1964 Mercury Comet 404 Sedan Inline 6 - what can I do to make engine to run best with today's fuel?

In terms of the valve seats, I would drive the engine until you need to do the work. You'll know because of the oil burning. Lead substitute will stall that for a long time. The fuel lines and carb I would plan on now, before things go wrong. Having the rubber fail because of the modern fuel could really mess the engine up, forcing a rebuild very prematurely. The other thing I would do, especially if you plan to drive the old girl much, is to switch to radial tires. they will make a big difference. If you drive her quite a bit, especially in hilly or highway conditions, is to convert the brakes to a dual master system, with front discs. The good news is that the Mustang parts are all readily available for a reasonable cost, and are a direct bolt in.

Thanks Very Much for this excellent advice. I will replace the "rubber"... and as much of the rotten stuff I can find and take a closer look at the old wiring while I'm at it. I never thought about or thought there could be rubber compatibility issues with modern fuel chemistry. I do plan on driving it regularly. I'm not sure about the carb but I can rebuild it just for fun and certainty. I love the idea about upgrading the brakes... I'm sure that question was lurking right behind the present one. I have some great scrap yards around me and a good mechanic up the road who takes great care of me and my cars. I'm going to be picky and spend the extra bucks as necessary on the tires... I hate slipping around in heavy rain and/or snow... had a '64 Caddy Coupe many years ago... turned into sled one night on me because it had lousy tires... that won't happen again..... regarding the Mustang parts recommendation..... is there a year range that goes with that? .....Ps. I just got the car recently... it's solid, no rust, clean, 60k miles, like it just rolled out of a garage in '65 or so and was on it's way to the grocery store... I plan on "driving" it.

...Ps. again..... they're both "Best Answers"... oh hey! ...while I'm thinking... how 'bout electronic ignition conversion kits, any recommendations, preferences?

For the brakes and almost anything else, you are looking at the first generation Mustang, so 65 through 67, for sure. Other years through 73 will also have some parts that interchange. The good news is that almost everything for a Mustang is readily available, so mechanical parts are dirt cheap and easy to get new. Ford got 6 different car lines of that one platform, too. The original Falcon and the Mercury Comet were the compacts. The Ford Fairlane and Mercury Meteor were the 'senior compacts' that became intermediates. Canada also had the Frontenac for 1960 until the Comet came here. Then there was the Mustang. There were a LOT of those cars made, so parts are really very easy. I would talk to the Mustang people about the switch to electronic ignition. It should be simple enough to do as later versions of the 200 I-6 did have it from the factory.

Thanks again... for the additional information... I'll make a shopping list, and then take my time finding what I need "dirt cheap". I'm researching aftermarket electronic ignition conversion kits, and I believe Pertronix is the way to go. They have several models listed for the inline 6. I'm waiting to hear back from them regarding what model will fit my application. I've read nothing bad about them thus far, and only good.

Hey Tennisshoes, I'm going to get the number and speak with the guy who was the previous owner of my previous owner... because my previous owner has incomplete information. I did fiind out that the exhaust manifold gasket was replaced, and that the car had a tune-up including some carb work, in 2010. I'm also going to ask what happened to the original radio... it was replaced with the worst, most generic, cassette/AM/FM deck I've ever seen. I'd like to put the original back and just use something portable like one of those mini apple ipod things or something like that, if I want to listen to music... I can live and drive just fine without it.

For the stereo, go to Classic Autosound. You will get a great modern head unit that will fit right in the dash opening, no cutting needed, and it has an input for a usb as well as an MP3 player.They also have a variety of speaker mounts to make the installation invisible without a close look, and very good sound, too.