What Fuel to use in a 1966 Stang?

[bigbandjohn]

I almost forgot the most important question!

Older Mustangs were built when Leaded fuel was used. Since we don't have leaded fuel anymore, what does everyone recommend that we use for fuel in our classic Mustangs?

66 - Slant 6, 3spd

I'm going to try to post a poll option here for quick feedback, but I do what to hear reasons as well. Forgive me if I get it wrong.

[PKRWUD]

You have to have to take the head to a machine shop and have hardened valve seats installed. As far as octane, the best gas to use is the LOWEST octane you can without detonation.

I don't feel like entering all the info again, so here:

The Truth About Octane

Take care,
~Chris

[mustangII460]

If its a daily driver hardened seats will be in order. If its not every day a lead additive works fine. I used to keep a bottle in the trunk. When I filled up I poured a little into the pump nozzle and then put it into the filler neck. Eliminating a funnel. Walmart has it.

[bigbandjohn]

Originally posted by mustangII460
If its a daily driver hardened seats will be in order. If its not every day a lead additive works fine. I used to keep a bottle in the trunk. When I filled up I poured a little into the pump nozzle and then put it into the filler neck. Eliminating a funnel. Walmart has it.

Thanks. Now I have a stupid question... What do you mean by hardened seats?

[lx mike]

The valve seats. the lead that used to be in gas lubicated them and now without the lead to lube them they get messed up.

[nicolette]

In my daily driver, i use 93, with a bottle of lead additive called 'instead o lead' from wal-mart. i've tried each gas, with and without the additive, over the couple of years i've had my beastie. although i know nothing of the technicalities of it, she runs a heck of a lot smoother with the 93, and for a rooted, 6 cylinder,badly needing an overhaul engine, i figure a little babying won't hurt! another thing i've noticed is that over time with this combination, my milage had gotten better. either that or my speedometer is rooted too!

[Kisner]

I'm confused (as usual). What fuel should I be running in my 68 coupe, 302 4V? Right now I'm running 93 octane unleaded.

[PKRWUD]

Originally posted by Kisner
I'm confused (as usual). What fuel should I be running in my 68 coupe, 302 4V? Right now I'm running 93 octane unleaded.

The lowest octane you can, without pinging.

Try putting in half a tank of 89 next time, and see if it pings. If it does, go up, if it doesn't, go down.

[Kisner]

I should have been more specific. Do I need to be adding a lead additive?

[Rev]

Listen to PKRWUD. It's just what he said.

Rev

[Kisner]

Thanks for the info. Just wanted to be sure I didn't need a lead additive. I've always used unleaded fuel only because the only reference I could find was in my reproduction copy of the orginal owner's manual. It said to use premium fuel with at least a 99.8 octane rating for a 302 4V. I "assumed" they meant unleaded when they said premium since there was no mention of leaded or unleaded fuel. I've always used the 93 (highest I've ever seen in my area) since the manual said a minimum of 99.8. I'll go with the 89 next time and see if it pings.

[PKRWUD]

First off, thanks Rev.

Second, how many miles are on this engine? It has to have had hardened seats installed because leaded gas hasn't been available for what, 10 years? If it hadn't been done, your engine would have sucked a valve a long time ago, so you don't need lead.

Nevermind.

[Kisner]

A long story on the engine. I'll try to make it short as I can. Was my father-in law's car. In 94 he had 289 taken out and a 302 put in. Engine was sooped up with Edelbrock 600 cfm carb, performer 302 intake, semi-radical cam, bored out 30 over, and everything else put in brand new. A so-called friend of his took the car to restore about a week after the engine was rebuilt, completely disassembled the car, and stole around $5,000 from my father-in-law over 4 years and did "nothing". Father-in-law passed away in 98, I inherited in pieces in 99, and just completed the restoration. Car hasn't been driven in 8 1/2 years and probably has 30 miles on the rebuilt engine. I've cranked it every weekend the past 3 1/2 years and changed the oil every 4 months. The mechanic can't be found and I have no idea what's been done or what's inside the engine. It sounds sweet and tomorrow afternoon it will hit the road for the first time (very short trip to start out with). I know everything there is to know about the bodywork and assembly on this car, but I am clueless and know nothing about engines. That's why I ask so many stupid questions. I don't mean to be offensive or insulating in any way. I'd also like to know if anyone foresees any engine problems I may have since the vehicle hasn't been street driven in almost 8 1/2 years. Thanks again for all the advice.

[PKRWUD]

I'm sure it has hardened seats, then, and like everyone's shop teacher used to say, the only stupid question is the one you were afraid to ask.

If it's only got 30 miles on it, you need to be sure the rings have seated. Go to a large, empty parking lot, or an empty street in an industrial area, and from a rolling start, gun it for 2 or 3 seconds, and let in wind down, then gun it for a few seconds, then let it wind down. Don't use your brakes, just leave it in first, and do this 10 or 12 times.

Drive it conservatively for the first 500 miles, and stay away from long, steady high rpm driving (no road trips on the freeway) for at least 750 miles. Change the oil and filter again, and you're good to go.

Take care,
~Chris