the way with premium. That engine was build originally to run on leaded gasoline, which is no longer available, so unless the heads were upgraded with modern valves and seats, your 390 probably doesn't run well and smokes. Those old 390's had 10:1 compression ratio, so i wouldn't even try to run it on lower than premium fuel today and in 1965, premium was 100 octane.
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- Old Man DirtLv 78 months ago
That old of a vehicle needs only to have its timing adjusted to take care of octane problems
- RonLv 78 months ago
Premium gas in not required