Re: [FWDLK] Correct Octane Gas for Our Cars

If you are running 89 now with no ping then 87 should work….

With today’s modern ‘blend’ fuels I have found it pays to make sure all of your seals in the fuel system are alcohol resistant. I have also found I need to jet the carb slightly richer to compensate. I have seen a few muscle cars running on E-85, and that is how they are doing it. I am told the ethanol has a higher octane rating??? Haven’t confirmed that, but don’t drag cars that run alcohol basically running on ethanol, just pure- no gas mixture??. Of course, you should already have hardened valve seals installed in the heads, that eliminates the need for lead entirely.

I’ve run almost all of my Chargers on 87 octane- and that with the factory 10-1 compression rating with just the above mods….mileage WAS terrible though- 8 to 12 mpg….but they have all be 383 or 440 cars…

Enjoy!

Charles.

From: Forward Look Mopar Discussion List [mailto:L-FORWARDLOOK@xxxxxxxxxxxxx] On Behalf Of cgico@xxxxxxxxxxx
Sent: Tuesday, June 30, 2009 11:33 AM
To: L-FORWARDLOOK@xxxxxxxxxxxxx
Subject: Re: [FWDLK] Correct Octane Gas for Our Cars

----- Original Message -----

From: Ron Waters

I've always used mid-grade octane gasoline for my 58 Plymouth with a 318.

Here on the east coast, mid-grade is 89 octane. I was told recently that 87

octane would be fine for this engine. When I questioned this in comparison

to the old 89 octane leaded gas that we used to put in our cars, I was told

that octane is now calculated differently and, again, the 87 octane would be

fine.

What do most folks use for small blocks engines like the 318 ?

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Ron,

Since most of us face an engine rebuild in the course of a restoration, a key consideration in the driving of said vehicle is the fuel you want to use and the availability thereof.

As Jim mentioned, fuels have changed and thinking in terms of 1950's tech, it simply does not compute to what is going on today. You can run low grade fuels with perfectly fine results if a few adjustments are done when building your engine. Dropping compression is the first step, followed by changing your camming and carb settings to compensate. I run 8.5:1 pistons in all my rebuilds, and even in the 440 magnum have no trouble getting the car sideways on 87 octane with no pinging.

A lot of the old heads were buying $5 a gallon av-gas (when regular was under $2) and hanging on to the old school thinking that you had to have the octane to make it work. Well, maybe so in an old school engine / car, but most of us are interested in driving and enjoying the cars with a lower level of fuss than knowing where the local airport is along our routes of travel and make some changes.

You should be fine on 87. If not, talk with a good motorhead / tech and find out what engine mods best suit your needs.

B.

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