65 396/425, what octane of gas?

[William B.]

Recently purchased a 65 coupe with 396/425hp, very originol car 29k miles. Was running great on the tank of gas that came with the car, refilled with premium tonight and the car pings any time a load is applied.
Bought STP octane boost ran another 20 miles still pings alot.
Do I have to put more miles on it, or pump out the gas and go look for a higher octane?

Any help or suggestions will be appreciated.

[John H.]

Re: 65 396/425, what octane of gas?

Bill -

"Octane boosters" are essentially useless.

Do you have any history on the engine? Has it been rebuilt with other-than-stock components?

Suggest you put a dial-back timing light on it and map the advance curve first so you know what the initial advance setting and centrifugal advance curve look like, and if the vacuum advance is functional; that will provide some useful diagnostic information to work from.

[Edward S.]

Re: 65 396/425, what octane of gas?

Bill, Wish I could help, I have had a L78 for 8 years now and have never had a pinging problem. I use Sunoco 94% and the car runs great.

[William B.]

Re: 65 396/425, what octane of gas?

I will check timing, just to make sure today. The car ran so good before, I am thinking it is just the gas. I have never used an octane booster, has anyone used it before, what should I expect?

[Joel T.]

Re: 65 396/425, what octane of gas?

I will check timing, just to make sure today. The car ran so good before, I am thinking it is just the gas. I have never used an octane booster, has anyone used it before, what should I expect?

Bill;

I have a '65 396/425 which was recently rebuilt... My CR is 10.25. The car will run fine on pump gas so long as the timing is correct, 8 degrees as I recall.

Joel

[Michael W.]

Re: 65 396/425, what octane of gas?

I have never used an octane booster, has anyone used it before, what should I expect?

An empty pocket with nothing to show for it. Most 'octane boosters' have minimal or no effect. Many advertise that they will increase octane by 1 point. What they mean is raising 92 octane to 92.1 octane.

[Jim T.]

Re: 65 396/425, what octane of gas?

What do you use in your 1966 427/425?
Did the seller of the 65 fly an airplane, if the person did, access to AVGAS with higher octane and with some lead would of been easy and could of been in your new 1965.

[Bill C.]

Re: 65 396/425, what octane of gas?

You can get the MAXLEAD 2000 or LEAD SUPREME 130.

It is real TEL and it rasies the octane rating real FULL points.
I would imagine your car needs around 95-97 octane to run as configured from GM.

Starting with 93 as a base, 2 ounces per gallons of fuel will get you around that range.

The stuff really works, I use it all the time.
Only issue is lead, you will change your plugs more often just becuas of the deposits.

I blended a 5 gallon pale using the lead supreme for a race car with 12:1 compression ratio. I used an entire quart and the car ran just fine at the track.

My two cents ....